ELECTRICAL POWER DISTRIBUTION SYSTEMS WITH A BYPASS UNIT THAT COUPLES TO A LOAD AND ELECTRICALLY ENGAGES ONE OF TWO ALTERNATE UNITS FOR POWERING THE LOAD AND RELATED METHODS

Abstract

Electrical power distribution systems with a bypass unit that electrically engages one of two alternate units for powering a load while electrically isolating the other using a power transfer switch with first and second contactors and mechanical and electrical interlocks to allow a technician to access one of the alternate units when de-energized and in position while the other of the alternate units is energized and powering the load.

Claims

1. (canceled)

2. An electrical power distribution system comprising: a bypass unit configured to selectively couple a load to either a first unit or a second unit, wherein the first unit comprises a first circuit breaker and a first disconnect switch configured to selectively couple a power bus to the bypass unit, and the second unit comprises a second circuit breaker and a second disconnect switch configured to selectively couple the power bus to the bypass unit, wherein the bypass unit comprises a control system configured to: detect fault conditions in the first or second units, and selectively transfer the load between the first unit and the second unit in response to the detected fault conditions.

3. The electrical power distribution system of claim 2, wherein the control system is further configured to automatically isolate a faulted unit by opening a corresponding circuit breaker before transferring the load to the other unit.

4. The electrical power distribution system of claim 2, wherein the bypass unit further comprises a manual override control that allows an operator to manually select the first unit or second unit for powering the load.

5. The electrical power distribution system of claim 2, wherein the control system includes sensors that monitor temperature, voltage, and current within the first and second units to detect the fault conditions.

6. The electrical power distribution system of claim 2, wherein the fault conditions detected by the control system include overload, short-circuit, or ground fault events in the first or second unit.

7. The electrical power distribution system of claim 2, wherein the bypass unit further comprises auxiliary relays configured to communicate status signals to an external monitoring system regarding a status of the first and second units and any detected fault conditions.

8. The electrical power distribution system of claim 2, wherein the bypass unit includes a user interface that provides real-time information about fault conditions and operational statuses of the first and second units.

9. The electrical power distribution system of claim 2, wherein the control system is configured to transmit a trip signal to the circuit breaker of the faulted unit prior to transferring the load to the other unit.

10. The electrical power distribution system of claim 2, wherein the control system is programmed to implement a pre-determined load shedding sequence to reduce power consumption in response to certain fault conditions in either unit.

11. The electrical power distribution system of claim 2, wherein the bypass unit is further configured to initiate a self-diagnostic test on the first and second units when no load is connected to ensure operational readiness before transferring the load.

12. An electrical power distribution system comprising: a bypass unit configured to selectively couple a load to either a first unit or a second unit; wherein the first unit comprises a first disconnect switch and a first circuit breaker, and the second unit comprises a second disconnect switch and a second circuit breaker, each configured to selectively couple a power bus to the bypass unit; wherein the first unit, the second unit, and the bypass unit are each independently housed in separate compartments and are configured for modular installation and removal from the electrical power distribution system, and wherein the bypass unit is configured to maintain uninterrupted power to the load during the removal or replacement of the first unit or the second unit.

13. The electrical power distribution system of claim 12, further comprising an integrated safety interlock system that prevents access to any compartment containing an energized unit.

14. The electrical power distribution system of claim 12, wherein the bypass unit comprises mechanically interlocked first and second contactors, such that only one of the first or second units is coupled to the load at any given time.

15. The electrical power distribution system of claim 12, wherein the first unit, the second unit, and the bypass unit each include a housing with extendable and retractable power stabs that connect to and disconnect from the power bus when installed or removed.

16. The electrical power distribution system of claim 12, wherein the bypass unit includes a load-side circuit breaker, positioned proximate to the power transfer switch relative to the first and second units, to provide additional protection to the load.

17. The electrical power distribution system of claim 12, wherein the bypass unit further comprises an auxiliary switch that automatically transmits a control signal to the circuit breaker of the first or second unit during the transfer of the load to facilitate isolation.

18. The electrical power distribution system of claim 12, wherein the first and second units include interlocks that prevent their removal from the system unless their respective circuit breakers are in an open state.

19. The electrical power distribution system of claim 12, wherein the bypass unit comprises status indicators for each unit, configured to indicate whether the first or second unit is powering the load or is in an isolated state.

12. The electrical power distribution system of claim 12, wherein the bypass unit further includes a backup power source configured to maintain power to the control system and the load during a primary power failure.

21. The electrical power distribution system of claim 12, wherein the bypass unit is configured to provide remote monitoring and control capabilities, allowing an external operator to monitor status and control the operation of the bypass unit, first unit, and second unit via a network interface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 is a schematic diagram of an exemplary electrical power distribution system according to embodiments of the present invention.

[0045] FIG. 2A is a schematic illustration of an exemplary bypass unit according to embodiments of the present invention.

[0046] FIG. 2B is a front, side perspective view of the bypass unit shown in FIG. 2A according to embodiments of the present invention.

[0047] FIG. 2C is a rear, side perspective view of the bypass unit shown in FIG. 2A according to embodiments of the present invention.

[0048] FIGS. 3A, 3B, and 3C are box diagrams of electrical distribution systems according to embodiments of the present invention.

[0049] FIGS. 4-6 are schematic illustrations of electrical distribution systems according to embodiments of the present invention.

[0050] FIG. 7A is an enlarged front view of a transfer switch and deadfront switch handle suitable for the bypass unit shown in FIG. 2B according to embodiments of the present invention.

[0051] FIG. 7B is a schematic illustration of an electrical distribution system according to embodiments of the present invention.

[0052] FIG. 8 is a partial front side perspective view of a motor control center (MCC) according to embodiments of the present invention.

[0053] FIG. 9 is a top, side perspective view of an example unit with power stabs according to embodiments of the present invention.

[0054] FIG. 10 is a bottom view of the example unit shown in FIG. 9 according to embodiments of the present invention.

[0055] FIG. 11 is a table of actions/conditions an electrical interlocking system for electrical distribution systems according to embodiments of the present invention.

[0056] FIG. 12 is a table of actions/conditions for a mechanical interlocking system according to embodiments of the present invention.

[0057] FIG. 13A is a partial front view of a front panel segment of an example unit with a keyed interlock according to embodiments of the present invention.

[0058] FIG. 13B is a top view of the device shown in FIG. 13A.

[0059] FIG. 14A is an enlarged view of the keyed interlock shown in FIG. 13A.

[0060] FIG. 14B is an enlarged view of a mechanically locked slide of a unit of the MCC shown in FIG. 8.

[0061] FIG. 15 is a schematic illustration of an electrical distribution system with a power transfer switch having first and second contactors in combination with a manually engageable back-up bypass path according to embodiments of the present invention.

[0062] FIG. 16 is a front perspective view of another embodiment of a bypass unit suitable for the electrical distribution system shown in FIG. 15 according to embodiments of the present invention.

[0063] FIG. 17 is a partial front view of a bypass unit suitable for the electrical distribution system shown in FIG. 15 according to embodiments of the present invention.

[0064] FIG. 18 is a top schematic view of a bypass unit with a mechanical interlock suitable for the electrical distribution system shown in FIG. 15 according to embodiments of the present invention.

[0065] FIG. 19A/19B is a flow chart of actions that can be carried out to power a load according to embodiments of the present invention.

[0066] FIG. 20 is a flow chart of an example build process allowing for end user builds from a defined set of modular unit options according to embodiments of the present invention.

[0067] FIG. 21 is a flow chart of example actions that can be used to power a load according to embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0068] The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. Like numbers refer to like elements and different embodiments of like elements can be designated using a different number of superscript indicator apostrophes (e.g., 10, 10, 10, 10).

[0069] In the drawings, the relative sizes of regions or features may be exaggerated for clarity. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0070] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

[0071] Spatially relative terms, such as beneath, below, lower, above, upper and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device or system in use or operation in addition to the orientation depicted in the figures. For example, if the device or system in the figures is turned over, elements described as below or beneath other elements or features would then be oriented above the other elements or features. Thus, the exemplary term below can encompass both an orientation of above and below. The device or system may be otherwise oriented (rotated 90 or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0072] The term about, when used with a number, refers to numbers in a range of +/20% of the noted value(s).

[0073] As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms includes, comprises, including and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being connected or coupled to another element, it can be directly connected or coupled to the other element or intervening elements may be present. As used herein, the term and/or includes any and all combinations of one or more of the associated listed items.

[0074] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0075] The terms operating mechanism and operator mechanism are used interchangeably and refer to an assembly that is a primary disconnect for a unit and typically has a manually operative lever for opening and closing separable contacts in a circuit breaker and/or for turning power ON and OFF using a switch associated with a fuse (e.g., a fused disconnect). When a disconnect switch (e.g., circuit breaker) of the operator mechanism is ON and connected to a power bus, the unit is energized.

[0076] The terms bucket assembly, bucket, control unit, and unit are used interchangeably and refer to a housing (typically a protective metal shell) that contains a disconnect switch, such as an isolation switch (for a bypass unit), a fused disconnect switch, or a circuit breaker (which can be manually operated by an operator mechanism) for controlling energization/de-energization of the power circuit in the unit. A unit can also include other components such as a power transformer, PLCs (programmable logic controllers), position sensors and the like.

[0077] The unit can be a motor starter unit, a feeder unit, a unit with a transfer switch or any other unit type. The term motor starter is used herein to refer to any starter type. The motor starter can be, for example, a variable frequency drive (VFD) (also known as a variable speed drive), a soft starter (reduced voltage starter), a NEMA starter (NEMA contactor and overload relay, or an IEC starter (IEC contactor and overload relay). The unit can comprise a feeder such as a feeder with a circuit breaker (feeder breaker) or a feeder with a disconnect switch with a fuse (feeder with fused disconnect switch), a lighting contactor, a resistive contactor or an ATS (automatic transfer switch), by way of further example.

[0078] The term disconnect switch when used with respect to a unit refers to a switch in or on the unit for controlling energization or de-energization of the unit, including a circuit breaker or a switch for opening and closing separable contacts in, e.g., a circuit breaker and/or for turning power ON and OFF using a switch associated with a fuse (e.g., a fused disconnect).

[0079] The terms load and load device are used interchangeably and are intended to mean devices that consume electrical power and that are connected to and controlled by the electrical power distribution system (e.g., a motor control center). Load devices are typically motors but may also be pumps or other machinery that may comprise motors or pumps or other miscellaneous critical loads such as hospitals, dam emergency pumps, data centers, back-up generator systems and the like.

[0080] Referring to FIG. 1, one embodiment of an electrical power distribution system 100 (e.g., a motor control center) is shown. The electrical power distribution system 100 includes a bypass unit 10 with a power transfer circuit 20, a first unit 50.sub.1 and a second unit 50.sub.2. As shown, the electrical power distribution system 100 includes a structure with compartments 110, a wire way 100w (FIG. 4, for example), a power bus 200, units 50.sub.1, 50.sub.2 and a bypass unit 10 for providing power from the power bus 200 of a power bus bar system 1000 (FIG. 7B, for example) to an external load 80. The electrical power distribution system 100 can include more than two units 50.sub.1, 50.sub.2 and the bypass unit 10 as shown in FIG. 8, for example.

[0081] Embodiments of the invention can allow for electrical isolation of one of the units 50.sub.1, 50.sub.2, from the other of the units 50.sub.1, 50.sub.2, while the other unit is operational, online, and providing power to the load 80, thereby providing a continuous operational system while also providing increased safety for a technician. For example, since the primary or first unit 50.sub.1 is electrically isolated from the secondary or second unit 50.sub.2, a technician can access the first unit 50.sub.1 which is offline and electrically isolated from the second unit 50.sub.2, the power bus 200 (FIGS. 1, 4) and the load 80, while the second unit 50.sub.2 is operational, online, and providing power to the load 80, thereby providing a continuous operational system while also providing increased safety for a technician.

[0082] Embodiments of the invention can also provide for physical separation/isolation of the first and second units 50.sub.1, 50.sub.2 and the bypass unit 10 from each other in compartments 110 of the structure 100 using barriers such as partitions, walls, ceilings and floors, for example.

[0083] Referring to FIG. 2A, an example bypass unit 10 is shown. As shown, the bypass unit 10 includes a housing 10h that encloses the power transfer circuit 20 which comprises a power transfer (bypass) switch 25. The power transfer circuit 20 is coupled to a load 80, such as a motor 80m, via a conductor 30, shown as a three pole/three phase lead with three electrical contact connections. The term conductor refers to one or more cables, each of which can include one or more wires, leads or other elements that conduct electricity, or one or more wires, leads, traces, lines or other elements that conduct electricity.

[0084] The power transfer circuit 20 is also electrically coupled to a first unit 50.sub.1 and a second unit 50.sub.2 (FIGS. 1, 3A, 3B, 4-6) via conductors 32, 34, respectively, and is configured to only electrically connect the load 80 to a single one unit of the first unit 50.sub.1 or the second unit 50.sub.2 at any one time during normal operation. The conductors 30, 32, 34 can be of the same or different lengths. The conductors 32, 34 can extend from the bypass unit 10 to the first and second units 50.sub.1, 50.sub.2, inside a wire way 100w of a structure 100, such as an MCC 100M (FIGS. 4-6).

[0085] Referring to FIGS. 2A and 4-6, the power transfer circuit 20 of the bypass unit includes a power transfer switch 25. The power transfer switch 25 comprises a mechanical interlock 125 (FIG. 7A) that mechanically interlocks the first and second contactors 26.sub.1, 26.sub.2, respectively, so that the power transfer switch 25 is configured to electrically couple to the load 80 and define a first electrical path P.sub.1 and a second electrical path P.sub.2 where only one of the first and second contactors 26.sub.1, 26.sub.2 close at any one time.

[0086] As shown, the bypass unit 10 can also include a circuit breaker 29 in the bypass unit 10 that is coupled to a load side of the power transfer switch 25 and also coupled to the first electrical path P.sub.1 inside the bypass unit 10 between the line side of the power transfer switch 25 and the first unit 50.sub.1 to thereby inhibit (electrical) feedback to an electrically isolated unit, i.e., the second unit 50.sub.2 when the first electrical path Pi is active.

[0087] As shown in FIG. 2B, the circuit breaker 29 typically has an externally accessible operator handle 230 that faces a front 10f of the bypass unit 10 and is configured to be externally accessible to allow a user to lock the operator handle 230 in a desired operational state, using a lock such as a padlock or scissors lock. For example, a user can lock the operator handle 230 in an OFF position associated with non-conduction in the first electrical path P.sub.1 while the bypass unit 10 provides power to the load 80 from the power bus 200 to the second unit 502 through the second path P.sub.2, then the second contactor 262 of the switch 25, then to the load 80.

[0088] As shown in FIGS. 2B and 2C, the bypass unit 10 has a front panel 10f, sidewalls 10s, a ceiling 10c, a floor 10b and a back wall 10r that defines an enclosed compartment 11 and does not require, and typically does not have, power stabs (for engaging a power bus) that extend out from the back wall 10r. A plurality of conductors 30, 32, 34 extend out of the housing 10h, typically one of the side walls 10s, shown as the right side wall 10e (FIG. 2C). The term right side refers to the orientation when held in a structure for normal operation with the front 10f facing forward. The incoming wires (e.g., nine wires, three associated with each conductor 30, 32, 34) can be fed into the bypass unit 10 through one side of the unit and into a wire way 100w (FIG. 4) and the rear 10r of the housing 10h can be a closed panel. The bypass unit 10 can electrically isolate each of the first unit 50.sub.1 and the second unit 50.sub.2 from the load 80 and/or from each other while respective front panels 50f (FIGS. 1, 3A, 3B) remain closed and typically locked in the closed position.

[0089] In some embodiments, the housing 10h of the bypass unit 10 can define an enclosure with a solid back wall 10r with the conductors 30, 32, 34 extending from a common portion or different portions of the housing 10h via a ceiling, floor, sidewall or back wall. The housing 10h can be a 1 size housing (about 6 inches tall) or a 2 size housing (about 12 inches tall) in some embodiments.

[0090] As shown in FIG. 2B, the bypass unit 10 can include a (pilot) control switch 15 to electrically activate an automatic bypass mode of the unit 10 whereby the power transfer switch 25 engages the second electrical path P.sub.2 and the second contactor 26.sub.2 of the switch 25 and second unit 50.sub.2. The control switch 15 allows a user to manually activate the automatic bypass switch 25 of the power transfer circuit 20 to automatically electronically transfer to a bypass mode transferring power from the power bus 200 to the primary or first unit 50.sub.1 through the first path Pi of the bypass switch 25 to the load 80 is switched from the power bus 200 to the bypass or second unit 50.sub.2 through the second path P.sub.2 and the second contactor 26.sub.2 of the bypass switch 25 to the load 80. Example relay logic protocols are discussed below that can automatically initiate the power transfer to the second path P.sub.2 if the main/primary/first unit fails. A controller and/or relay system 1510 (FIG. 7B) can, upon detection of a defined condition associated with a malfunction or failure of the first unit 50.sub.1, direct the power transfer circuit 20 to engage the second contactor 26.sub.2 and disengage the first contactor 26.sub.1 to power the load 80 through the second unit 50.sub.2.

[0091] It is contemplated that embodiments of the invention can comply with the recommendation of IEEE P1814 with respect to a reduced hazard requirement which recommends a drive unit, such as a VFD unit, be isolated. Embodiments of the invention can provide a bypass unit that couples to both primary and secondary (redundant) units with respective motor starters of the same or different motor starter types. Embodiments of the invention provide modular build options without requiring expensive, complex and larger cumbersome customizations for providing different build configurations while providing the bypass power transfer function.

[0092] Embodiments of the invention can allow for electrical isolation of one of the units 50.sub.1, 50.sub.2, from the other of the units 50.sub.1, 50.sub.2, while the other unit is operational, online, and providing power to the load 80, thereby providing a continuous operational system while also providing increased safety for a technician. For example, since the primary or first unit 50.sub.1 is electrically isolated from the secondary or second unit 50.sub.2, a technician can access the first unit 50.sub.1 which is offline and electrically isolated from the second unit 50.sub.2, the power bus 200 (FIGS. 1, 4) and the load 80, while the second unit 50.sub.2 is operational, online, and providing power to the load 80, thereby providing a continuous operational system while also providing increased safety for a technician.

[0093] Referring to FIG. 2B, the handle 230 can be a lever or handle of an operator mechanism that can be physically moved and configured to engage a lock so as to be able to be physically locked (e.g., padlocked) in an OFF or ON position, ON for when unit one 50.sub.1 is energized, connected to the power bus 200/1000 and to the first contactor 26.sub.1 to power the load 80 through the first unit 50.sub.1 and OFF for when the second unit 50.sub.2 is energized, connected to the power bus 200/1000 and to the second contactor 26.sub.2 to power the load through the second unit 50.sub.2. The handle 230 can include, e.g., a rotary lever or an up-down lever.

[0094] Still referring to FIG. 2B, the bypass unit 10 can also optionally include a lock 13 that locks the front panel 10f (which can be a front door that pivots open from a side) closed so that a technician cannot open the front panel or door 10f when the lock is deployed. The lock 13 can be a physical/mechanical interlock that locks the front panel or door 10f in a closed position.

[0095] One or all of the units 10, 50.sub.1, 50.sub.2 (FIGS. 1, 3A, 3B) can be configured as a modular unit to allow the internal components to be assembled as a unit 10, 50.sub.1, 50.sub.2 that can be easily, typically slidably and replaceably, installed into a compartment 110 of a structure 100 (FIGS. 1, 3A, 3B) such as an enclosure, a cabinet, and/or a motor control center (MCC) 100M (FIGS. 4-6). Embodiments of the invention provide modular (plug and play) configurations which can provide economic advantages to known conventional custom bypass designs that are cumbersome and may not provide the additional electrical isolation allowed by embodiments of the present invention. To be clear, the term modular refers to units that have defined standardized dimensions so that one unit of one type is replaceably interchangeable with another unit of that type.

[0096] Referring again to FIG. 2B, the bypass unit 10 can be provided in package or frame sizes of about 6 inches to about 72 inches (tall) in a height dimension H with substantially common depth and width dimensions, known as 1 (6 inches) to 12 (72 inches) sizes. The sizes can be in single X increments, from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12. Thus, a 5 unit 10 can be about 30 inches tall. In some embodiments, the bypass unit 10 can be a 1 unit with a height H of about 6 inches or a 2 unit with a height H of about 12inches. The frame sizes can be provided for target operational amperages, including a plurality of: 125 A, 150 A, 225 A, 250 A, 400 A, 600 A, 1200 A and 2000 A, for example.

[0097] FIGS. 1, 3A, 3B illustrate that the bypass unit 10 can be placed in a compartment 110 of a structure of the power distribution system 100 and electrically coupled to the first unit 50.sub.1 and the second unit 50.sub.2. The first and second units 50.sub.1, 50.sub.2 can each include a respective motor starter 50m (FIGS. 4-6) and a respective disconnect switch 60. Each unit 50.sub.1, 50.sub.2 can include a front panel or door 50f.

[0098] The front door 50f of each unit 50.sub.1, 50.sub.2 may be configured to engage at least one lock 53 that, when deployed, can lock the door 50f in the closed position. The lock 53 can be a physical mechanical interlock.

[0099] As shown in FIGS. 1, 3A, 3B, a conductor 50.sub.2 can couple the first and second units 50.sub.1, 50.sub.2 and can allow the first unit 50.sub.1 can transmit a trip signal to the disconnect switch 60 (e.g., circuit breaker) of the second unit 50.sub.2 when the first unit 50.sub.1 is selected by the power transfer circuit 20 via the power transfer switch 25 to create the electrical path to power the load 80 via the bypass unit 10. Likewise, the second unit 50.sub.2 can transmit a trip signal to the disconnect switch 60 (e.g., circuit breaker) of the first unit 50.sub.1 when the second unit 50.sub.2 is selected by the power transfer circuit 20 via the bypass switch 25 to create the electrical path to power the load 80 via the bypass unit 10. This can provide an extra degree of safety via an electrical interlock system.

[0100] In some embodiments, each disconnect switch 60 of the first and second units 50.sub.1, 502 includes a circuit breakers 60b with a shunt trip 60s as shown schematically in FIG. 7B. The terms shunt trip and shunt trip coil are used interchangeably herein and are well known components of circuit breakers.

[0101] The power transfer switch 25 of the bypass unit 10 can be configured with open and close switch states of each switch contact 26c (FIG. 2A) so that only one set of three switch contacts/poles is electrically active and connected to one of the first and second units 50.sub.1, 50.sub.2 at any one time to serially provide a first electrical path P.sub.1 between a power bus 200 (FIG. 4), the first unit 50.sub.1, the bypass unit 10, and the load 80 and a second electrical path P.sub.2 between the power bus 200, the second unit 50.sub.2, the bypass unit 10, and the load 80.

[0102] The bypass unit 10 can be configured to provide automatic power transfer (bypass) using a reverse contactor without an overload that is mechanically coupled.

[0103] Referring to FIGS. 3A, 3B and 7B, the disconnect switch 60 of the first unit 50.sub.1 can electrically couple to the disconnect switch 60 of the second unit 50.sub.2. In some embodiments, the disconnect switch 60 of each of the units 50.sub.1, 50.sub.2 comprises a circuit breaker 60b. In certain defined conditions, the first unit 50.sub.1 can send a trip signal to the circuit breaker 60b of the second unit 50.sub.2 to cause the breaker shunt trip coil 60s to trip the breaker 60b in the second unit 50.sub.2. In certain defined conditions, the second unit 50.sub.2 can send a trip signal to the circuit breaker 60 of the first unit 50.sub.1 to cause the breaker shunt trip coil 60s to trip the breaker 60b in the first unit 50.sub.1.

[0104] Referring to FIGS. 1, 2A, 2B, 3A, 3B, a conductor 502 can be coupled to the first and second units 50.sub.1, 50.sub.2 to permit signal communication therebetween, to thereby provide electrical interlocking functionality. For example, when a user selects the first unit 50.sub.1 to power the load by switching the user interface member 130 (e.g., operator handle of an operator mechanism) to an ON position and switching the isolation bypass switch 25 to Unit 1-ON position, the first unit 50.sub.1 (either or both the auxiliary switch of the circuit breaker 60b or the auxiliary relay 150r of the motor starter 50m) can transmit a trip signal to the circuit breaker 60b of the second unit 50.sub.2, typically via the shunt trip 60s (FIG. 7B). Likewise, the second unit 50.sub.2 can transmit a trip signal to the circuit breaker 60b of the first unit 50.sub.1, typically the shunt trip 60s (FIG. 7B), when the second unit 50.sub.2 is selected by the power transfer circuit 20 via the isolation bypass switch 25 to create the electrical path to power the load 80 via the bypass unit 10. This can provide an extra degree of safety via an electrical interlock system.

[0105] Referring to FIGS. 3A, 3B and 7B, the disconnect switch 60 of the first unit 50.sub.1 can electrically couple to the disconnect switch 60 of the second unit 50.sub.2. In some embodiments, the disconnect switch 60 of each of the units 50.sub.1, 50.sub.2 comprises or is a circuit breaker 60b. In certain defined conditions, the first unit 50.sub.1 can send a trip signal to the circuit breaker 60 of the second unit 50.sub.2 to cause the breaker shunt trip coil 60s to trip the breaker in the second unit 50.sub.2. In certain defined conditions, the second unit 502 can send a trip signal to the circuit breaker 60b of the first unit 50.sub.1 to cause the breaker shunt trip coil 60s to trip the breaker in the first unit 50.sub.1.

[0106] The first unit 50.sub.1, for ease of discussion can be referred to as a primary unit, and a second unit 50.sub.2, for ease of discussion can be referred to as a secondary unit that can be coupled to the bypass unit 10 for selectively powering a load 80 through the power transfer circuit of the bypass unit 10.

[0107] In some embodiments, an electrical power distribution system 100 (e.g., MCC) can include a plurality of different electrical interlocks to ensure that only one unit of units 50.sub.1, 50.sub.2 is energized and capable of providing power to the load 80 through the bypass unit 10 at any one time. FIG. 11 lists exemplary electrical interlocks. These defined conditions and associated actions can provide an electrical interlock system. FIG. 11 lists example actions of the first (primary) unit 50.sub.1, the second (redundant) unit 50.sub.2, and the bypass unit 10 providing an electrical interlocking system based on defined operative conditions or states of the first and second units 50.sub.1, 50.sub.2.

[0108] Example interlocks associated with a primary mode (when the first unit 50.sub.1 is powering the load 80 through the bypass unit 10) or a bypass mode (when the second unit 50.sub.2 is powering the load 80 through the bypass unit 10) are listed. The defined conditions can include positions of power stabs 554 optionally provided as retractable/extendable power stabs 546, 548, 550 of a power disconnect assembly 500 (FIGS. 9 and 10) whether the power stabs 546 are fully extended and connected to a power bus 1000 or retracted (FIGS. 4-6) based on position sensors 582, 594 such as one or more microswitches (FIG. 10) in the respective units 50.sub.1, 50.sub.2. Other conditions can be based on an energized status of a respective primary or secondary unit based on an auxiliary switch and/or auxiliary relay in each of the first and second units which can send a trip signal to the other unit. The bypass unit 10 can also send a trip signal to the primary 50.sub.1 or secondary unit 50.sub.2 depending on whether the bypass unit 10 is in the primary mode (trip signal to the secondary unit) or the bypass mode (trip signal to the primary unit).

[0109] However, while the power disconnect assembly 500 is believed to be desired for certain end applications/uses, it is not required. For further description of position sensors using auxiliary switches such as microswitches in a unit with a power disconnect assembly 500, see U.S. 2008/0022673 (labeled as features 82 and/or 94 in FIG. 17 of this document), the contents of which are hereby incorporated by reference as if recited in full herein. For further descriptions of example power disconnect assemblies and interlocks, see also, U.S. patent application Ser. No. 15/848,103, the contents of which are hereby incorporated by reference as if recited in full herein.

[0110] Table 1 below provides a list of example configurations of the first unit 50.sub.1, for ease of discussion referred to as a primary unit, and a second unit 50.sub.2, for ease of discussion referred to as a secondary unit, that can be coupled to the bypass unit 10 for serially (selectively) powering a load 80 through the power transfer circuit of the bypass unit 10.

TABLE-US-00003 TABLE 1 UNIT COMBINATION OPTIONS Option Primary Unit Secondary unit A VFD unit VFD unit B Soft Starter Soft Starter (Reduced Voltage (Reduced Voltage starter) unit starter) unit C NEMA Starter unit NEMA Starter unit D IEC Starter unit IEC Starter unit E VFD unit Soft Starter (Reduced Voltage starter) unit F Soft Starter NEMA Starter unit (Reduced Voltage starter) unit G NEMA Starter unit IEC Starter unit H VFD unit NEMA Starter unit I Soft Starter IEC Starter unit (Reduced Voltage starter) unit J VFD unit IEC Starter unit K Feeder Breaker Feeder Breaker L Feeder Fused Feeder Fused

[0111] Referring to FIG. 7B, the trip signal for the electrical interlock system can be generated/transmitted via at least one interlock circuit 1500 that can include auxiliary switch inputs from one or more auxiliary switches 27 in the bypass unit 10 via conductor lead 127 and disconnect switch inputs from the first and second units 50.sub.1, 50.sub.2 via conductor lead 502, for example.

[0112] Referring to FIG. 7B, the trip signal for the electrical interlock system can be generated/transmitted via at least one interlock circuit 1500 that can include (a) one or more inputs for receiving a signal from an auxiliary switch 27 (FIG. 7A) of the bypass unit 10 via conductor 127 and (b) one or more input(s) for receiving a signal from the first and second units 50.sub.1, 50.sub.2 such as from an auxiliary switch or contact associated with the circuit breaker 60b of the disconnect switch 60 and/or an auxiliary relay 150r coupled to or in the motor starter 50m. As discussed above, the first and second units 50.sub.1, 50.sub.2 can be coupled via a conductor 502, for example. One or more of the outputs/signals from the auxiliary switch 27 and/or the interlock circuit 1500 can provide a voltage signal as a trip signal to a shunt trip 60s in a circuit breaker 60b of one of the first and second units 50.sub.1, 50.sub.2 when the other unit of the first and second units 50.sub.1, 50.sub.2 has a circuit breaker 60b that is energized.

[0113] Still referring to FIG. 7B, each motor starter 50m can be coupled to an auxiliary relay 150r that can transmit a trip signal 150s to the interlock control circuit 1500. For example, when a motor starter 50m of one of the first and second units first and second units 50.sub.1, 50.sub.2 is on and/or operating, an auxiliary relay 150r can transmit a voltage trip signal 150s to the circuit breaker 60b of the other unit to make sure that the other unit is off, contacts open, as a safety interlock feature.

[0114] In some embodiments, the auxiliary relay 150r of the motor starter (e.g., soft starter) 50m, the auxiliary switch 27 of the bypass unit 10 and an auxiliary switch 60s in the breaker 60b of first unit 50.sub.1 can be synchronized and/or transmit in parallel, trip signals to the second unit 50.sub.2 when the first unit 50.sub.1 is energized. The auxiliary relay 150r of the motor starter (e.g., soft starter) 50m, the auxiliary switch 27 of the bypass unit 10 and the auxiliary switch 60s in the breaker 60b of the second unit 50.sub.2 can be synchronized and/or transmit in parallel trip signals to the first unit 50.sub.1 when the second unit 50.sub.2 is energized.

[0115] The term auxiliary switch for the primary unit and the secondary unit in FIG. 11 that can send the trip signal(s) to the appropriate breaker can include one or more auxiliary switches including, for example, an auxiliary switch 582, 594 (FIG. 10) identifying a position of the retractable/extendable power stabs, an auxiliary switch of a circuit breaker 60b (FIG. 7B) associated with a contacts closed condition, or an auxiliary relay 150r (FIG. 7B) of a motor starter 50m indicating an motor on condition.

[0116] The structure 100 can be designed to slidably receive multiple units 10, 50.sub.1, 50.sub.2 in various defined sizes. For example, the first and second units 50.sub.1, 50.sub.2 can each have housings 50h of the same or different modular heights (i.e., 1-12 frame sizes as discussed above). Each housing 10h, 50h can include a front door 10f, 50f that can remain closed when a respective unit is energized. Only one of the two units 50.sub.1, 50.sub.2 can be energized when connected to the power bus bars 200 and connected to the load 80 via the bypass unit 10 at any one time. When in a de-energized state, the front door 50f of only that de-energized unit, one of the two units 50.sub.1, 50.sub.2, can be opened to allow a technician access to replace or repair that unit while the other of those two units 50.sub.1, 50.sub.2 is energized, connected to the power bus and load while the de-energized unit is electrically isolated from the energized unit and the bypass unit 10.

[0117] FIG. 3A illustrates that the bypass unit 10 can be placed in a first structure 100.sub.1 while the first unit 50.sub.1 and the second unit 50.sub.2 are in a separate, but typically adjacent, structure 100.sub.2. Each structure 100 can optionally have a front door 100f (shown by the shading over the respective units) that closes and releasably locks via at least one mechanical lock 114 in the closed position over one or more of the units 50.sub.1, 50.sub.2 and 10, respectively.

[0118] FIGS. 3B and 1 illustrate that the bypass unit 10 and the first and second units 50.sub.1, 50.sub.2 are held in the same structure 100. FIG. 3B illustrates that the units 50.sub.1, 50.sub.2 can be held in side by side, laterally adjacent compartments 110. FIG. 1 illustrates that the bypass unit and the first and second units 50.sub.1, 50.sub.2 can be held in a vertically stacked arrangement of compartment 110.

[0119] Referring to FIG. 1, each compartment 110 can have a closed floor 110f and/or ceiling and/or rails 112 coupled to internal sidewalls 110i that slidably receive and support the units 10, 50.sub.1, 50.sub.2.

[0120] Referring to FIGS. 4-6, the first and second units 50.sub.1, 50.sub.2 can have power stabs 554 extending rearward from the back 50r that connect to one or more (typically vertically oriented) power bus bars 200 that are part of a power bus system 1000 that carries power (current) to the compartments of a vertical section in the structure such as the MCC 100M. These power stabs 554 may optionally be provided by a power disconnect assembly 500 as discussed above. As is well known, the bus bars 200 can be connected to larger (typically horizontal bus bars) that bring power to the vertical sections. The larger (typically horizontal) bus bars are usually in the top, but some structures may have them in the center or bottom. The structures of MCCs 100M usually have at least one wire way 100w for conductors 30, 32, 34 (i.e., wires) to the load(s) and control wires.

[0121] FIG. 4 illustrates an MCC 100M with the bypass unit 10 and a first unit 50.sub.1 that can comprise a VFD 50.sub.VFD as the motor starter 50m and can also comprise power stabs 554, shown as provided by a power disconnect assembly 500. FIG. 4 also illustrates that the second unit 50.sub.2 can comprise a NEMA starter 50.sub.Nm as the motor starter 50m and can also comprise power stabs 554, shown as provided by a power disconnect assembly 500. The microswitches 582 and/or 594 (FIG. 10) can identify when the stabs 554 are fully engaged to the (vertical) power bus 200 and when the stabs 554 are fully withdrawn and isolated from the (vertical) bus 200.

[0122] FIG. 5 illustrates an MCC 100M with the bypass unit 10 and a first unit 50.sub.1 that can comprise a soft starter 50ss as the motor starter 50m and can also comprise power stabs 554, shown as provided by a power disconnect assembly 500. FIG. 5 also illustrates that the second unit 50.sub.2 can comprise a NEMA starter 50.sub.Nm as the motor starter 50m and can also comprise power stabs 554, shown as provided by a power disconnect assembly 500. The position sensors 582 and/or 594 (FIG. 10) can identify when the stabs 554 are fully engaged to the (vertical) power bus 200 and when the stabs 554 are fully withdrawn and isolated from the (vertical) power bus 200.

[0123] FIG. 6 illustrates an MCC 100M with the bypass unit 10 and a first unit 50.sub.1 that can comprise a VFD 50.sub.VFD as the motor starter 50m and can also comprise power stabs 554, shown as provided by a power disconnect assembly 500. FIG. 6 illustrates that the second unit 502 can comprise a soft starter 50ss as the motor starter 50m and can also comprise power stabs 554, shown as provided by a power disconnect assembly 500. The position sensors (e.g., microswitches) 582 and/or 594 (FIG. 10) can identify when the stabs 554 are fully engaged to the (vertical) power bus 200 and when the stabs 554 are fully withdrawn and isolated from the (vertical) bus 200.

[0124] Thus, as shown by the examples of FIGS. 4-6, modular units 50.sub.1, 50.sub.2 of different motor starter configurations can allow a number of different MCC build selections and/or configurations without requiring unique more expensive custom units.

[0125] Referring to FIG. 7A, the power transfer switch 25 of the bypass unit 10 can comprise a first contactor 26.sub.1 that is mechanically interlocked with a mechanical interlock 125 to the second contactor 26.sub.2. A first set of three contacts 26c coupled to the first unit 50.sub.1 and a second set of three contacts 26c electrically coupled to the second unit 50.sub.2. The contactor can be a double throw contactor. The switch 25 can include a main switch body 25m and one or more auxiliary switches 27, typically at least one auxiliary switch 27 on each opposing end or side of the main switch body 25m. The auxiliary switches 27 can be configured to receive and/or transmit signals from and/or to the first unit 50.sub.1 and the second unit 50.sub.2.

[0126] Referring to FIG. 7B, a relay system 1510 in an MCC 100 can be coupled to one or more of the bypass unit 10, the first unit 50.sub.1, and/or the second unit 50.sub.2 can be used to identify when the first unit 50.sub.1 powers down, malfunctions or turns off, then automatically directly or indirectly sends a trip signal to direct or cause a shunt trip coil in the breaker 29 to trip the breaker 29 and automatically switch the power transfer switch 25 to electrically connect the second unit 50.sub.2. This automatic trip and transfer operation may be particularly suitable for critical loads. Tripping the circuit breaker 29 will electrically isolate the first unit 50.sub.1 as a standard contactor is not an isolation device.

[0127] One or more of the at least one auxiliary switch 27 can transmit a trip signal to the disconnect switch 60 of one of the first unit 50.sub.1 or the second unit 50.sub.2 when the other of the first unit 50.sub.1 or the second unit 50.sub.2 is energized with the stabs 554 contacting the power bus 200. A respective auxiliary switch 27 can be coupled to one or both units 50.sub.1, 50.sub.2 via a conductor 127 (e.g., wire(s)) (FIG. 7B). A trip signal can be transmitted to the circuit breaker 29 to automatically direct the circuit breaker 29 to trip to electrically isolate the first unit 50.sub.1 from the load and the second unit 50.sub.2 when the first unit 50.sub.1 fails or powers down.

[0128] One or more of the at least one auxiliary switch 27 can transmit the trip signal to the circuit breaker 29 in the bypass unit 10 when the first unit 50.sub.1 fails or malfunctions, for example.

[0129] As also shown in FIG. 7B, the first and second units 50.sub.1, 50.sub.2 can be electrically coupled via one or more conductors 50.sub.2 so that the first unit 50.sub.1 can send a trip signal to the second unit 50.sub.2 when the first unit 50.sub.1 is connected to the power bus bars 200.

[0130] The second unit 50.sub.2 can send a trip signal to the first unit 50.sub.1 and the circuit breaker 29 when the second unit 50.sub.2 is connected to the power bus bar 200. In some embodiments, the trip signal can be generated by an auxiliary switch in a respective unit 50.sub.1, 50.sub.2 such as a microswitch assembly associated with a position sensor 594 or 582 (FIG. 10) associated with one of the units with a power disconnect assembly 500 when the stabs of one of the units 50.sub.1, 50.sub.2 are fully extended and the stabs of the other unit are not extended (i.e., are retracted).

[0131] FIG. 7B illustrates that the structure 100, optionally an MCC 100M, can comprise the bypass unit 10 coupled to the first unit 50.sub.1 and the second unit 50.sub.2. Each unit 10, 50.sub.1, 50.sub.2, can be in separate housings 10h, 50h and placed in separate compartments of the structure 100. Each housing 10h, 50h can have a closed front panel or door 10f, 50f.

[0132] FIG. 8 illustrates an example MCC 100M with the first and second units 501, 502 and the bypass unit 10. The first and second units 50.sub.1, 50.sub.2 include operator handles 51 that are coupled to internal disconnect switches 60, such as circuit breakers, as is well known to those of skill in the art. The bypass unit 10 includes the switch handle 230 and a control switch 15 operable through a closed door. The (op-mech) switch handle 230 may be a rotary or up-down handle that is coupled to the power transfer circuit 20 (FIG. 1).

[0133] Still referring to FIG. 8, a typical MCC structure 100M is an enclosure with a number of small doors arranged in rows and columns along the front and flat, mostly featureless, back and sides. The units 10, 50 can be provided in varying sizes. For starter units 50.sub.1, 50.sub.2, the size can be based on the size of the load 80, e.g., motor 80m (FIG. 1) they are controlling. The units 10, 50.sub.1, 50.sub.2 can be configured to be relatively easily removable for repair, service or replacement. MCCs 100M can have different sets of units, for example, regular starters, reversing starters, soft start, and variable frequency drives. MCCs 100M can be configured so that sections can be added for expansion if needed.

[0134] MCCs 100M can be configured in many ways. Each compartment 110 can have a different height to accept different frame sizes of respective bucket assemblies or units 10, typically in about 6-inch increments. The vertical bus can be omitted or not run through the full height of the section to accommodate deeper buckets for larger items like variable frequency drives. The MCC can be a modular cabinet system for powering and controlling motors and/or feeder circuits. Several may be powered from main switchgear which, in turn, gets its power from a transformer attached to the incoming line from a public or private grid, e.g., a power company.

[0135] Referring to FIG. 8, a partial perspective view of a motor control center structure 100M is shown. Units 10, 53, 50.sub.1, 50.sub.2 are shown fully installed into a motor control center compartment 110 such that its respective front panel 10f, 53f, 50f is seated securely against the periphery of the compartment enclosure and flush with the front panel 54f of unit 54 and with the front panel 50f of units 50.sub.1, 50.sub.2.

[0136] In some embodiments, some or all units, e.g., units 53, 50.sub.1, 50.sub.2 can include a number of latching mechanisms 22 on front panels thereof so that an operator may lock a unit into place once installed. In some embodiments, the front panel 50f, 53f may be a deadfront door having a set of hinges 19 in order to permit access to motor control components within a unit while the unit is installed in a compartment 111 of the MCC 100M. However, even when closed or sealed, front panel or door 50f still permits access to the disconnect switch 60 which can comprise a circuit breaker, stab indicator 24, shutter indicator 26, and line contact actuator 31. Line contact actuator 31 is a mechanism of the power disconnect assembly 500 (FIG. 9) for selectively engaging a power bus 200 to engage power stabs 554 defining line contacts (FIG. 4) with line power from the MCC 100M. Thus, even when a unit 10, 50 is fully installed in a compartment 110 and latches 22 have been secured, an operator may still use respective disconnect switch handles 51, 230.

[0137] As shown in FIG. 8, the first unit 501 can have the handle 51 in an ON position associated with conduction and an energized state while the second unit 50.sub.2 has the handle 51 in an OFF position associated with non-conduction and a de-energized state and the handle 51 can engage a lock 151 such as a padlock to lock the unit 50.sub.2 in this state.

[0138] For units with the power disconnect assembly 500, a user can also open slide 132 to insert crank 134 to move one or more line contacts (not shown) of the unit. When slide 132 is moved laterally aside to permit access to actuating mechanism 131, door 50f is prevented from opening, thereby closing off access to components inside the unit 50.sub.1, 50.sub.2. Additionally, a user may desire to padlock 232 the slide 132 in the closed position (FIG. 14B), to further regulate who may operate actuating mechanism 131 and when.

[0139] When slide 132 is moved aside, an aperture 136 (FIG. 9) is exposed. Opening 36 accepts a crank 134. Additionally, when slide 132 is moved aside as shown, slide 132 may optionally extend over a portion of front panel 50f. Thus, in embodiments in which front panel 50f is a hinged door, moving slide 132 to expose aperture 136 will inhibit a user from opening front panel 50f. Accordingly, so long as an operator has a crank 134 inserted into aperture 136 aligned with the internal actuator 131, the operator cannot open the door of the unit 50.sub.1, 50.sub.2.

[0140] FIGS. 9 and 10 show an example unit 50.sub.1, 50.sub.2 with an operator handle 51 coupled to the disconnect switch 60 and a power disconnect assembly 500 with retractable/extendable power stabs 554. During the extension of the power disconnect assembly 500 with the stabs 554 an automatic latch 60 can be triggered to engage the compartment 110 into which unit 50.sub.1, 50.sub.2 has been installed. Also due to the extension of the power disconnect assembly 500, a rod 78 is pulled by a stab bracket 59 such that a cam 80 is rotated away from a microswitch 582. Microswitch 582 is thus actuated to permit control voltage from a control power contact 44 to a motor control component, such as a contactor or overload relay (not shown). It is appreciated, however, that the position sensor assembly using the microswitch 582, cam 80 and rod 78 can be provided in other manners.

[0141] Also shown in FIG. 10 a second microswitch 594 can be connected to activate and deactivate a disconnect switch 60 such as a circuit breaker. When stabs 546, 548, 550 reach the fully engaged position with bus bars 200, stab bracket 59 actuates microswitch 594. When actuated, microswitch 594 permits closure of the disconnect switch 60, completing the circuit between bus bars 200 and the line side of motor control components (not shown) in unit 50.sub.1, 50.sub.2. Otherwise, microswitch 594 can prevent closure of its disconnect switch 60, e.g., circuit breaker. The microswitch 594 of the first unit 51 can send a trip signal to the disconnect switch 60 of the second unit 50.sub.2 when the microswitch 594 permits closure of its disconnect switch to trip the disconnect switch 60 in the second unit 50.sub.2 (and vice versa). This can be the signal transmitted via conductor lead 502 (FIGS. 3A, 3B, 3C, 7B).

[0142] Control power stab 44 can be un-shielded and connected to a control power once a respective unit 50.sub.1, 50.sub.2 is installed into a motor control center. However, microswitch 582 is in an activated state, due to the pressure thereon by cam 80. When microswitch 582 is in the activated state, as shown, microswitch 582 is interrupting control power from contact 44. Thus, the motor control components (not shown) housed in the unit housing 50h cannot initially be operated. Cam 80 will be moved by rod 78 via advancement of stab bracket 59, deactivating microswitch 582 and thereby permitting the flow of control power to motor control components (not shown) of the unit. Cam 80 also acts to display a location status of the stabs 546, 548, 550 to an operator. Cam 80 can have a number of colors thereon which can be displayed through front door 50f of the unit via stab indicator 24 (FIG. 8).

[0143] In the embodiment shown in FIG. 10, a disconnect switch (e.g., circuit breaker) interlock 316 includes microswitch 594, which gates the operation of the disconnect switch 60. FIG. 10 shows microswitch 594 in a deactivated state, in which button 334 thereof is not depressed. Arm 330 of microswitch 594 is positioned to abut a ledge 332 of interlock 316. Thus, when disconnect switch interlock 316 moves, due to the motion of stab assembly 58, the arm 330 of microswitch 594 will pivot, depressing button 334. When button 334 is depressed, microswitch 594 will be activated and will electrically allow operation of the disconnect switch (FIGS. 4-6).

[0144] FIG. 9 also has height H, width W and depth D dimensions which may be provided in modular frame sizes of 1-12 as discussed above with respect to the bypass unit 10. In some embodiments, the bypass unit 10 has a height that is less than the height of the units 50.sub.1, 50.sub.2. The bypass unit 10 and the units 50.sub.1, 50.sub.2 can have common depth and width dimensions. In other embodiments, the units 50.sub.1, 50.sub.2 can have common depth and width dimensions and the bypass unit 10 can have a different depth and/or width dimension.

[0145] Also shown in FIG. 10 is a shutter arm 336, having a sloped end 338. As stab 546 is advanced, stab 546 will engage the sloped end 338 and slide past shutter arm 336, thereby shifting shutter arm 336 to the left, as depicted in FIG. 10. When shutter arm 336 is shifted, it will strike a tab 340 of a rod 76 extending in a front to back direction of the unit. When tab 340 is struck, rod 76 will rotate, changing the color showing on shutter indicator 26 through door 50f of a respective unit 50.sub.1, 50.sub.2.

[0146] The electrical distribution devices contemplated by embodiments of the invention can include electrical and mechanical interlocks. FIG. 11 lists example actions of the first (primary) unit 50.sub.1, the second (redundant) unit 50.sub.2, and the bypass unit 10 providing an electrical interlocking system based on defined conditions or states of the first and second units 50.sub.1, 50.sub.2.

[0147] FIG. 12 lists example mechanical locks that can be used to provide a mechanical interlocking system for an electrical distribution device 100 with the first (primary) unit 50.sub.1, the second (redundant) unit 50.sub.2, and the bypass unit 10. That is, when units 50.sub.1, 50.sub.2 comprising a power disconnect assembly 500 is used (FIGS. 4-6, 9, 10), when one unit is energized, the other unit can be padlocked via padlock 132 (FIG. 14B) to lock the unit that is not being used to power the load to lock the power disconnect assembly 500 with its stabs in a retracted state with the slide 32 (FIGS. 8, 9) misaligned from portal 36.

[0148] At the same time the bypass unit 10 can be padlocked or otherwise locked into a primary mode associated with powering the load through the first unit 50.sub.1 or the bypass mode associated with powering the load through the second unit 50.sub.2.

[0149] A third interlock may be used where a trapped-key interlock device 250 of a unit 50.sub.1, 50.sub.2 that allows a disconnect switch 51 (e.g., breaker) to be operated only when the key is turned to allow the handle 51 to be turned to the ON position (FIGS. 13A, 13B, 14A). As is known to those of skill in the art, a trapped-key interlock typically has a lock cylinder which operates a sliding bolt through a cam. The sliding bolt, when extended, mechanically prevents operation of a switch, valve, gate, or other device. Many variations exist, with different shapes of interlock bolt and multiple lock cylinders on an interlock. The key is held or trapped in one position of the lock; releasing the key indicates that the interlocked device has been made safe; the interlocked device cannot be re-energized until the key has been returned and operated to retract the bolt. An example of a trapped-key interlock device 250 is a Kirk key safety interlock from Kirk Key Interlock Company, North Canton, OH.

[0150] A first standard unit 50.sub.1 with a first motor starter (e.g., a VFD, Soft starter, NEMA starter, IEC starter or the like) can be referred to as unit A and a second standard unit 50.sub.2 as a redundant unit with a motor starter of the same or different type (e.g., a VFD, Soft starter, NEMA starter or IEC starter of the like) can be referred to as unit B and can be placed in an adjacent location next to unit A. A third (compact) unit C provided as the bypass unit 10 comprises the power transfer circuit 20 with a transfer switch 25 which controls the connection to the load 80, and which switches motor control from the unit A to unit B. Both unit A and unit B can comprise power disconnect assemblies 500 allowing for (FlashGard isolator features providing arc flash safety, e.g., a stab racking mechanism with bus isolation and stab position indicators) power bus isolated unit configurations. The disconnect switches 60 in the two units can be configured as main circuit breakers that can be mechanically interlocked with a mechanical lock such as a Kirk Key interlock and can also be electrically interlocked with shunts trip accessories controlled by position sensors such as microswitches and auxiliary switches and/or relays in those units 50.sub.1, 50.sub.2 associated with, for example, FlashGard isolators and interlocks. As each unit 50.sub.1, 50.sub.2 has a separate unit door 50f, each of these units can be electrically isolated and completely disconnected from the power bus 200, i.e., a 480V/600V system, providing a safe working environment.

[0151] The unit 10, 50.sub.1, 50.sub.2 can be configured for DC (direct current) and/or AC (alternating current) operation.

[0152] In some embodiments, the circuit breaker 29 and/or the disconnect switch 60 of the units 50.sub.1, 50.sub.2 can comprise a molded case circuit breaker. Molded case circuit breakers are well known to those of skill in the art, as exemplified by U.S. Pat. Nos. 4,503,408 and 5,910,760, the contents of which are incorporated herein by reference as if recited in full herein. In other embodiments, the disconnect switch 60 can comprise a fused disconnect switch to turn power on and off.

[0153] Exemplary fuses are FUSETRON 600V Class RK5 fuses (BU-SB13729) available from Cooper Bussmann Company, St. Louis, MO. However, the design is flexible and can accommodate other fuses including those in different classes.

[0154] FIG. 15 illustrates that the electrical distribution system 100, such as, for example, an MCC 100M, can be configured with a bypass unit 10 comprising a manual back-up bypass configuration that provides an additional bypass path P.sub.3 that can be engaged if the auto bypass switch 25 with the first and second contactors 26.sub.1, 26.sub.2 is not operating properly. The electrical distribution system 100 as discussed herein can include any or all of the features described herein (i.e., the auxiliary inputs, interlocks and control circuits). The manual bypass path P.sub.3 can be provided as an override system that once mechanically engaged by a user operated switch 130 (FIG. 16), typically with an operator handle 231 (FIG. 17) can lock out the automatic bypass switch 25 and provide the power to the load 80 from the second unit 50.sub.2, through path P.sub.3 to the load 80. The manually engageable alternate or back-up bypass electrical path P.sub.3 includes a circuit breaker 129 that is normally open so that the alternate back-up bypass electrical path P.sub.3 is isolated until the manual handle 231 (FIG. 17) closes the contacts of the circuit breaker 129 and electrically and/or mechanically locks out the power transfer switch 25 and primary path P.sub.1 and bypass path P.sub.2. The first unit 50.sub.1 will be electrically isolated when the second unit 50.sub.2 is powering the load 80 as discussed above.

[0155] The second and third paths P.sub.2, P.sub.3, can merge to the conductor 34 inside the bypass unit 10 and be configured to connect with the second unit 50.sub.2 along a common conductor length/segment.

[0156] FIG. 16, which is similar to FIG. 2A, illustrates the bypass unit 10 can have a front panel 10f with the operator handle 230, the automatic bypass control switch 15 and the manual back-up bypass switch 130.

[0157] The operator handle 230 and manual switch 130 with an operator handle 231 can be configured as rotary or up-down operating handles. The electronic control switch 15 can be a push-button or a rotary button, in some embodiments. However, the electronic control switch 15 can have other configurations.

[0158] FIG. 17 illustrates an example of the bypass unit 10 with the automatic bypass switch 25 and manual bypass switch 130 shown as comprising an operator mechanism handle 231 coupled to the circuit breaker 129 which is adjacent the operator handle 230 coupled to the circuit breaker 29 of the bypass path P.sub.1 coupled to the first contactor 261 of the power transfer circuit 25 and the first unit 50.sub.1 (FIG. 15).

[0159] FIG. 18 illustrates that the bypass unit 10 can comprise a walking beam 229 coupled to the first and second breakers 29, 129 which defines an interlock that allows only one of the first breaker 29 in the primary path P.sub.1 or the second breaker 129 of the bypass path P.sub.3 to close at any one time. Other mechanical and/or electrical interlocks may be used.

[0160] FIGS. 19A/19B illustrate example actions that can be carried out according to embodiments of the present invention. A bypass unit with a power transfer circuit is the power transfer circuit is provided. The power transfer switch comprises mechanically interlocked first and second contactors configured to electrically couple to a load and define first and second electrical paths where only one of the first and second contactors close at any one time. The bypass unit further comprises a circuit breaker in the bypass unit coupled to a load side of the power transfer switch and also coupled to the first electrical path to thereby inhibit feedback to an isolated unit. The circuit breaker has an externally accessible operator handle that faces a front of the bypass unit and is configured to allow a user to lock the handle in an off position associated with non-conduction in the first electrical path (block 800).

[0161] Automatically transferring power from a power bus to a load from the first unit to the second unit using mechanically interlocked contactors while automatically tripping the circuit breaker in the bypass unit to thereby allow power transfer from one unit to one other while electrically isolating the other from the load and the one unit (block 810).

[0162] When the first unit is powering the motor and has a failure, the first disconnect switch is turned off to prevent electrical conduction in the first unit and a trip signal is sent to the circuit breaker in the bypass unit to automatically isolate the first unit (block 820).

[0163] The first disconnect switch is locked in the off position and the circuit breaker in the bypass unit can also be locked in the off position (block 830).

[0164] The second disconnect switch is turned on to allow electrical conduction in the second unit. Power from the power bus, through the second unit and the power transfer circuit is provided to the load (block 840).

[0165] A user is allowed to slidably withdraw or otherwise access the first unit while the second unit is operative (electrically active), with the first unit electrically isolated from the bypass unit and the second unit to thereby allow safe repair, servicing or replacement of the first unit while powering the load through the second unit and providing electrical isolation from the power transfer circuit in the bypass unit and the second unit (block 850)

[0166] The method can include automatically detecting a power failure or malfunction of the first unit, and automatically sending a trip signal to the first disconnect switch and the circuit breaker in the bypass unit to isolate the first unit from the load and the second unit (block 802).

[0167] The bypass unit with the power transfer switch cooperates with the first and second disconnect switches to force a shunt trip coil to trip the first disconnect switch (primary breaker) in the first unit (e.g., opens the primary breaker) and trip the circuit breaker in the bypass unit itself (block 804).

[0168] The bypass unit and the first and second units have a common width and modular housings and are slidably mountable in compartments of a structure of an MCC, each unit with respective front doors that can be independently locked (block 808).

[0169] The bypass unit is in an enclosed housing having a rear wall and first, second and third conductors that extend out of the bypass unit, the first conductor (only) coupled to the first unit and the second conductor (only) coupled to the second unit to electrically couple the first and second units to the load via the bypass unit (block 806).

[0170] Extending retractable/extendable power stabs of a power disconnect assembly of the first unit to electrically engage the power bus while a front door of the first unit remains closed (block 812).

[0171] The first and second units comprise electrical and mechanical interlocks configured to allow only one of the first and second disconnect switches (e.g., circuit breakers) to be ON at any one time (block 814).

[0172] Retracting the retractable/extendable power stabs to disengage from the power bus while a front door of the first unit remains closed (block 822).

[0173] The bypass unit can have an external user switch input that accepts user input to close one of the first set or the second set of switch contacts of one of the contactors. When transferring power from the first unit to the second unit, the first set of switch contacts are opened and the second set of switch contacts are closed (block 824).

[0174] Extending retractable/extendable power stabs of a power disconnect assembly of the second unit to electrically engage the power bus while a front door of the second unit remains closed (block 842).

[0175] FIG. 20 is a flow chart of example actions of a modular build assembly allowing for standardized builds from defined sets of different units avoiding unique single build customization according to embodiments of the present invention.

[0176] A bypass unit is provided. The bypass unit comprising a power transfer switch with mechanically interlocked first and second contactors configured to electrically couple to a load and define first and second electrical paths where only one of the first and second contactors close at any one time, wherein the bypass unit further comprises a circuit breaker in the bypass unit coupled to a load side of the power transfer switch and also coupled to the first electrical path to thereby inhibit feedback to an isolated unit, wherein the circuit breaker has an externally accessible operator handle that faces a front of the bypass unit and is configured to allow a user to lock the handle in an off position associated with non-conduction in the first electrical path (block 900). Two units are selected to connect to the bypass unit from at least three different modular units, optionally two of the same or two different ones from the following at least three types (block 910).

[0177] A first unit comprising a variable frequency drive (block 912). A second unit comprising a NEMA starter (block 914), and a third unit comprising a soft starter (block 916).

[0178] The first, second and third units can each comprise a power disconnect assembly having extendable/retractable power stabs (block 920).

[0179] The bypass unit and the selected two units can be slidably inserted into compartments of a structure, such as a structure of an MCC and the power transfer switch of the bypass unit is electrically coupled to the selected two units during, before or after the inserting (block 925).

[0180] It is contemplated that both new builds and field retrofit structures of electrical distribution devices 100 such as MCCs 100M can benefit from the new bypass unit 10 and primary and secondary units 50.sub.1, 50.sub.2 discussed above.

[0181] FIG. 21 is a flow chart of actions that can be used to automatically transfer power to a load according embodiments of the present invention.

[0182] An electrical distribution system such as an MCC is provided. The MCC has a bypass unit in a housing comprising a power transfer switch configured to serially electrically couple to a single one of first and second units held in separate respective housings to a load at any one time to thereby provide a redundant, back-up drive capacity (block 950).

[0183] First and second contactors of the power transfer switch are mechanically interlocked to electrically couple either the first or the second contactor to the load at any one time and define first and second electrical paths whereby only one of the first and second contactors close at any one time, wherein the first electrical path is electrically coupled to a circuit breaker in the bypass unit and the first unit and the second electrical path is coupled to the second unit (block 960).

[0184] A power failure or malfunction of the first unit is electronically detected (typically using a relay system) (block 970).

[0185] If a malfunction of power failure is detected, then automatically transmitting a trip signal to the circuit breaker in the bypass unit, automatically engaging the second contactor and disengaging the first contactor of the power transfer switch to power the load using the second unit and the second electrical path; automatically tripping a disconnect switch in the first unit; and automatically tripping the circuit breaker in the bypass unit to thereby isolate the first unit from the load (blocks 975-979).

[0186] Optionally, the bypass unit can include a back-up bypass path with a circuit breaker and the methods can include allowing a user to manually engage the back-up bypass path while concurrently interlocking a circuit breaker of the first primary path from being in an operative position (block 981).

[0187] The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the invention.