SYSTEMS, APPARATUS, AND METHODS FOR ELECTRIC CIRCUIT BREAKER TRIPPING

Abstract

Embodiments provide systems, apparatus, and methods for circuit breaker tripping. Embodiments include providing a circuit breaker with a thermoelectric tripping mechanism, the thermoelectric tripping mechanism including a thermoelectric plate disposed between a current path and a bimetal lever of the circuit breaker; applying a DC current to the thermoelectric plate to heat the bimetal lever; and deflecting the bimetal lever to press upon a trip bar in response to a current overload occurring on the current path. Numerous additional aspects are disclosed.

Claims

1. A circuit breaker comprising: a current path including contacts openable to interrupt a circuit; a thermoelectric tripping mechanism adjacent the current path, the thermoelectric tripping mechanism including a thermoelectric plate disposed between the current path and a bimetal lever, wherein the thermoelectric tripping mechanism includes a support upon which the thermoelectric plate is mounted, wherein the support is used as a first heat sink by the thermoelectric plate, wherein the thermoelectric plate includes a cold side coupled to the current path and a hot side coupled to the bimetal lever, and wherein the cold side uses the current path as a second heat sink and the hot side heats the bimetal lever; and a trip bar disposed to be pressed by the bimetal lever, the trip bar coupled to a stored energy mechanism releasable to open the contacts

2. The circuit breaker of claim 1 wherein the thermoelectric tripping mechanism includes a DC power supply coupled to the thermoelectric plate.

3. The circuit breaker of claim 2 wherein the thermoelectric plate is operative to heat the bimetal lever and use the current path as a heat sink.

4. The circuit breaker of claim 2 wherein the DC power supply includes a current transformer coupled to the current path.

5. The circuit breaker of claim 4 wherein the DC power supply further includes a rectifier coupled to the current transformer and the thermoelectric plate.

6. (canceled)

7. (canceled)

8. A thermoelectric tripping mechanism comprising: a current path; a bimetal lever; a support; and a thermoelectric plate disposed between the current path and the bimetal lever, wherein the support upon which the thermoelectric plate is mounted, wherein the support is used as a first heat sink by the thermoelectric plate, wherein the thermoelectric plate includes a cold side coupled to the current path and a hot side coupled to the bimetal lever, and wherein the cold side uses the current path as a second heat sink and the hot side heats the bimetal lever.

9. The thermoelectric tripping mechanism of claim 8 further including a DC power supply coupled to the thermoelectric plate.

10. The thermoelectric tripping mechanism of claim 9 wherein the thermoelectric plate is operative to heat the bimetal lever.

11. The thermoelectric tripping mechanism of claim 9 wherein the DC power supply includes a current transformer coupled to the current path.

12. The thermoelectric tripping mechanism of claim 11 wherein the DC power supply further includes a rectifier coupled to the current transformer and the thermoelectric plate.

13.-20. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is an isometric view diagram depicting a thermomagnetic tripping mechanism according to the prior art.

[0012] FIG. 2 is a side view diagram depicting a thermomagnetic tripping mechanism according to the prior art.

[0013] FIG. 3 is an isometric view diagram depicting an example thermomagnetic circuit breaker according to some embodiments.

[0014] FIG. 4 is a side view diagram depicting an example thermomagnetic circuit breaker according to some embodiments.

[0015] FIG. 5 is an isometric view diagram depicting an example thermoelectric tripping mechanism according to some embodiments.

[0016] FIG. 6 is a side view diagram depicting an example thermoelectric tripping mechanism according to some embodiments.

[0017] FIG. 7 is a front view diagram depicting an example thermoelectric tripping mechanism according to some embodiments.

[0018] FIG. 8 is a back view diagram depicting an example thermoelectric tripping mechanism according to some embodiments.

[0019] FIG. 9 is a top view diagram depicting an example thermoelectric tripping mechanism according to some embodiments.

[0020] FIG. 10 is an exploded isometric view diagram depicting an example thermoelectric tripping mechanism according to some embodiments.

[0021] FIG. 11 is a circuit diagram depicting a first example circuit for wiring a thermoelectric tripping mechanism according to some embodiments.

[0022] FIG. 12 is a circuit diagram depicting a second example circuit for wiring a thermoelectric tripping mechanism according to some embodiments.

[0023] FIG. 13 is a circuit diagram depicting a third example circuit for wiring a thermoelectric tripping mechanism according to some embodiments.

[0024] FIG. 14 is a flowchart illustrating an example method according to some embodiments.

DETAILED DESCRIPTION

[0025] Embodiments disclosed herein describe a thermoelectric tripping mechanism for use in a thermomagnetic circuit breaker. As discussed above, thermomagnetic circuit breakers use a bi-metallic or tri-metallic element to sense temperature on the current path and use the deflection of the bimetal lever to activate the tripping mechanism in case of an overload. To achieve sufficient deflection with adequate pushing force, the bimetal lever is conventional coupled to a heater element for indirect heating or is connected as part of the current path for direct heating. However, the heat generated from heating the bimetal is transferred to the rest of the current path, mainly by conduction and convection. As a result, the temperature of the entire circuit breaker is increased. The increased temperature can damage the lugs and cables connected to the circuit breaker, or may cause a generalized overheating condition of the surroundings of the circuit breaker.

[0026] Conventionally, in order to limit the maximum temperature of the circuit breaker during normal operation, the size of the elements in the current path, where the heater of the bimetal is located, are increased to provide more heat dissipation. In addition, more expensive materials with very good thermal or electrical conductivity are used to further help dissipate the heat. Thus, conventional thermomagnetic circuit breakers are forced to balance competing aspects: on one hand, increasing heat to achieve sufficient deflection with adequate pushing force with the bimetal lever and, on the other hand, limiting heat to prevent damage to the circuit breaker and surrounding elements. Achieving this balance has conventionally been accomplished at the expense of using larger components and more expensive materials.

[0027] The thermomagnetic circuit breakers of embodiments disclosed herein avoid the competing aspects of conventional circuit breakers. Instead, embodiments use a thermoelectric plate to heat the bimetal lever without providing extra heat to the current path. A thermoelectric plate works based on the principal of the Peltier effect. Due to the Peltier effect, a thermoelectric plate creates voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, it creates a temperature difference. At the atomic scale, an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side. This effect can be used to generate electricity, measure temperature or, in the case of embodiments disclosed herein, change the temperature of objects such as the bimetal lever. Because the direction of heating and cooling is determined by the polarity of the applied voltage, thermoelectric plates can be used as temperature controllers. The cold side of the thermoelectric plate is attached to the current path to use the current path as a heat sink. The bimetal lever is attached to the hot side to aid in deflection.

[0028] In some embodiments, a DC current is applied to the thermoelectric plate to induce the temperature gradient between the two sides. The DC current can be generated from the current path using a current transformer and a rectifier diode. The heat produced by the thermoelectric plate, is only applied to the bimetal lever without heating the entire current path. Therefore, the material cost of the current path can be reduced and the entire size of the circuit breaker can also be reduced. Circuit breakers that operate at lower temperatures than conventional breakers allow optimization the panel board design upon which they are mounted. For example, with reduced size breakers, more breakers can be included within a smaller panel. Further, by controlling the DC current applied to the thermoelectric plate so that it only flows above a predefined value, the thermal calibration process of the circuit breaker can be eliminated or greatly simplified.

[0029] Turning now to FIGS. 3 and 4, an example of a thermomagnetic circuit breaker 300 with a thermoelectric tripping mechanism 302 is depicted. The thermoelectric tripping mechanism 302 includes a support 304 upon which a thermoelectric plate 306 is mounted and a bimetal lever 308 is coupled to the thermoelectric plate 306 via retaining clamp 310. A trip bar 312 is disposed proximate to the bimetal lever 308. The trip bar 312 is linked to a latch 314 that retains a spring within housing 316. (The spring within housing 316 is not visible in the drawings.) The spring provides tension to maintain a contact (also within the housing and thus not visible in the drawings) pressed against load plate 318.

[0030] FIGS. 5 through 10 provide detailed views of the thermoelectric tripping mechanism 302. FIG. 5 is an isometric view and FIG. 6 is a side view of the thermoelectric tripping mechanism 302. FIGS. 7, 8 and 9 are front, back, and top views respectively of the thermoelectric tripping mechanism 302. FIG. 10 is an exploded isometric view.

[0031] Referring to FIGS. 3 through 10, in operation, the thermoelectric plate 306 provides heat to the bimetal lever 308 when an overload condition exists. The bimetal lever 308 deflects in response to the heat and presses against the trip bar 312 which in turn disengages the latch 314. Releasing the latch 314 frees the spring to open the current path by disengaging the contact from the load plate 318.

[0032] Notably, support 304 is used as a heat sink by the thermoelectric plate 306 and thus, a narrowed section which creates the conventional heater is not needed. Therefore, the overall width of support 304 can be significantly smaller than the widest portion of the structure conventionally used for supporting the bimetal lever. For example, whereas a conventional structure for a 600A breaker may be formed from approximately 0.091 inch thick material with a reduced cross section from approximately 1.5 in its widest area to approximately 0.96 in the narrowest area (for heating effects) and a length of approximately 5 inches, the support 304 of present embodiments can be reduced to being only approximately 4 inches long and approximately 1.2 wide for an overall reduction of material of approximately 20%.

[0033] Turning now to FIG. 11, a schematic diagram of an example circuit 1100 for a thermoelectric tripping mechanism 302 is provided. In the example circuit 1100 shown, input line 1102 carries AC line current, as indicated by graph 1104, to current transformer 1106 and along the current path 1120. Current transformer 1106 outputs a stepped down AC current (e.g., lower power) on line 1108, as indicated by graph 1110, which flows to the input of rectifier 1112. Rectifier 1112 outputs a DC current on line 1114, as indicated by graph 1116, which flows to the thermoelectric plate 1118. The cool side of the thermoelectric plate 1118 is coupled to and uses the current path 1120 as a heat sink. The hot side of the thermoelectric plate 1118 is coupled to and heats the bimetal lever 1122. When a current overload occurs on the current path 1120, the bimetal lever 1122 deflects due to the additional heat generated by the increased current supplied to the thermoelectric plate 1118. The deflected bimetal lever 1122 presses upon the trip bar 1124 to release the stored energy spring 1126 which opens contacts 1128 to interrupt the circuit.

[0034] In some embodiments, the DC current applied to the thermoelectric plate 1218 can be controlled so that current only flows to it above a predefined value as illustrated in FIG. 12. Gating the signal to the thermoelectric plate 1218 eliminates or greatly simplifies the thermal calibration process of the circuit breaker. FIG. 12 depicts a schematic diagram of a second example circuit 1200 for a thermoelectric tripping mechanism 302. In the second example circuit 1200 shown, input line 1202 carries AC line current, as indicated by graph 1204, to current transformer 1206 and along the current path 1220. Current transformer 1206 outputs a stepped down AC current (e.g., lower power) on line 1208, as indicated by graph 1210, which flows to the input of rectifier 1212. Rectifier 1212 outputs a DC current on line 1214, as indicated by graph 1216, which flows to voltage comparator 1230. Voltage comparator 1230 also receives a reference voltage (not shown) that is used to calibrate the second example circuit 1200.

[0035] If the voltage of the DC current from the rectifier 1212 is less than the reference voltage, the voltage comparator 1230 does not output any current on line 1232 as indicated in the OFF portion of graph 1234. If however, the voltage of the DC current from the rectifier 1212 is greater than the reference voltage, the voltage comparator 1230 does output a current on line 1232 as indicated in the ON portion of graph 1234.

[0036] The cool side of the thermoelectric plate 1218 is coupled to the bimetal lever 1222. The hot side of the thermoelectric plate 1218 is coupled to the current path 1220. When a current overload occurs on the current path 1220, the voltage of the DC current from the rectifier 1212 exceeds the reference voltage, a current is applied to line 1232, and the thermoelectric plate 1218 is energized to heat the bimetal lever 1222 and to use the current path 1220 as a heat sink. The heated bimetal lever 1222 deflects due to the heat from the thermoelectric plate 1218 and the deflected bimetal lever 1222 presses upon the trip bar 1224 to release the stored energy spring 1226 which opens contacts 1228 to interrupt the circuit.

[0037] Therefore, a benefit of the embodiment of FIG. 12 is that the precise position and amount of physical deflection of the bimetal lever 1222 in response to heat from the thermoelectric plate 1218 (driven by current from the current path 1220) does not need to be accurately calibrated. In other words, since the bimetal lever 1222 is not heated at all during normal operation and only heated when an overload condition exists, the bimetal lever 1222 can be disposed immediately adjacent the trip bar 1224 and any deflection of the bimetal lever 1222 can be used to trigger the trip bar 1224. The reference voltage supplied to the voltage comparator 1230 is used to determine how much current on the current path should cause the breaker to be tripped by gating the DC current supplied to the thermoelectric plate 1218 until the current on the current path 1220 exceeds an overload condition threshold. Thus, instead of having to precisely configure the position and physical response of the bimetal lever 1222, the voltage comparator 1230 allows binary operation of the thermoelectric plate 1218. A further benefit is that since the bimetal lever 1222 is only heated when an overload condition occurs, energy consumption is reduced.

[0038] FIG. 13 depicts a third example circuit 1300 for a thermoelectric tripping mechanism 302. The third example circuit 1300 provides improved reliability and safety features. In the third example circuit 1300 shown, input line 1302 carries AC line current, as indicated by graph 1304, to current transformer 1306 and along the current path 1320. Current transformer 1306 outputs a stepped down AC current (e.g., lower power) on line 1308, as indicated by graph 1310, which flows to the input of rectifier 1312. Rectifier 1312 outputs a DC current on line 1314, as indicated by graph 1316, which flows to voltage comparator 1330. Voltage comparator 1330 also receives a reference voltage (not shown) that is used to calibrate the third example circuit 1300.

[0039] In normal operation, voltage comparator 1330 applies a current on line 1332 that flows to the thermoelectric plate 1318 as shown in the ON portion of graph 1334. The thermoelectric plate 1318 is disposed with the cool side against the bimetal lever 1322 and the hot side against the current path 1320. Thus, in normal operation, the bimetal lever 1322 is held in a deflected position without pressing on the trip bar 1324. In a current overload condition, the voltage comparator 1330 cuts off the current on line 1332 and flow to the thermoelectric plate 1318 is stopped as shown in the OFF portion of graph 1334. The bimetal lever 1322 is no longer cooled and thus, returns to a non-deflected position which presses on the trip bar 1324 to release the stored energy spring 1326 which opens contacts 1328 to interrupt the circuit.

[0040] Therefore, in addition to the reduced configuration benefit of binary operation due to the use of a voltage comparator 1330, a safety and reliability benefit of the embodiment of FIG. 13 is that even if a component fails and no longer conducts, the circuit breaker will be interrupted since without power, the third example circuit 1300 defaults to a tripped state.

[0041] Note that throughout the present specification, the term bimetal lever is used to refer to the temperature responsive structure that deflects due to different coefficients of thermal expansion of the materials used to form the lever. In some embodiments, three, four, or more materials can be used to form a temperature responsive lever. Thus, the term bimetal is only used for clarity and convenience and one of ordinary skill will understand that multiple materials (including non-metal) can be used together to form a temperature responsive lever.

[0042] Further, in some embodiments, the current path is used as a heat sink for the bimetal lever. However, a heat sink is not required in some embodiments and alternatively, a separate heat sink can be used. In some embodiments, a transceiver (e.g., a wired or wireless transceiver) can be coupled to the voltage comparator to adjust the reference voltage. Thus, a remote signal can be transmitted to the voltage comparator to cause the circuit breaker to trip. Likewise, in some embodiments, the transceiver can be connected to the output of the voltage comparator to send a signal when the thermoelectric plate is being energized or not, or if there is a change in the signal to the thermoelectric plate, indicating the occurrence of an overload condition and/or a current status of the circuit breaker.

[0043] Turning now to FIG. 14, a flow chart 1400 depicting an example method of tripping a circuit breaker is described. A circuit breaker including a thermoelectric tripping mechanism is provided (1402). The thermoelectric tripping mechanism includes a thermoelectric plate with a cold side coupled to the current path of the circuit breaker and the hot side coupled to a bimetal lever of the breaker. A DC current is applied to the thermoelectric plate with a magnitude based on the amount of current flowing on the current path (1404). The thermoelectric plate heats the bimetal lever in proportion to the amount of current flowing on the current path and uses the current path as a heat sink (1406). When a current overload occurs on the current path, the bimetal lever is further heated and deflects due to the increased energy on the current path (1408). The deflected bimetal lever presses upon the trip bar to release the stored energy spring which opens contacts to interrupt the circuit (1410).

[0044] Numerous embodiments are described in this disclosure, and are presented for illustrative purposes only. The described embodiments are not, and are not intended to be, limiting in any sense. The presently disclosed embodiments are widely applicable to numerous other embodiments, as is readily apparent from the disclosure. One of ordinary skill in the art will recognize that the disclosed embodiments may be practiced with various modifications and alterations, such as structural, logical, software, and electrical modifications. Although particular features of the disclosed embodiments may be described with reference to one or more particular embodiments and/or drawings, it should be understood that such features are not limited to usage in the one or more particular embodiments or drawings with reference to which they are described, unless expressly specified otherwise.

[0045] The present disclosure is neither a literal description of all embodiments nor a listing of features of the embodiments that must be present in all embodiments. The present disclosure provides, to one of ordinary skill in the art, an enabling description of several embodiments. Some of these embodiments may not be claimed in the present application, but may nevertheless be claimed in one or more continuing applications that claim the benefit of priority of the present application.

[0046] The foregoing description discloses only example embodiments. Modifications of the above-disclosed apparatus, systems. and methods which fall within the scope of the claims will be readily apparent to those of ordinary skill in the art. Accordingly, while the embodiments have been disclosed in connection with example embodiments thereof, it should be understood that other embodiments may fall within the intended scope, as defined by the following claims.