An adjustable speed drive (ASD) circuit includes a rectifier bridge to convert an AC power input to a DC power, a DC link coupled to the rectifier bridge to receive the DC power, a DC link capacitor bank comprising at least first and second capacitors connected to the DC link, each capacitor having a capacitor voltage thereacross, and a protection circuit including a detection circuit configured to detect a short circuit on one or more of the first and second capacitors of the DC link capacitor bank and generate an action signal upon detection of a short circuit on one or more of the first and second capacitors of the DC link capacitor bank. The ASD circuit also includes an action circuit in operable communication with the detection circuit and configured to cause a short circuit across the DC link upon receiving the action signal from the detection circuit.

This invention aims at developing an Induction Motor that consumes less power than existing Induction Motors. An efficient Induction motor comprises a stator that includes three field windings and a rotor that includes rotor conductors short-circuited at both ends by end rings located at both ends of rotor. A field winding comprises a number of pairs of North pole and South pole. There are three full-wave rectifiers. Each of the three full-wave rectifiers converts a phase current of a three phase alternating current supply into a unidirectional current varying with time and delivers the converted current exclusively to a field winding. As a result, poles of the field winding generate fluctuating magnetic flux. A rotor conductor cuts said fluctuating magnetic flux thereby inducing an emf in said rotor conductor and consequently generating current in it. The direction of said magnetic flux and the direction of said current flowing in said rotor conductor are perpendicular to each other. Said rotor conductor moves in a direction perpendicular to both the direction of said magnetic flux and said rotor conductor current thereby rotates the rotor.

This invention aims at developing an Induction Motor that consumes less power than existing Induction Motors. An efficient Induction motor comprises a stator that includes three field windings and a rotor that includes rotor conductors short-circuited at both ends by end rings located at both ends of rotor. A field winding comprises a number of pairs of North pole and South pole. There are three full-wave rectifiers. Each of the three full-wave rectifiers converts a phase current of a three phase alternating current supply into a unidirectional current varying with time and delivers the converted current exclusively to a field winding. As a result, poles of the field winding generate fluctuating magnetic flux. A rotor conductor cuts said fluctuating magnetic flux thereby inducing an emf in said rotor conductor and consequently generating current in it. The direction of said magnetic flux and the direction of said current flowing in said rotor conductor are perpendicular to each other. Said rotor conductor moves in a direction perpendicular to both the direction of said magnetic flux and said rotor conductor current thereby rotates the rotor.

The present invention belongs to the technical field of alternating current induction servo motors, and particularly relates to a rotary-type induction servo motor with a constant-output-torque by using uniform magnetic fields and a linear-type induction servo motor with a constant-output-force by using uniform magnetic fields. The present invention has main features that the rotary-type induction servo motor or the linear-type induction servo motor is composed of N independent motor units; each independent motor unit has the same or similar structure, and is powered by single-phase alternating current; and the N independent motor units have an equal voltage magnitude of power supply, but voltage phases are different and form an arithmetic progression. In an independent motor unit of the rotary-type induction servo motor with a constant-output-torque by using uniform magnetic fields, the stator magnetic conductive silicon steel is simple in structure, and the winding manner of stator excitation windings is simple, similar to a multilayer solenoid type; rotor induction excitation windings are powered through induction, and no slip ring and related wearing parts are used. The rotary-type induction servo motor disclosed here can be operated at fixed voltage frequency, and in this case, the output torque and the voltage magnitude of power supply are in direct proportion, so the output torque can be controlled by adjusting the voltage magnitude. The motor does not adopt permanent magnetic materials, and has many merits including simple structure, good torque characteristic, simple controller design and high control precision. And meanwhile, based on the same principle, a linear-type induction servo motor with a constant-output-force by using uniform magnetic fields can be evolved from the rotary-type induction servo motor.

The present invention belongs to the technical field of alternating current induction servo motors, and particularly relates to a rotary-type induction servo motor with a constant-output-torque by using uniform magnetic fields and a linear-type induction servo motor with a constant-output-force by using uniform magnetic fields. The present invention has main features that the rotary-type induction servo motor or the linear-type induction servo motor is composed of N independent motor units; each independent motor unit has the same or similar structure, and is powered by single-phase alternating current; and the N independent motor units have an equal voltage magnitude of power supply, but voltage phases are different and form an arithmetic progression. In an independent motor unit of the rotary-type induction servo motor with a constant-output-torque by using uniform magnetic fields, the stator magnetic conductive silicon steel is simple in structure, and the winding manner of stator excitation windings is simple, similar to a multilayer solenoid type; rotor induction excitation windings are powered through induction, and no slip ring and related wearing parts are used. The rotary-type induction servo motor disclosed here can be operated at fixed voltage frequency, and in this case, the output torque and the voltage magnitude of power supply are in direct proportion, so the output torque can be controlled by adjusting the voltage magnitude. The motor does not adopt permanent magnetic materials, and has many merits including simple structure, good torque characteristic, simple controller design and high control precision. And meanwhile, based on the same principle, a linear-type induction servo motor with a constant-output-force by using uniform magnetic fields can be evolved from the rotary-type induction servo motor.

A motor includes a shaft presenting a shaft lead end, a switch assembly including a switch arm shiftable between a first position and a second position, and shield structure. The shaft lead end and the switch assembly are disposed axially outward of an endshield. The shield structure is disposed axially outward of the switch arm to at least substantially restrict direct tool access to the switch arm from an axially outward position relative to the switch arm. The shield structure at least in part defines first and second tool access channels each extending radially inwardly to the shaft lead end, such that the shield structure enables direct tool access to the shaft lead end via the tool access channels but prevents or at least substantially restricts direct tool access to the switch arm via the tool access channels.

In induction motors, efficiency is improved and a maximum torque is increased. For a magnetic flux density of the stator pole for each phase of an induction motor, a circumferential magnetic flux density distribution is controlled to any distribution state, from a trapezoidal wave-like distribution close to a square wave to a sinusoidal distribution. In particular, motor efficiency in a range of low to medium rotations is improved. The motor structure is designed to reduce the leakage inductance of the rotor windings, and the motor and control thereof are optimized for each other. This increases the maximum torque of the motor more effectively. In addition, the high efficiency of the motor makes it possible to reduce the size of the drive circuit.

An adjustable speed drive (ASD) circuit includes a rectifier bridge to convert an AC power input to a DC power, a DC link coupled to the rectifier bridge to receive the DC power, a DC link capacitor bank comprising at least first and second capacitors connected to the DC link, each capacitor having a capacitor voltage thereacross, and a protection circuit including a detection circuit configured to detect a short circuit on one or more of the first and second capacitors of the DC link capacitor bank and generate an action signal upon detection of a short circuit on one or more of the first and second capacitors of the DC link capacitor bank. The ASD circuit also includes an action circuit in operable communication with the detection circuit and configured to cause a short circuit across the DC link upon receiving the action signal from the detection circuit.

An adjustable speed drive (ASD) circuit includes a rectifier bridge to convert an AC power input to a DC power, a DC link coupled to the rectifier bridge to receive the DC power, a DC link capacitor bank comprising at least first and second capacitors connected to the DC link, each capacitor having a capacitor voltage thereacross, and a protection circuit including a detection circuit configured to detect a short circuit on one or more of the first and second capacitors of the DC link capacitor bank and generate an action signal upon detection of a short circuit on one or more of the first and second capacitors of the DC link capacitor bank. The ASD circuit also includes an action circuit in operable communication with the detection circuit and configured to cause a short circuit across the DC link upon receiving the action signal from the detection circuit.

A rotor of an induction motor includes a shaft, a ferromagnetic rotor core, first and second inductors axially bracketing the rotor core, and a rotor cage. The shaft extends along a stator axis, and the rotor core is disposed coaxially about the shaft. The rotor cage comprises first and second supports, and a plurality of cage bars. The supports are disposed axially between the rotor core and the first and second inductors, respectively. The cage bars surround the shaft, pass through the rotor core, are secured at the first and second supports, and are each electrically connected to both the first and second inductors.