A control system for and method of controlling a switched reluctance generator to maintain stable control of the generator in the continuous current mode. This is achieved by sensing the load on the generator, the speed of the rotor and the position of the rotor with respect to each phase winding in order to derive switching command signals to maintain the volt-seconds applied to the winding in each phase period so as to inhibit progressive flux growth in the phase windings by actuation of the controller switches.

Control of switched reluctance machines

A method and apparatus for operating a polyphase dc motor selectively in dual-coil or uni-coil commutation modes. The motor has a plurality of "Y" connected driving coils connected together at a center tap. Each driving coil has an input node at an end opposite the center tap, and is driven by a switch pair. Each switch pair is arranged for connection in series across a power supply voltage, and has a node between each switch connected to a respective one of the coil input nodes. An additional pair of switches are provided for connection in series across the power supply with a connection node between each switch connected to the center tap. A circuit is provided to operate the switches to cause a driving current to be passed between sequentially selected pairs of the driving coils for an initial start-up time. Also, a circuit to operate the switches after the initial start-up time is provided to cause a driving current to be passed between sequentially selected only single ones of the driving coils and the center tap current input node. The apparatus also has a circuit for detecting a zero crossing of a bemf signal of a floating one of the driving coils and a delay circuit for establishing a delay between a zero crossing and a commutation of driving signals to the coils. A circuit operates the delay circuit to provide a first predetermined delay in dual-coil mode and a second predetermined delay in uni-coil mode.

Method and apparatus for starting a sensorless polyphase DC motor in dual-coil mode and switching to single coil mode at speed

A permanent magnet synchronous motor system. The system uses a permanent magnet AC synchronous motor having an elongated housing, of the type used in progressive cavity pumping applications. Within the stator, a multi-section rotor is rotatably mounted. The rotor includes a plurality of rotor sections that are angularly offset from each other. The rotor sections are mounted on a drive shaft, and the sum of the offsets is generally comparable to the angular displacement undergone by the drive shaft under a normal operating load.

Elongated permanent magnet synchronous motor

A power conversion system for driving a three phase synchronous or induction motor receives power from AC power lines and rectifies the power to provide DC current on DC link lines through a link inductor. An inverter connected to the DC link lines is composed of three sets of two thyristors connected in series across the DC link lines. Three output lines extend from connections between each of the three sets of thyristors to the motor. Capacitors are connected across each of the three phase output lines. A controller controls the switching of the thyristors in two modes. In a first mode, used from start-up to low speed operation, a high frequency switching cycle is produced in three steps during which pairs of thyristors in different ones of the three sets are triggered. The relative length of time spent in each one of the three periods during the switching cycle is varied to obtain a desired change in the average output voltage on the three phase output lines at a fundamental frequency. The first mode provides power to drive the motor between standstill and an intermediate speed, with the phase voltages being controlled so that commutation of the thyristors is obtained during each switching cycle. While operating at any speed in the first mode, the system can transfer to a second mode having a four step switching cycle to generate a fundamental voltage component on the three phase output lines by changing the switching cycle in a six step sequence. The motor can be driven in the second mode to a desired speed, while control of the torque is obtained.

Thyristor based DC link current source power conversion system for motor driven operation

A brushless electric motor is disclosed. In an exemplary embodiment of the invention, the motor includes a permanent magnet rotor having a plurality of magnetic poles thereupon and a stator. The stator further includes a plurality of stacked laminations defining a plurality of slots therein, and a plurality of fractional-pitch phase windings disposed within the plurality of slots. The motor has a non-integer slots-per-pole ratio, and a magnitude of 5 th and 7 th harmonic components of a fundamental frequency component of the motor are less than 0.3% and 0.1% of a magnitude of the fundamental frequency component, respectively.

Fractional-slot winding motor

An electric induction motor/control system that provides the desirable high starting torque and wide speed characteristics of direct current motors. The stator of the induction motor has two specially interrelated winding sets per phase. The motor windings are supplied with unidirectional current pulses from silicon controlled rectifiers that are programmed to provide advantageous modes of operation for the motor. The unique relation and interaction between the motor windings hereof and the associated electronic circuitry results in high power factor, good efficiency, and self-clearing SCR commutation action. The preferred motors use a squirrel cage rotor with no commutator, brushes, or slip rings. The complementary stator winding arrangements are not voltage limited, and thereby permit the construction of large power motor systems. Practical motor ratings are from fractional to over 500 horsepower, at speeds ranging from 600 to 40,000 rpm, and higher. The electronic control sections for even the high horsepower motors are operated at low voltage and with few watts. Control circuitry is provided that can operate the motor systems: (a) at constant output torque over a wide speed range; (b) at constant horsepower over a selected speed range; (c) with traction output characteristics similar to that of series motors; (d) at constant speed; (e) and with direct speed reversal in any of these modes. These motor systems require little maintenance, and may be hermetically sealed.

J Greenwell

Papers

Induction motor system with constant torque