Kollmorgen Technologies Corporation

Kollmorgen Corporation

John V Byrne

Francis McMullin

Jeremiah B O'Dwyer

Aengus Murray

Michael Egan

John Murphy

Francis Devitt

Michael Brosnan

Patrick Kenneally

James Lawton

Jeremiah B O'dwyer

In a control system for a reluctance motor driving a load, the output of a reference waveform generator is applied to a power converter through a current controller. The output of the generator is determined by rotor position, as detected by a sensor. The generator establishes a relative magnitude for motor phase current for every position of the rotor during the period of energization of a motor phase. A further control input may determine the absolute magnitude of the motor phase current, subject to the waveform pattern established by the generator. The reference waveforms may be sinusoidal. A method of determining the configuration of suitable reference waveforms for a given motor involves monitoring selected parameters of motor operation while controlling other such parameter in a test procedure.

Control systems for variable reluctance electrical machines

In a sensor having a drive winding for establishing a forward field, an electrically conductive screen is displaceable relative to a sense winding. In the presence of the drive field, eddy currents are generated in the screen to establish a counter-field opposing the forward field, so that the sense winding is shaded by the screen to a varying extent during relative displacement of screen and sense winding and the voltage induced in the sense winding is accordingly correspondingly varied. Application of a high frequency input to the drive winding results in a modulated output from the sense winding which may be demodulated to provide a signal indicative of screen position relative to sense winding. The position signal may be further processed to provide a speed signal. The sensor may assume a multiplicity of linear or planar, rotational and axial or solenoidal configurations.

Position and speed sensors

In a power supply system for a variable reluctance motor, each phase winding of the motor is connectible across a pair of supply rails by first and second switch means located respectively between the first supply rail and the winding and between the winding and the second supply rail. The first switch means is a fast switch-off device such as a gate turn-off thyristor or a transistor, while the second switch means is a slow turn-off device, such as a thyristor suitable for application to a line-commutation situation. In a two-phase configuration, where the second switch means is a thyristor, force-commutation of the second switch means may be achieved by means of a suitable capacitor interconnection between the thyristors switching the respective phases.

Power supply systems for reluctance motors

In a two-phase salient pole variable reluctance motor in which the number of stator poles is four or a multiple of four, alternate stator poles carry windings of different phases and each stator pole has an elongated pole shoe, so that the pole tips of each adjacent pair of stator poles are closely spaced. Each rotor pole has an iron depletion layer in the vicinity of its poleface surface which defines a saturating zone, across which the greater part of the magnetomotive force produced by stator windings is developed by uniform flux build-up with rotor angle throughout almost the entire duration of pole overlap. A working stroke approximating a stator pole pitch is achieved. The circumferential extent of each rotor pole is matched to that of the stator poles so that when the rotor poles are fully aligned with a pair of stator poles, each rotor poletip is located in the vicinity of a pair of spaced apart stator pole tips, the relative disposition of the pole tips being such that when both phases of the motor are then simultaneously excited, fringing flux passes through the rotor poletips, this flux being relatively strong for one poletip of each rotor pole and relatively weak for the other poletip. When the rotor poles are initially positioned so that there is partial overlap between rotor and stator poles, the motor is started by a conventional reluctance motor phase sequence, but when the rotor poles are initially fully aligned with stator poles, in which position neither phase acting alone is capable of producing torque, both phases are excited simultaneously, so that torque is applied to the rotor by the flux asymmetry to move the rotor into normal phase energization. The motor is bi-directional and self-starting in both senses from any rotor position.

Electrical drive systems incorporating variable reluctance motors

In a power supply system, an inductance L is connected between a rail at a voltage V.sub.1 and a rail at earth through a switch S. When the switch is opened, a current i.sub.2 flowing from the inductance L is directed to a third rail through a diode D, voltage on the third rail rising to V.sub.2. The system may function as a dc to dc converter with an output voltage between the V.sub.1 rail and V.sub.2 rail equal to V.sub.2 -V.sub.1. The system may alternatively be used in, for example, a reluctance motor drive, in which case a further inductance with associated switch and diode is included in the circuit in inverse configuration to prevent excessive voltage rise on the third rail.

Power supply systems for inductive elements

A drive system includes a reluctance motor, driving a load. The motor has stator and rotor poles and magnetizing windings for each stator pole. The airgap is small so that saturation occurs during pole overlap, and the poles are constructed so that there is torque overlap between phases as successive phases are energized during rotor rotation. A sensor provides a rotor position input to a reference waveform generator. The output of the generator is determined by rotor position and is applied to a power converter through a current controller. Accordingly the waveform generator establishes a relative magnitude for motor phase current for every position of the rotor during the period of energization of a motor phase. A further input may be applied to the system to determine the absolute magnitude of the phase current, subject to the waveform pattern established by the generator. The rotor poles may be skewed to modify the static torque versus rotor angle characteristic of the motor, the skew being between one-quarter and one-half of rotor pole arcuate extent.

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Dalkey, Ireland

John V Byrne