National Research Development Corporation

Switched Reluctance Drives Limited

Austin Hughes

Peter John Lawrenson

John M Stephenson

Raymond Mann

A controller for an electronically commutated electrical machine receives a feedback signal indicative of a parameter which it is desired to minimize, e.g. torque ripple, current, voltage, vibration or acoustic noise. The controller computes the amplitude and phase of a set of harmonics in the parameter and sequentially injects harmonics of the correct amplitude and phase to minimize the parameter. An optimizing routine iterates through the set of harmonics to further reduce the parameter.

Apparatus and method for controlling an electric machine

An electric stepper motor has in addition to the usual driving coils at least one additional coil wound on its stator and connected in a closed circuit. This additional coil damps any oscillations of the rotor. The closed circuit has a resistive value optimized to achieve maximum damping effect. Two or more such additional coils may be connected in a single closed circuit and a number of such closed circuits may be provided.

Electric stepper motors

A stepper motor has impedance in series with each drive coil and the value of the impedance is changed during each drive pulse. Two different paths for current to a drive coil may be provided each having a different value of impedance and the current to the drive coil is switched between the two paths during each drive period.

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Leeds, United Kingdom

Austin Hughes