Unico Corp.

Keith W Van Patten

William S Hammel

Ramdas M Pai

Donald B Lawson

A digital current regulator for controlling the operation of an inductance device such as an AC motor. A plurality of independently controllable insulated gate bipolar transistors are selectively enabled to vary the instantaneous phase and magnitude of current applied to an AC motor. To minimize induced back EMFs during current switching operations, a number of safeguards are utilized. Switching between adjacent states only is provided to minimize the magnitude of instantaneous current changes. A 'ready blocking' function limits the maximum switching frequency to avoid significantly derating the switching device capabilities, while a 'time out' feature assures system operation above at least a minimum switching frequency to further minimize the magnitude of instantaneous current changes. A time hysteresis function is provided to avoid switching device response to false feedback control signals.

Digital current regulator

A linear resolver utilizes multiple pairs of nulled coil sets arranged co-linearly for sensing the position of multiple edges of a magnetically permeable object. An excitation coil produces an alternating magnetic field which is normally weakly coupled to the nulled coil sets across a magnetic gap. As the object covers the area of the gap, the coupling between the excitation and the individual coils in a nulled coil set is increased. Each nulled coil set produces an output which varies cyclically with increasing coverage of the object. The two nulled coil sets in each pair of nulled coil sets are offset from each other so that their cyclical outputs are offset by one quarter cycle, or 90.degree. with respect to the area of coverage by the object. Detection means are provided which resolve the outputs from a pair of nulled coil sets to precisely determine the position of the object edge. Each nulled coil pair is processed separately by the detection means so that multiple edges can be detected.

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Racine, WI, United States of America

Keith W Van Patten