Commutator for switched reluctance drive

A microprocessor based digital controller for selectively controlling the firing of stator phases in synchronism with rotor angular position of a multiphase switched reluctance drive over a wide speed range, comprising:

• microprocessor means for providing an advance angle signal representative of a desired shift in turn-on angle position of a sequence of stator phase firing pulses of common pulsewidth, a dwell angle signal indicative of a desired pulsewidth for said firing pulses, and a set current signal;
• commutation means for receiving and processing said advance angle signal, said dwell angle signal and a rotor angular position signal representative of instantaneous rotor angle position, and producing phase firing command pulses for each of said stator phases, said commutation means comprising Read Only Memory means for storing different sequences of said firing pulses, each sequence being stored as at least one digital word at each of a plurality of addressable locations of the memory means, each of said words corresponding to the switch state of all said stator phases for a particular rotor angular position, respectively, and each of said addressable locations corresponding to a different rotor position, respectively, over an electrical cycle of the drive, each of said different sequences corresponding to a difference in pulsewidth of the firing pulses, respectively, said commutator means further comprising summing means for summing said advance angle signal and rotor position signal to provide an address signal for addressing said Read Only Memory in synchronism with instantaneous rotor position, said commutator means further comprising dwell means for selecting which of said firing sequences is to be addressed by said address signal in accordance with the dwell signal received from the microprocessor means;
• and
• current regulated inverter means for receiving the set current signal from the microprocessor means and the phase switching command pulses from the commutator means and providing therefrom a stator phase firing pulse train for each stator phase.

A digital commutation method for providing firing pulses of adjustable firing angle to an inverter of a multiphase switched reluctance drive to selectively switch current on and off in stator phases of said drive in synchronism with rotor position, comprising the steps of:

• storing at least one standard multiphase firing pattern in a nonvolatile memory such that binary representations of a firing state of each stator phase for successive rotor angles over an electrical cycle of the drive are stored at successive addressable locations, respectively, in the memory;
• providing a first digital representaion of instantaneous rotor angular position;
• providing a second digital representaion of a desired advance angle, said advance angle representing a desired shift in location of said firing pattern with respect to rotor angle;
• adding said first and second digital representations to provide a composite address signal;
• and
• addresssing said memory with said address signal in synchronism with said digital representation of instantaneous rotor angular position so that the firing pattern shifted by said advance angle can be read out of said memory means.

In a multiphase switched reluctance drive, a method for controlling the switching of phases with phase firing pulses in a manner to allow variation in timing of the switching with respect to rotor position, comprising the steps of:

• storing information defining a first firing pattern of stator phase firing pulses over an electrical cycle of the drive as a function of rotor position in a digital nonvolatile memory, each pulse of said pattern being of identical duration and having a turn-on angle corresponding, respectively, to a different initial rotor position;
• receiving a binary position signal representative of instantaneous rotor angular position;
• modifying said position signal to provide a modified position signal adjusted to acheive a desired displacement of said pulses relative to their initial rotor positions;
• and
• employing the modified position signal to address and read out information from the memory in synchronism with instantaneous rotor angular position, whereby placement of said firing pulses and, accordingly, timing of said switching, can be adjusted as desired.