Abstract: Methods and apparatus are disclosed for relieving stresses related to reverse recovery of free-wheeling diodes of power inverter circuits used to drive inductive loads by utilizing saturating inductors which are connected between switching transistors of the inverter circuit and the inductive load. Circuit elements are also connected to the switching devices of the inverter circuits for initially conducting free-wheeling current through an inductive load upon the turn-off of an inverter transistor.

Abstract: A motor control (10) for a motor (12) powered by an AC pulse source which applies current pulses to stator windings of the motor to cause rotation of the motor in accordance with the invention includes a current sensor (18) for sensing a DC net current in the current pulses flowing to the stator windings; a pulse width modulator (26-58) for pulse width modulating the current pulses; and wherein the width of the pulses is modulated in response to the sensed net current to reduce the net current towards zero.

Abstract: An acceleration system (10) for a brushless DC motor (12) is disclosed having the functional capability of rapid acceleration through one or more mechanical resonance points with electronic commutation of the windings being controlled by pulses generated by sensing the position and rotational velocity of the rotor of the motor and further having the functional capability of synchronous operation in a speed range above the mechanical resonance points. The invention permits rapid acceleration which would be difficult if the motor were accelerated in the synchronous mode of operation controlled by an external pulse source (20). The invention precisely synchronizes switching control of electronic commutation of the windings of a brushless DC motor from pulses generated by a position detector (14) which detects the position and velocity of the rotor to pulses generated by an external signal source which is used during the synchronous mode of operation of the brushless DC motor (12).

Abstract: A variable speed variable torque brushless DC motor (32) having at least one position sensor (34) with each position sensor producing a position signal indicating position of the rotor and having a frequency equal to a frequency of excitation current applied for activating stator windings in accordance with the invention includes a pulse generator (36) for producing first pulses having a frequency which is equal to nf where n is the number of position sensors and f is the frequency of excitation current; a source (39) of a first signal having a frequency f1 wherein f1.gtoreq.f; a source (41) of a variable frequency second signal having a frequency f2 with f2.gtoreq.

Abstract: AC mains voltage input is directed to a bridge rectifier and converted to a DC voltage output. This DC power supplies an inverter which reconverts it to variable frequency AC output, used to drive a variable-speed AC motor.A microprocessor-based control unit generates firing pulses for SCR's in both the rectifier and inverter. It maximizes the efficiency of the rectifier by generating phase delay and sequencing data in advance of each line-to-netural zero-crossover of the AC mains voltage input; it makes the voltage and frequency of the inverter AC output both proportional to the value of the DC voltage output, enabling the system to maintain a constant volts/Hertz ratio between the AC output voltage and the AC output frequency.Appropriate fault protection circuits are included with the control unit to prevent fault conditions from damaging the system.