A means for controlling the output torque condition of a synchronous reluctance motor. The means comprises a motor control having a first signal means generating a torque command signal and a second signal means providing a rotor frequency signal. A stator winding energization means is coupled to the signal means for providing a stator current of a desired frequency and phase displacement to the motor. A power supply means is coupled to the stator winding energization means for regulating the magnitude of the stator current to a predetermined value responsive to the first signal means. The invention also obtains the speed control of self excited alternating current motors.
CROSS REFERENCE TO RELATED APPLICATION
The present application is a divisional application of copending application Ser. No. 82,302, filed Oct. 20, 1970 and now abandoned.
A reluctance motor control system is stabilized by a load angle feedback control loop provided by a computation of the load angle from sensed voltage and current on the terminals of the motor with the assist of a derived frequency signal. The motor is operated at most efficient load angle in motoring or braking, while the motor voltage is being controlled so as to maintain the desired load angle as the speed and/or load vary.
A method and an apparatus for driving and controlling a synchronous motor using permanent magnets as its field system are herein disclosed. When a rotational speed of the synchronous motor using the permanent magnets as the field system is more than a base rotational speed, a current condition computing section computes a field weakening reference current in accordance with a battery voltage, a reference torque and a rotational speed. An inverter performs the field weakening control of the the synchronous motor using the permanent magnets as the field system in accordance with the field weakening reference current sent from the current condition computing section to prevent the deterioration of efficiency and the deficiency of output due to the excessive or insufficient field weakening current. The current condition computing section determines optimum reference current by the use of a converged battery voltage, when the battery voltage is converged to a constant value after initial control.
A tachometer is coupled to the rotor of an A.C. motor and generates an output voltage proportional to the rotor's speed. A VELOCITY COMMAND voltage is generated having an amplitude which specifies a desired rotor speed. The tachometer voltage is subtracted from the VELOCITY COMMAND voltage to produce a VELOCITY ERROR voltage. The output of a D.C. power source is chopped at a fixed frequency and variable pulse width, the pulse width being proportional at any time to the amplitude of the VELOCITY ERROR voltage. The chopped D.C. voltage is filtered to provide a variable D.C. voltage having an amplitude which is proportional to the amplitude of the VELOCITY ERROR voltage. The variable D.C. voltage is applied to an inverter which changes it into an A.C. voltage. The A.C. voltage is applied to the stator windings of the motor to drive the rotor thereof. The frequency of the A.C. voltage is variable and is proportional, at rotor speeds above 150 RPM, to the amplitude of the velocity command voltage. At rotor speeds below 150 RPM, the frequency of the A.C. voltage is held fixed at approximately 28 Hz. The amplitude of the A.C. voltage is proportional to the VELOCITY ERROR voltage at all speeds. The frequency of the A.C. voltage is determined by an oscillator which drives a ring counter whose counting direction is controlled by a direction flip-flop. The state of the direction flip-flop is changed whenever the polarity of the VELOCITY ERROR voltage changes so that deceleration of the motor always occurs in a plugging mode.
A device for controlling a variable speed motor includes a chopper including a switch for modulating by variable width pulses a rectified a.c. voltage. At least one winding of the motor forms, with a capacitor for filtering out the switching peaks of the switch a first cell for filtering out radio frequency perturbations generated by the switching of the switch.
