Electricity: motive power systems – Motor-reversing – Armature or primary circuit control
Patent
1975-03-14
1976-06-29
Rubinson, Gene Z.
Electricity: motive power systems
Motor-reversing
Armature or primary circuit control
318230, 318231, 321 4, 321 9R, H02P 540
Patent
active
039671739
ABSTRACT:
A harmonic reduced pulse width modulation, variable speed transistor bridge inverter drive controls frequency and magnitude of stator voltage applied to an induction motor so as to maintain constant flux in the motor and permit maximum driving torque to be realized from the motor over a wide speed range. An oscillator generates a train of clock pulses whose frequency is proportional to an analog speed signal, and a three phase generator derives three phase reference waves having periods which include a predetermined number of clock pulses. A resettable volt/hertz integrator derives a train of ramp pulses which are synchronized to the clock pulses and vary in magnitude as a function of the integral of the output voltage from the bridge inverter with respect to time. The constant volt/hertz ramp signals are compared to first and second reference voltages to derive phase-displaced first and second control pulses. The fundamental output voltages of individual phases of the bridge are regulated in accordance with respective three phase reference waves, and pulse width modulating means switch the transistors in the phases of the bridge by two different width pulses whose leading edges are established by the clock pulses and whose trailing edges are respectively at the first and at the second control pulses and in such a manner that the bridge inverter applies twelve-step voltages to the motor stator windings in which the fifth and seventh harmonics are substantially eliminated and in which the voltage-to-frequency ratio is controlled to maintain constant flux in the motor.
REFERENCES:
patent: 3387195 (1968-06-01), Piccand et al.
patent: 3538420 (1970-11-01), Klein
patent: 3585488 (1971-06-01), Gutt et al.
patent: 3611086 (1971-10-01), Mokrytzki et al.
patent: 3694718 (1972-09-01), Graf et al.
Allis-Chalmers Corporation
Kaiser Lee H.
Rubinson Gene Z.
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