Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1979-03-14
1981-08-25
Truhe, J. V.
Electricity: motive power systems
Induction motor systems
Primary circuit control
318807, 318800, H02P 534, H02P 742, H02P 528, H02P 536
Patent
active
042862035
ABSTRACT:
A closed-loop drive system for variable speed induction motors for maintaining a constant slip frequency, regardless of motor speed. A slip frequency oscillator generates a signal having a frequency proportional to the desired slip of the motor and a tachometer generates a signal having a frequency proportional to the actual rotational speed of the motor. The stator frequency is the sum of the rotor speed and the slip frequency during acceleration and the difference between the rotor speed and the slip frequency during braking. Exclusive OR gates are used to add the slip frequency signal either to the tachometer signal or to the stator signal, the outputs of the gates being applied to a digital phase detector. The phase detector drives a voltage controlled oscillator which provides the stator signal. The output of the voltage controlled oscillator is used to trigger the slip frequency oscillator to prevent overlap of pulses to the digital phase detector.
REFERENCES:
patent: 3568022 (1971-03-01), Domann et al.
patent: 3731169 (1973-05-01), Burgholte et al.
patent: 3983463 (1976-09-01), Nabae et al.
patent: 4042862 (1977-08-01), Franklin
Beckman Instruments Inc.
Conklin John B.
Mehlhoff F. L.
Steinmeyer R. J.
Stern Robert J.
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