Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1981-11-04
1984-07-03
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Primary circuit control
363 41, H02P 540
Patent
active
044581947
ABSTRACT:
An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a "flyback" DC-DC converter circuit for recharging the battery.
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"Introduction to PWM Speed Control System for 3-Phase AC Motors", Electronic Components and Applications, vol. 2, No. 2, Feb. 1980, pp. 5-18.
"LSI Circuit for AC Motor Speed Control", Electronic Components and Applications, vol. 2, No. 4, Aug. 1980, pp. 32-42.
Geppert Steven
Slicker James M.
Eaton Corporation
Grace C. H.
Lewis J. G.
Smith Jr. David
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