| 摘要 |
A power factor control circuit is disclosed which is relatively immune to variation in the current through the winding of the motor. This is accomplished by controlling the triac firing circuits as a function of the zero crossing of motor current. For single phase motors the circuit consists of voltage and current squaring means, the outputs of which are provided through logic gates to a summing amplifier. The output of the summing amplifier is an error voltage proportional to the phase difference between the line voltage and the motor current. A control voltage, generated as a function of the zero crossing of the motor current waveform, causes firing of the triac circuit when the ramp exceeds the value of the error signal.
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