| 摘要 |
An electronic system for controlling the speed of a shaded-pole single-phase induction motor provides increased power during speed increase and automatic braking during slowdown by regulation of half-wave D.C. braking current applied to the motor. Speed control during normal operation, and braking control during slowdown and stopping, are implemented by means of dual feedback loops interactively connected to the gate electrode of a triac in the A.C. current line of the motor. The speed control loop utilizes a frequency/phase detector to adjust the time delay of triac gating relative to the zero crossing points of each half-cycle of A.C. voltage until the tachometer-sensed speed of the motor corresponds to a desired speed set by a voltage controlled oscillator. The braking control loop adjusts the time delay of the triac gating relative to the zero crossing points of every alternate half-cycle of A.C. power thus decelerating the motor by an impressed half-wave pulsed D.C. current.
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