| 摘要 |
In this system, a controlled rectifier converter interconnects an alternating current voltage source with an AC induction motor. To effect voltage amplitude control, trigger signals are pulsed to the various controlled rectifiers of the converter during their respective 120 DEG conductive intervals. The resultant duty cycle modulation affords control of the level of the voltage applied to the induction motor. At low frequencies, a plurality of power pulses are provided by the converter during each 60 DEG of conduction, whereas at high frequencies, a single power pulse is supplied for each 60 DEG of conduction. A smooth transition is provided between these two operating modes to ensure smooth, continuous motor control and operation throughout the operating range of the motor. This smooth transition is facilitated by synchronizing the power pulses in relation to the two 60 DEG increments comprising the 120 DEG conductive intervals for the respective controlled rectifiers.
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