说明：  可控硅调压调速原理可控硅调速是用改变可控硅导通角的方法来改变电动机端电压的波形，从而改变电动机端电压的有 效值，达到调速的目的。
(SCR thyristor speed control method is changed to alter the angle of the motor terminal voltage waveform, thereby changing the motor terminal voltage has Efficiency value, achieve the purpose of the governor s.)