CONTROLLER FOR LOAD ROTATING SPEED

PURPOSE:To rapidly convert one to the other of power converters normally or reversely by obtaining an induced voltage indirectly by utilizing a firing angle, a current average value and a momentary current value at power converter switching time, thereby eliminating a detector. CONSTITUTION:Conversion preparing means 14 of a power converter stores in advance a relationship between a firing angle and the induced voltage of a load for a current average value over one period, obtains the induced voltage of a load from the actual firing angle value, the current average value and the momentary current value of a power converter during operation at that time when switching the power supplying direction of the converter, and forms the initial value 15 of the firing angle of the power converter after switching by utilizing the value. A current controller 4 starts the current control with the value as a firing command 5.