| 摘要 |
PURPOSE:To detect frequency indicating rotation speed simply, by a method wherein when an inverter is out of operation, frequency is detected from residual voltage of a motor and speed control signal is obtained. CONSTITUTION:A memory 8 performs memory action by hold signal in synchronization with switching operation, and terminal voltage of a motor M during OFF-period of a switching transistor 4, i.e., value of residual voltage of the motor M corresponding to frequency, is stored in the memory 8. Voltage proportional to the rotation speed in the memory 8 is fed back as speed control signal to a signal adder ADD, thereby the motor M is rotated at prescribed speed by setting. |
