| 摘要 |
PROBLEM TO BE SOLVED: To drive an electric motor by reliably detecting a back electromotive power waveform that is generated in an armature coil, even when the load of the electric motor is large. SOLUTION: A control means 8 for turning on or off switching means 3a-3f for constituting an inverter circuit 3, application voltage control means 9 for controlling the application voltage of armature coils 4a-4c, voltage detection means 5 for detecting the terminal voltage of the armature coils 4a-4c, comparison means 7 for comparing the output of the voltage detection means 5 with a reference voltage, and reference voltage-setting means 6 for setting a reference voltage are provided. Then, the electric motor 4 is controlled as a synchronous motor, at the same time, an application voltage control means 9 controls the application voltage of the armature coils 4a-4c for a fixed time when the electric motor 4 reaches a specific speed on activation, so that the control means 8 turns the switching means 3a-3f on or off, according to the output of the comparison means 7.
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