| 摘要 |
PURPOSE:To enhance the precision of the timing of switching, by switching the star connection of an induction motor to the delta connection, when current flowing through a main circuit is stabilized. CONSTITUTION:When an operation switch 13 for start is turned ON, then excitation coils 4a, 5a are excited by an arithmetic circuit section 12, and an induction motor 1 is started to be electrically communicated in the state of star connection. When main circuit current Ic detected by a current detection means 8 is not changed for a given or more time, then the current conduction of the excitation coil 5a is stopped. Besides, after the lapse of a specified time, current is conducted to an excitation coil 6a, and the electrical conduction of the induction motor 1 is switched to that in the state of delta connection. As a result, the timing of switching can be easily set.
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