摘要 |
In order to carry out commercial synchronous exchange for disconnecting an induction motor from its driving power supply and connecting it to a variable frequency power supply or commercial synchronous switching for disconnecting the induction motor from the variable frequency power supply and connecting it to a commercial power supply without any accompanying adverse shock, an induction-motor vector control technique is utilized and furthermore, a phase-locked loop (PLL) is formed to detect the difference in phase between the phase of the output voltage from the variable frequency power supply or the magnetic flux phase of the induction motor on the one hand, and the phase of the voltage of the power supply on the other, so that the difference in phase thus detected can be maintained at a predetermined value.
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