| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a small, cost-effective coil switching device for a three-phase AC motor that eliminates distortion of a motor current, with regard to a problem that an unnecessary current is caused to normally flow in snubber circuits incorporated to consume residual energy of motor coils which is generated when the coils are switched and as a result the motor current is distorted. <P>SOLUTION: In coil switching portions, semiconductor switches are inserted in current paths between full-wave rectification portions and the snubber circuits and the timing of turning off the switches are delayed by an arbitrary period of time from the instance the motor coils are shifted from an excitation state to a non-excitation state. By doing so, the snubber circuits are put into a conducting state to consume the residual energy of the motor coils during the period of time only when the energy are discharged. By putting the circuits into a non-conducting state during the period of time other than the energy-discharging period, the unnecessary current flow can be prevented and the distortion of the motor current can be eliminated. <P>COPYRIGHT: (C)2008,JPO&INPIT |
