| 摘要 |
PURPOSE:To suppress induction of electromotive force as low as possible by temporarily interrupting a control relay in synchronism with an interruption signal and switching relay contacts when power supply to a fan motor, is temporarily interrupted. CONSTITUTION:A control relay 3. to which DC voltage 12V supply is interrupted, is turned OFF through zero-cross function at a zero-cross point of source voltage waveform. i.e., a time point when an interruption signal makes a transition from H to L. Upon provision of a second interruption signal after turn OFF of the control relay 3. a microcomputer 4 switches the input levels from H to L for one or a plurality of inverters out of three inverters 8. 9, 10, required for switching the rotational sped of a fan motor 2, thereby interrupting DC voltage 12V supply to corresponding relay coils thus switching the corresponding relay contacts. Upon switching of relay contacts, input level of an inverter 7 is returned from L to H based on a next interruption signal so that the control relay 3 is fed with DC voltage 12V and reset thus feeding the fan nectar 2 with power from a commercial power supply 1. |
