| 摘要 |
PURPOSE:To prevent production of higher harmonics by detecting zero cross of an AC power supply by means of one of a plurality of main motors driven with a VVVF power, obtained by inverting a DC power obtained through rectification of an AC power, and then transmitting thus detected zero cross point as a synchronizing signal to other main motor. CONSTITUTION:AC power taken in through a pantograph 1 and a transformer 2 is subjected to PWM conversion 4 and smoothed 5 to produce a DC power which is then inverted through an inverter 6 to produce a VVVF power for driving a motor 7. Zero cross point of the AC power supply is detected 9 through an Otto filter 8 to generate a synchronizing signal for driving the PWM converter 4 through a gate control circuit 10. The zero cross point is also fed from the driver 13 in a master unit 11 on a synchronizing line 17 to receivers 14 in a plurality of other slave units 12. A watch dog timer 15 in the slave unit 12 detects the phase difference of the synchronizing signal and when thus detected phase difference is within a predetermined range, a gate control circuit 10 is controlled by a signal fed from the receiver 14. |
