| 摘要 |
PROBLEM TO BE SOLVED: To improve safety by enabling prevention of malfunctions of an ATC device caused by the higher harmonics of a main converting device, when the frequency of a power supply fluctuates. SOLUTION: A converter 3 of a main converting device converts AC to DC, controlled with firing pulses using a carrier generated by a carrier wave generating circuit 10 synchronizing with the synchronizing signal of a synchronizing circuit 9. In this case, higher harmonics is generated from the main converting device. Meanwhile, a demodulator 24 demodulates a signal from rails not shown in the figures using a carrier generated from a carrier generator 23 in synchronization with the PLL circuit 22 of an ATC device, thereby providing the demodulated signal for the ATC control. Here, when a time constant is made to mach between the synchronizing circuit 9 and PLL circuit 22, the carrier frequency of the ATC device changes at the same timing with the change of the frequency of the higher harmonics generated from the main converting device, when the frequency of a power supply fluctuates. As a result, the difference between the two preset frequencies remains always unchanged, and the ATC apparatus is prevented from malfunctioning by taking higher harmonics generated from the main converter for a signal. |
