| 摘要 |
PROBLEM TO BE SOLVED: To stop supply of power to a compressor motor on the occasion when a supply voltage is off a normal range and fluctuates over to a protective operation range. SOLUTION: AC power is rectified by a rectifier circuit 8 and supplied to a compressor motor through an inverter 9. It is inputted as a reference voltage to one input of each of comparators IC1 and IC2 of a comparator circuit 10. Besides, a supply voltage divided by R1 and R2 is inputted directly to the other input of each of the comparators IC1 and IC2. Outputs of the comparators IC1 and IC2 are connected to a photocoupler 11 composed of PC1 and PC2 and an output VOUT of a junction midpoint thereof is supplied to a microcomputer. Zone determination is conducted according to criteria of determination by the comparators IC1 and IC2, and the output VOUT is VH when VAC > reference voltage + a%. The output VOUT is VM when reference voltage + a% >= VAC >= reference voltage - b%, and VOUT is VL when reference voltage -b% > VAC. When the voltage is outside the range, the microcomputer gives an instruction to stop output of the inverter, or a manual stop is conducted. |
