| 摘要 |
PURPOSE:To realize improvement in the reliability of the whole device by positively preventing the situation of the abnormal rise of the temperature of device itself even when operation is continued as a forced cooling means for cooling a heating element is left as it is stopped. CONSTITUTION:A full-wave rectifier circuit 1 and an inverter main circuit 4 are cooled by radiation fins and a fan device 6. A temperature detector 7 outputs a temperature signal Sd at a voltage level corresponding to the temperature of the radiation fins. When the relationship of Sd>=Vref1 holds in the temperature signal Sd and a preset overheat detecting temperature Tmax, a comparator 8 outputs an overheat detecting signal Soh, and stops the operation of an inverter device. An aritttmetic circuit 9 outputs a rise-rate signal DELTAd at a voltage level corresponding to the rate of the temperature rise of the radiation fins detected on the basis of the temperature signal Sd. A comparator 10 compares the rise-rate signal DELTAd and a reference voltage signal Vref2 corresponding to a maximum temperature-rise rate DELTAmax and outputs an abnormal temperature-rise detecting signal Sa when the relationship of DELTAd>=Vref-2 holds. |
