METHOD OF CONTROLLING PREHEATING POWER AND MECHANISM FOR PROVIDING PREHEATING

摘要

The invention relates to a method of keeping constant the power consumption required for preheating a motor, especially a compressor motor of an air conditioner. The switching control of an inverter (15) for supplying 3-phase currents to a motor (30) is performed by a control circuit (20) according to the duty factor obtained based on a detected voltage value (Vm) and a detected current value (Im). The duty factor decreases as supply voltage increases. According to this method, a motor can be effectively preheated independently of fluctuations in supply voltage.