| 摘要 |
PURPOSE:To increase the torque of a motor at the starting time and to reduce the slip of the motor at the time of pulling in its synchronization by decreasing the resistance value of a braking coil provided at a salient pole upon rising of its temperature, thereby varying the characteristic. CONSTITUTION:The electric resistance of a braking coil 3 provided at a salient pole is varied in response to the ambient temperature, and the resistance value is decreased upon rise of the temperature. For example, the braking coil is composed of a main braking coil 301 and an auxiliary braking coil 302, and when the temperature is low, the both coils are isolated via gaps A, B. When the temperature rises, the coils 301, 302 are contacted by the thermal expansion of the coil 301, thereby decreasing the resistance. Since the braking coil resistance is high at the starting time at a low temperature and the resistance of the braking coil is decreased after the starting in this manner, preferable characteristics can be obtained. |
