As the synchronous motor can operate under the advanced power factor by adjusting the excitation current, and benefit the power grid improving the power factor. It enjoys a wide range of application in large-scale equipment from large blower, pump to compressor and rolling mill.
This characteristic is particularly prominent in the use of synchronous motor in large equipment with low speed. In addition, the speed of the synchronous motor is completely determined by the power frequency. When the frequency is constant, the speed of the motor is certain, and it does not change with the load. This characteristic is crucial in some of the transmission system, especially in the multi machine synchronous transmission system and precise speed control system. Otherwise, It also characterized by high stability.
The synchronous motor is usually operated under the excitation condition, and the overload capacity of the motor is larger than the corresponding asynchronous motor. Compared with induction motor, the torque is decided on the product of voltage and motor excitation currents generated within the electromotive force, namely, the torque is only proportional to the voltage. While that of the asynchronous motor is proportional to its voltage’s square. When the power grid voltage suddenly drops to 80% of the rated value, the asynchronous motor torque is often reduced to 64% and gradually stops for it is out of the load. In the same circumstance, the AC synchronous motor can still be in stable state through the force excitation.