What is a Synchronous Motor?

A synchronous motor is an AC motor that generates torque by the interaction of the excitation magnetic field supplied by a direct current and the rotating magnetic field of the armature, and rotates at a synchronous speed.) is an AC motor that generates torque by the interaction of the DC-powered excitation magnetic field and the rotating magnetic field of the armature, which rotates at a synchronous speed.

A synchronous motor is an AC motor that generates torque by the interaction of the excitation magnetic field supplied by a direct current and the rotating magnetic field of the armature, and rotates at a synchronous speed.) is an AC motor that generates torque by the interaction of the DC-powered excitation magnetic field and the rotating magnetic field of the armature, which rotates at a synchronous speed.

An AC motor in which the rotation of the rotor is the same as the rotation of the stator's rotating magnetic field. The rotor speed n, the number of magnetic pole pairs p, and the power supply frequency f satisfy n=60f/p. The speed n is determined by the power frequency f, so when the power frequency is constant, the speed does not change and has nothing to do with the load. It has the characteristics of high operating stability and large overload capacity. Commonly used in multi-machine synchronous transmission systems, precision speed regulation and speed stabilization systems and large equipment (such as rolling mills), etc.

Synchronous motors are AC motors, and the stator windings are the same as asynchronous motors. Its rotor rotation speed is the same as the speed of the rotating magnetic field generated by the stator winding, so it is called a synchronous motor. Because of this, the current of the synchronous motor is ahead of the voltage in phase, that is, the synchronous motor is a capacitive load. For this reason, in many cases, synchronous motors are used to improve the power factor of the power supply system.

Because the synchronous motor can run at a leading power factor by adjusting the excitation current, it is beneficial to improve the power factor of the power grid. Therefore, large-scale equipment, such as large-scale blowers, water pumps, ball mills, compressors, rolling mills, etc., are commonly driven by synchronous motors. This advantage is particularly prominent when a synchronous motor is used in a large-scale equipment with a 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 also constant, and it does not change with the load. This feature is of great significance in certain transmission systems, especially multi-machine synchronous transmission systems and precision speed regulation and speed stabilization systems. The operating stability of the synchronous motor is also relatively high. Synchronous motors generally run under over-excitation, and their overload capacity is greater than that of corresponding asynchronous motors. The torque of an asynchronous motor is proportional to the square of the voltage, while the torque of a synchronous motor is determined by the product of the voltage and the internal electromotive force generated by the motor's excitation current, that is, it is only proportional to the first power of the voltage. When the grid voltage suddenly drops to about 80% of the rated value, the asynchronous motor torque often drops to about 64%, and stops running due to the immobile load; while the synchronous motor torque does not drop much, and it can be forced Excitation to ensure the stable operation of the motor.

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