Working Principle of Synchronous Motor: Stator, Rotor & Synchronism
Understand the working principle of synchronous motors with stator field, rotor excitation, synchronism with AC frequency, and common start techniques.
A synchronous motor is an AC motor that rotates its rotor at a constant speed. Its speed is synchronised with the frequency of the power supply. It converts electrical energy into mechanical energy and is commonly used in constant-speed applications.
In this blog, we will explore the working principle of synchronous motors and their applications across various industries. It will help you understand how a synchronous motor works and maintains constant speed throughout operation.
Synchronous Motor Working Principle
Synchronous motor working principle is based on the interaction between the magnetic fields of the stator and rotor.
When AC power is supplied to the stator windings, it generates a rotating magnetic field (RMF). The RMF moves at a constant speed and is synchronised with the frequency of the power supply.
The rotor has its own magnetic field produced by permanent magnets in the windings. When the stator’s magnetic field rotates, it interacts with the rotor's magnetic field and pulls the rotor with it.
Once the rotor matches the speed of the stator’s magnetic field, both fields lock together and rotate at the same speed.
Let’s take an example: a synchronous motor is driving an industrial machine. If the load increases, the motor does not reduce its speed. Instead, its magnetic field creates a greater angle and allows the motor to produce motor torque at the same speed.
Synchronous Motor Applications
Synchronous motors are used in a wide variety of applications where constant speed and precision are necessary. Some applications are:
- Synchronous motors are used in industrial applications such as pumps, fans & blowers, compressors and machines where constant speed is required.
- They also support manufacturing and processing industries such as paper and textile machinery, rolling mills, and other machine tools for continuous operation.
- They also work as synchronous condensers in power factor correction to improve the efficiency of power systems.
Frequently Asked Questions
Q1. What is the difference between Synchronous Motors and Induction Motors?
Synchronous motor runs at synchronous speed, while induction motor runs slightly below synchronous speed when the load increases. Synchronous motors require separate excitation, and induction motors require electromagnetic induction.
Q2. Is Synchronous Motor AC or DC?
Synchronous motor is an AC motor. When AC power is supplied to its winding, it creates rotating magnetic field that interacts with the rotor and moves at constant speed.
Q3. What are two main types of Synchronous Motor?
Two main types of synchronous motors are DC-excited synchronous motor and non-excited synchronous motor. A DC-excited motor requires an external DC source to energise the windings and create rotation. Non-excited synchronous motor uses permanent magnets for rotation.
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