What is the Difference Between Synchronous and Asynchronous Motor?
🆚 Go to Comparative Table 🆚The main difference between synchronous and asynchronous motors lies in their rotation speed, stator and rotor synchronization, and starting methods. Here are the key differences between the two:
- Synchronous Motor:
- Rotor speed and stator magnetic field speed are equal, resulting in no slip.
- Requires an additional input supply for the rotor to produce a magnetic field.
- Has a constant speed that does not depend on the load.
- Not self-starting and requires external means for starting.
- Examples include brushless motors, variable reluctance motors, switched reluctance motors, and hysteresis motors.
- Asynchronous Motor:
- Rotor speed is less than the synchronous speed, resulting in slip (slip is always greater than 0).
- Does not require an additional input supply for the rotor.
- Speed depends on the load, rotor resistance, and slip.
- Self-starting and does not require external means for starting.
- Also known as an AC induction motor.
In summary, synchronous motors have a constant speed and require an additional input supply for the rotor, while asynchronous motors have a variable speed depending on the load and are self-starting. Synchronous motors are used in specialized applications like power factor correction and driving loads at constant speed, while asynchronous motors are used in various general-purpose applications.
Comparative Table: Synchronous vs Asynchronous Motor
Here is a table comparing the key differences between synchronous and asynchronous motors:
Feature | Synchronous Motor | Asynchronous Motor |
---|---|---|
Definition | A synchronous motor is an AC machine whose rotor speed is synchronized with the rotatory magnetic field of the stator. | An asynchronous motor is an AC machine whose rotor speed is not synchronized with the rotatory magnetic field of the stator. |
Speed of Rotor | The rotor speed of the synchronous motor is the same as that of the rotational speed of the stator. | The rotor speed of the asynchronous motor is less than that of the rotational speed of the stator, i.e., N < NS. |
Slip | Synchronous motors do not have slip, meaning their rotors move in sync with the stator's magnetic field. | Asynchronous motors have slip, meaning there is a difference between the rotor's speed and the stator's magnetic field speed. |
Type | Synchronous motors include brushless motors, variable reluctance motors, switched reluctance motors, and hysteresis motors. | Asynchronous motors are also known as AC induction motors. |
Starting | Synchronous motors are not self-starting and require an external means of starting, such as a damper winding to provide starting torque. | Asynchronous motors are self-starting and do not require any additional starting source. |
Rotor Supply | The rotor of a synchronous motor requires an extra input supply to produce the rotor magnetic field. | In the case of asynchronous motors, if the rotor is squirrel cage type, only one input supply is required. |
Speed and Load | The speed of the synchronous motor does not vary with the variation in the load. | The speed of an asynchronous motor varies with the change in the load. |
Applications | Synchronous motors find applications in power factor correction and operation of mechanical loads. | Asynchronous motors are used only to operate mechanical loads. |
In summary, the main difference between synchronous and asynchronous motors lies in the speed and synchronization of their rotors compared to the stator's magnetic field. Synchronous motors have a rotor speed that matches the stator's magnetic field, while asynchronous motors have a rotor speed that is less than the stator's magnetic field speed.
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