Difference Between Induction Motor and Synchronous Motor: Key Distinctions Explained

Understanding the differences between induction motors and synchronous motors is crucial for selecting the right type of motor for various industrial applications. Both types of motors are widely used in the industry, but they operate on different principles and have distinct characteristics. This article explores the key distinctions between induction motors and synchronous motors to help you make informed decisions.

Definition and Overview of Induction Motors

What is an Induction Motor?

An induction motor, also known as an asynchronous motor, operates on the principle of electromagnetic induction. It is the most common type of AC motor used in various applications due to its simplicity and durability.

How Induction Motors Work

Induction motors work by inducing an electromagnetic field in the rotor through the stator’s rotating magnetic field. The rotor does not receive electrical power directly; instead, it rotates due to the induced current caused by the stator’s magnetic field.

Types of Induction Motors

  • Single-Phase Induction Motor: Used in domestic appliances and small machinery.
  • Three-Phase Induction Motor: Commonly used in industrial applications due to its efficiency and power.

Definition and Overview of Synchronous Motors

What is a Synchronous Motor?

A synchronous motor is an AC motor that operates at a constant speed, synchronized with the frequency of the supply current. Unlike induction motors, synchronous motors run at a speed equal to the supply frequency.

How Synchronous Motors Work

Synchronous motors operate by applying a three-phase AC supply to the stator, which generates a rotating magnetic field. The rotor, typically containing windings or permanent magnets, is magnetically locked with the rotating field and rotates at the same speed as the stator’s magnetic field.

Types of Synchronous Motors

  • Non-Excited Synchronous Motor: Uses permanent magnets in the rotor.
  • Direct-Current (DC) Excited Synchronous Motor: Requires a DC power source for the rotor windings.

Key Differences Between Induction Motors and Synchronous Motors

Principle of Operation

  • Induction Motor: Operates based on electromagnetic induction where the rotor current is induced by the stator’s magnetic field.
  • Synchronous Motor: Operates by synchronizing the rotor speed with the stator’s rotating magnetic field.


  • Induction Motor: Speed varies with the load and is always less than the synchronous speed.
  • Synchronous Motor: Runs at a constant speed regardless of the load, equal to the synchronous speed.


  • Induction Motor: Generally less efficient due to slip and rotor losses.
  • Synchronous Motor: More efficient, especially under high load conditions, as there is no slip.

Starting Mechanism

  • Induction Motor: Simple starting mechanism, often self-starting.
  • Synchronous Motor: Requires additional starting mechanisms such as an auxiliary motor or damper windings.


  • Induction Motor: Widely used in pumps, fans, compressors, and conveyor systems.
  • Synchronous Motor: Used in applications requiring constant speed such as clocks, record players, and industrial drives.

Pros and Cons of Each

Induction Motor


  • Robust and durable.
  • Lower cost and easier to maintain.
  • Lower efficiency due to slip.
  • Speed varies with load.

Synchronous Motor


  • High efficiency with no slip.
  • Constant speed operation.
  • More complex starting mechanisms.
  • Higher initial cost and maintenance requirements.

Comparison Table

To better illustrate the differences, here’s a comparison table:

FeatureInduction MotorSynchronous Motor
Principle of OperationElectromagnetic inductionSynchronization with the stator’s magnetic field
SpeedVaries with load, less than synchronous speedConstant speed, equal to synchronous speed
EfficiencyGenerally less efficient due to slipMore efficient, especially under high load
Starting MechanismSimple, often self-startingRequires additional starting mechanisms
ApplicationsPumps, fans, compressors, conveyor systemsClocks, record players, industrial drives
ProsRobust, durable, lower cost, easy to maintainHigh efficiency, constant speed operation
ConsLower efficiency, speed varies with loadComplex starting, higher cost, more maintenance
Comparison table illustrating the difference between induction motor and synchronous motors.


In summary, while both induction motors and synchronous motors have their unique advantages and are suited for different applications, your choice will depend on the specific requirements of your project. Induction motors are favored for their simplicity and cost-effectiveness, whereas synchronous motors are chosen for applications needing constant speed and higher efficiency.

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