Difference between Induction Motor and Transformer

What Is The Difference between Induction Motor and Transformer? . Both transformers and induction motor both are the most extensively used electrical machines in practice. The transformer is an electromagnetic static machine while the induction motor is an electromechanical energy conversion device. Since the induction motor and transformer are functionally quite similar because both work on the Faraday’s law of electromagnetic induction, therefore it is required to understand the differences between them.

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In this article, we will highlight all the significant differences between an induction motor and a transformer. Let’s start with some basics first so that it becomes easier to understand the differences between them.

What is an Induction Motor?

An electrical machine which converts electrical energy input into mechanical energy output is known as electric motor. That electric motor which works on the principle of electromagnetic induction between two different windings is known as induction motor.

An induction motor is a type of asynchronous AC motor. Which means, the rotor of the induction motor can never rotate at the speed of magnetic field, i.e., synchronous speed.

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A typical induction motor consists of two windings namely stator winding and rotor winding. The AC electric supply is fed to the stator winding of the induction motor which produces a rotating magnetic field. This RMF (rotating magnetic field) interacts with the rotor winding, which is usually a short-circuited winding, to induce a current in the rotor winding. This induced rotor current also produces a magnetic field in the machine. When the magnetic fields of the stator and rotor interacts with each other, an electromagnetic torque is produced on the rotor, which turn the motor shaft. In this way, an induction motor converts AC electricity into mechanical energy.

Induction motors are mainly used to drive the mechanical loads in domestic and industrial applications like driving pumps, conveyors, electric vehicles, electric traction, fans, compressors, etc.

What is a Transformer?

A transformer is a static electrical machine which is used for transforming the level of voltage or current in an electric circuit. It is a static machine because it does not consists of any moving part to perform its operation.

A typical transformer consists of two winding namely primary and secondary wound on a common magnetic core made up of soft magnetic material. The input AC electrical energy is given to the primary winding which sets up an alternating magnetic field in the core and links to the secondary winding. An alternating EMF is induced in the secondary winding according to the Faraday’s law of electromagnetic induction. The value of secondary winding EMF depends on the number of turns in the winding. In this way, the transformer changes the level of voltage and current of the AC electric supply with the help of electromagnetic induction.

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Hence, from the basics description of the induction motor and transformer. It is clear that both the machines have two windings, which is connected to the AC electric supply and another is the one in which current is induced by the process of electromagnetic induction.

Difference between Induction Motor and Transformer

Both induction motors and transformers work on the principle of electromagnetic induction, however there are many differences between them that are highlighted in the following table

Basis of Difference	Induction Motor	Transformer
Definition	An induction motor is an electrical machine which converts AC electrical energy into mechanical energy.	A transformer is an electrical machine which converts low voltage or current AC supply into high voltage or current AC supply and vice-versa.
Moving parts	Induction motor contains moving parts called rotor. Hence, it is a rotating electrical machine.	Transformer does not contain any moving part. Hence, it is a static electrical machine.
Main components	Induction motor consists of two main components namely stator and rotor.	The major components of a transformer are magnetic core, primary winding and secondary winding.
Primary function	The primary function of an induction motor is to produce mechanical power to drive the mechanical loads.	The primary function of a transformer is to increase or decrease the voltage or current level of AC supply.
Windings	Induction motor has two winding namely stator winding and rotor winding. Where, the stator winding acts as primary and rotor winding acts as secondary.	Transformer has two windings namely primary and secondary. Where, input is given to primary and output is taken from secondary.
Frequency of induced emf in secondary winding	In case of induction motor, the frequency of secondary winding (rotor winding) emf is variable and it depends on the load on the motor.	In a transformer, the frequency of induced emf in the secondary winding remains constant and it does not depend on the load.
Input and output	The input of an induction motor is electrical energy. Whereas, the output is the mechanical energy.	The input of a transformer is electrical energy, while the output is also electrical energy.
Magnetic field	The magnetic field in case of an induction motor is a rotating magnetic field.	The magnetic field in a transformer is an alternating magnetic field.
Air gap	An air gap exists between stator and rotor of an induction motor.	There is no air gap in case of transformer.
Path of magnetic flux	In an induction motor, the magnetic flux completes its path through the air gap.	In a transformer, the magnetic flux completes its path through iron core.
Power factor	The power factor of an induction motor is always predefined by the manufacturer and it is always lagging.	The power factor of a transformer is determined by the load. Hence, a transformer can operate at any kind of power factor like lagging, leading or unity.
Rating	Induction motor is always rated in kilowatt (kW).	The rating of a transformer is specified in kilo volt ampere (kVA).
Efficiency	The efficiency of an induction motor is always less than that of a transformer.	Transformer has relatively high efficiency due to absence of moving parts.

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Basic Difference between Induction Motor and Transformer

1. A Transformer is a static device, whereas motor is a dynastic machine contains on moving parts.
2. A transformer transfers electrical power from one circuit to another without changing the supply frequency, i.e. it only step-up or step-down the level of voltage and current, whereas induction motor converts electrical power into mechanical power.
3. In a transformer, the frequency of induced EMF and current in the secondary is same as supply frequency, i.e. primary and secondary frequency is constant while in an induction motor, the frequency of current and EMF on stator remains same, whereas the frequency of the rotor is variable which depends on slip and slip is further depends on motor loads. The frequency of induced EMF on the rotor is equal to slip times the stator frequency.
4. In a transformer, both the input and output energy (primary and secondary) is in the form of electrical energy, whereas in motor, the supply energy in the rotor is in electrical form and the stator energy converted to the mechanical form of energy.
5. A transformer is an alternating flux machine while induction motor is a rotating flux machine.
6. In a transformer, mostly a ferromagnetic iron core is used as a medium for the passage of flux from primary to secondary, whereas in an induction motor, the air gap is used between rotor and stator.
7. A transformer can be operated at any kind of power factor depends on load while induction motor operated on lagging power factor because it draws lagging current to magnetize the rotor filed at starting and operating due to air gap.
8. A transformer efficiency is always higher than the induction motor efficiency because there is no moving parts in a transformer, whereas mechanical losses occurs in an induction motor as it is not static machine like a transformer.

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FAQs About Transformers and Induction Motors

1. Can transformers operate on DC power?

No, transformers require alternating current (AC) to induce voltage changes via electromagnetic induction.

2. What are the common materials used in transformer cores?

Transformers typically use laminated silicon steel cores to reduce eddy current losses.

3. Why are induction motors called asynchronous?

Induction motors are termed asynchronous because the rotor speed is slightly less than the synchronous speed of the stator field.

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