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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.
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.
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.
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. |
Conclusion
When we compare the working of both the machines, we found that an induction motor is fundamentally a transformer in which the stator winding acts as the primary winding and the rotor winding acts as the secondary winding. Also, the mathematical analysis of both the machine is almost same.
The most significant difference that we can state between an induction motor and a transformer is that an induction motor converts electrical energy into mechanical energy while a transformer converts electrical energy of a voltage level into electrical energy of another voltage level.
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