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Difference between Reluctance Motor and Induction Motor
Electric motors are present in the industry to help us to drive a lot of numbers of mechanical loads in the industry. They have a moving and stationary part to interact with the magnetic field and current to transform electric energy into mechanical energy. They have dominated the industry from automobiles to robotics and household to industrial applications.
In this tutorial, we will explore the important differences between a reluctance motor and an induction motor. The most fundamental difference between a reluctance motor and an induction motor is that a reluctance motor operates on the principle of magnetic reluctance while the induction motor operates on the principle of electromagnetic induction. Before going to discuss the differences between reluctance motor and induction motor, let us first get a brief overview of reluctance motor and induction motor individually.
What is a Reluctance Motor?
We will try to understand the concept of magnetic reluctance before getting into the reluctance motor. It is represented by the opposition in the way of magnetic flux offered by a specific material. We can understand reluctance as the measurement of the difficulty level in the way of magnetic field lines passing from a subject.
The reluctance motor is defined as a type of electric motor that works on the principle of magnetic reluctance to drive a specific load connected with a shaft. The magnetic reluctance principle activates the rotor to rotate with the lowest reluctance (opposition) and then maximize magnetic flux. A reluctance motor produces high torque with temporary poles on the rotor.
Reluctance motors utilize the principle of electromagnetic reluctance. These motors have salient poles inside the rotor and stator part of the motor. Due to the salient poles, this motor becomes able to produce a difference between the aligned and misaligned positions. This is how the difference between stator and rotor reluctance enables to rotor of the motor to align with minimum reluctance. This reluctance then creates a rotational force within the rotor to drive heavy loads. Its rotor is made up of soft materials of magnets like silicon steel.
When the stator is present at an equal distance from the two adjacent rotor poles, it is called the unaligned position of poles and gives maximum magnetic reluctance. On the other hand, in an aligned position, two or more rotor poles are aligned with two or more stator poles and gives minimum reluctance.
These motors carry lesser numbers of windings and are quite easy to construct due to the use of magnetic reluctance properties in their operation.
These motors are further divided into synchronous reluctance motors, switched reluctance motors, and variable reluctance motors. The reluctance motors excel in high-speed applications in the industry and are used in the automotive industry due to providing high power at a relatively lower cost.
What is an Induction Motor?
An induction motor utilizes the principle of electromagnetic induction to produce a rotational force. These motors are the types of alternating current (AC) motors.
In an induction motor, the electric current is produced using the electromagnetic induction principle within the rotor winding by the stator magnetic field. After that process, the current produces torque in the rotor to drive the mechanical loads. These loads can lie in numerous applications in our real life of innovation and modernism. Here are two types of rotor configurations in an induction motor namely, squirrel cage type rotor and wound type rotor.
These motors do not operate at the synchronous speed of the magnetic field of the stator. Due to a mismatch in both speeds, the motor speed and motor’s magnetic field speed, i.e. synchronous speed, induction motors are also called asynchronous motors.
We provide one supply in this motor to the stator part and the magnetic field is produced due to passing current through a current-carrying winding or coil. The rotor gets its magnetic field from the stator and due to electromagnetic induction, the magnetic field passing through the rotor produces a current in the rotor (as the rotor is a short circuited) using electromagnetic induction. Therefore, induction motors work by electromagnetic induction of magnetic field by passing current through motor windings.
These motors are further classified into single-phase motors, three-phase motors, split-phase motors, and slip-ring induction motors. These motors find their applications in cranes, automobiles, home appliances like mixers and pumps, and many other industrial equipment.
Difference Between Reluctance Motor and Induction Motor
The key differences between reluctance motor and induction motor are explained in the following table −
Parameter |
Reluctance Motor |
Induction Motors |
|---|---|---|
Type |
The reluctance motor is a type of single-phase synchronous motor. |
The induction motor is under asynchronous AC motor. |
Working principle |
Reluctance motor operates on the principle of magnetic reluctance, where the rotor minimizes reluctance. |
Induction motor operates on the principle of electromagnetic induction where a rotating magnetic field induces current in the rotor. |
Construction |
Reluctance motors are relatively simple to design and construct as they have salient poles and lesser windings. |
Induction motors are relatively complex to design and construct than reluctance motor, as they use larger number of windings. |
Torque produced |
Reluctance motors produce lesser torque than induction motors. |
Larger torque is produced by an induction motor, when compared to a reluctance motor. |
Speed control |
Reluctance motors offer precise speed control. |
Induction motors offer limited speed control and require VFD (Variable Frequency Drives). |
Efficiency |
Reluctance motor has higher efficiency. |
The efficiency of induction motors is less due to losses in electromagnetic induction process. |
Applications |
Reluctance motors are used for high-speed applications where precise control is required. |
Induction motors are widely used in industrial and home appliances, such as in pumps, conveyors, mills, mixers, fans, air compressors, etc. |
Rotor design |
Reluctance motors have salient pole rotor. |
Induction motors have two types of rotor designs namely, squirrel cage rotor and wound rotor. |
Torque-speed characteristics |
Reluctance motor has linear speed torque characteristic. |
Induction motor has non-linear torque-speed characteristic. |
Starting torque |
Reluctance motor exhibits relatively lesser torque at the start. |
Induction motors provide larger starting torque as compared to reluctance motor. |
Cost |
Reluctance motors are less costly. |
Induction motors are expensive than reluctance motors. |
Variable speed |
Reluctance motors are better suited for variable speed applications due to their precise speed control. |
Induction motors are not suitable for variable speed applications, as they require complex speed control mechanisms. |
Conclusion
Reluctance motors are suitable for applications where precise speed control is required. On the other hand, induction motors are available with lesser speed control and are well-suited for industrial and home appliances like conveyors, pumps and mixers.
Induction motors have short-circuited rotor winding and a stator winding to pass electric current to create a magnetic field for rotational speed creation. Reluctance motors utilize magnetic reluctance to develop a rotational force.
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