What is Electric Motor?

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Electric motor is a most widely used electrical machine in a wide range of applications from domestic to industrial. It is a type of electromechanical energy conversion device that transforms electrical energy into mechanical energy. The principle of electromechanical energy conversion was given by Michael Faraday in 1821.

This article is meant for explaining the basics of electric motor, such as definition, construction, working, types, etc. So, lets get started with the basic introduction to electric motor.

What is an Electric Motor?

An electromechanical energy conversion device that transforms electrical energy into mechanical energy is called an electric motor.

Therefore, an electric motor takes electricity as the input and produces mechanical energy in the form of rotation of shaft as the output.

The block diagram of an electric motor is depicted in the following figure.

An electric motor is one of simplest mean for producing mechanical power from electrical power.

Electric motors are commonly used to drive mechanical loads like fans, pumps, compressors, conveyors, lifts, cranes, air conditioners, and more.

Construction of Electric Motor

In actual practice, we have different types of electric motors having different constructions. But all the electric motors have the same fundamental structure.

A typical electric motor has two essential parts namely, stator and rotor.

The stator is a stationary or non-moving part of the motor. While, the rotor is a moving or rotating part of the motor.

The stator has a winding called stator winding. The stator also provides the mechanical covering and protection against mechanical threats to the internal parts of the motor. The stator of an electric motor is basically a hollow cylinder made up of cast iron.

The rotor of the electric motor is a moving part having a rotor core, rotor winding, and a mechanical shaft. The rotor core is a cylindrical piece of steel provides housing to the rotor winding. The rotor core is mounted on the shaft and a mechanical load is attached to the motor shaft.

Apart from stator and rotor, an electric motor also has some auxiliary parts such as bearings to reduce friction between moving and stationary parts, cooling fans to balance the temperature of the motor, etc.

Let us now understand how does an electric motor work.

Working of Electric Motor

An electric motor works on the principle of electromechanical energy conversion through electromagnetic induction.

In an electric motor, there are two windings namely, field winding and armature winding. The placement of these windings depends on type of design of the motor. For example, in an induction motor the field winding is placed on stator, while in a synchronous motor, the field winding is placed on the rotor. But the functions of these two windings remain the same in all types of motors.

The field winding produces the working magnetic flux in the motor while the armature winding develops the torque required to drive the mechanical load connected to the shaft.

When electrical energy is input to the electric motor, a magnetic field is produced in the air gap between the stator and rotor. This magnetic field cuts the armature winding and induces an emf and a current in the armature winding through the electromagnetic induction. Due to current in the armature winding, a magnetic flux is produced.

Now, there are two magnetic fields inside the motor namely, main field and armature field. These two magnetic fields interact with each other and produces a torque that rotates the rotor.

This is how an electric motor works when an electrical input is given to it.

Classification of Electric Motors

Electric motors are broadly classified into the following two types

DC Motor

An electric motor that takes direct current electricity to work and produce mechanical energy output is called a DC motor or direct current motor.

AC Motor

An electric motor that requires alternating current electric supply to operate and produce mechanical energy output is called an AC motor or alternating current motor.

Types of Electric Motors

Based on power supply, electric motors can be classified into the following two types

• DC Motor (Direct Current Motor)
• AC Motor (Alternating Current Motor)

The dc motors are further classified into the following major types

• Permanent Magnet DC Motor
• Separately Excited DC Motor
• DC Series Motor
• DC Shunt Motor
• DC Compound Motor

The ac motors are classified into the following major types

• Single-Phase Induction Motor
• Three-Phase Induction Motor
• Synchronous Motor

There are some special types of electric motors used in practical applications, they are

• BLDC (Brushless Direct Current) Motor
• Hysteresis Motor
• Reluctance Motor
• Universal Motor
• Repulsion Motor

Let us now discuss practical applications of each of these electric motors.

Applications of Permanent Magnet DC Motor

A permanent magnet dc motor is a one which has permanent magnetic poles in its magnetic field system. This type of dc motor is used in the low power applications. Some practical applications of permanent magnet dc motors are given below

• Printers, computer memories, CPU fans, etc.
• Automobile wipers, windows, etc.
• Electronic toys.
• Portable vacuum cleaners.
• Camera lenses.
• Portable tools like trimmers, drills, etc.

Applications of Separately Excited DC Motor

A separately excited DC motor is a type of dc motor which has a field winding excited from a separate DC power supply. This type of dc motor is used in the following applications

• In electric trains and automatic traction systems.
• In actuators.
• In special industrial applications.
• Rolling machines.
• Paper machines, etc.

Applications of DC Series Motor

A dc series motor is one in which the field winding is connected in series with the armature winding. Hence, in dc series motors, the field winding carries equal current to the armature winding and thus produces a high starting torque.

DC series motors are used in applications where high starting torque and variable speed is required. Some common applications of dc series motors in practice are as follows

• Cranes and hoists
• Lifts
• Electric trains and vehicles
• Vacuum cleaners
• Hair driers
• Air compressors
• Electric hammers, etc.

Applications of DC Shunt Motor

A dc shunt motor has a field winding connected in parallel to the armature winding and receives full supply voltage. Since the voltage across shunt field winding is constant. Hence, DC shunt motors are considered constant speed motors.

The dc shunt motors are widely used in the following practical applications

• Blowers and fans
• Printers
• Centrifugal pumps
• Lathe machines
• Elevators, etc.

Applications of DC Compound Motor

A dc compound motor is one which has both series field winding and shunt field winding to produce the working magnetic field in the machine. Therefore, this type of dc motor exhibits characteristics of both dc series and shunt motors.

The dc compound motors are used in the following applications

• Rolling mills
• Electric drives used for conveyor belt
• Elevators
• Compressors
• Electric presses, etc.

Applications of 1-Phase Induction Motor

Single-phase induction motor is a type of alternating current motor that works on single-phase ac supply. These motors are designed to operate light loads used in domestic, commercial, or industrial applications. Some examples of practical applications of single-phase induction motor are listed below

• Pumps
• Fans and coolers
• Flour mills
• Compressors
• Grinders, and other low power appliances.

Applications of 3-Phase Induction Motor

A three-phase induction motor is an electric motor that requires three-phase supply to operate. It is a most widely used electric motor in industries. These motors are generally used to drive heavy loads and machinery.

A list of some common practical applications of three-phase induction motors is given below

• Large pumps
• Large compressors, fans, blowers, etc.
• Crushers
• Rolling mills
• Large flour mills
• Textile mills
• Paper mills
• Modern electric trains and vehicles
• Lifts and cranes
• Heavy industrial machinery, etc.

Applications of Synchronous Motor

Synchronous motor is a type of alternating current motor that runs at a constant speed called synchronous speed. The speed of a synchronous motor always remains independent of the load condition on the shaft.

Synchronous motors are widely used in the following applications

• Drive heavy mechanical loads at constant speeds.
• To drive ball mills, rod mills, in industries.
• In paper mills and cement mills.
• In power plant to improve power factor, etc.

Applications of BLDC Motor

BLDC (Brushless Direct Current) motor is a specially designed dc motor does not have carbon brushes to make connection between moving and stationary components. Since these motors have brushless construction, hence they require less frequent maintenance.

The BLDC motors are commonly used in the following practical applications

• Modern fans
• Electric vehicles
• Power steering of vehicles
• Lab equipment
• Robotics and automation systems
• Hard disk drives
• Medical surgical tools, etc.

Applications of Hysteresis Motor

Hysteresis motor is a special type of synchronous motor which utilizes the hysteresis phenomenon to operate. It is basically a type of synchronous motor. It provides a silent and constant speed operation.

Some practical applications of hysteresis motors are given below

• Sound recording and producing devices
• Timing devices
• Compressors and pumps
• Electric clocks
• Tape printers
• Indicating instruments, etc.

Applications of Reluctance Motor

Reluctance motor is a special electric motor which operates on the principle of magnetic reluctance. It consists of a salient pole rotor and a stator similar to the induction motor. In the reluctance motor, the torque is produced in the rotor due to reluctance i.e., the rotor tends to align itself in the position of minimum reluctance.

The following are some common applications of reluctance motors

• Electric vehicles
• Signaling and control equipment
• Electric clocks
• Recording instruments
• Teleprinters and gramophones
• Drill or lathe machines, etc.

Applications of Universal Motor

A specially design electric motor that can run on both AC and DC power supply is called a universal motor. It is also known as AC series motor as it has a field winding connected in series with the armature winding and commonly operates on AC supply.

Universal motors are used in applications where high starting torque is required. Some common applications of universal motors are given below

• Table fans
• Hair driers
• Mixer and grinders
• Portable power tools like drill machine, grinders, etc.
• Various electric appliances used in kitchen
• Blowers, etc.

Applications of Repulsion Motor

Repulsion motor is a type of ac motor which operates on the principle of repulsion between two magnetic fields of stator and rotor. It is a type of single-phase ac motor that provides a significantly high starting torque and good operating characteristics.

Reluctance motors are commonly used in the following applications

• High speed lifts and hoists
• Toys
• Coil winders
• Electric locomotives and vehicles
• Pumps
• Fans
• Machinery used in textile industries
• Printing presses, etc.

Advantages of Electric Motors

Electric motors offer several advantages over other methods of producing mechanical energy to drive mechanical loads. Some key benefits of using electric motors are given below

• Initial and operation costs of electric motors are low.
• Electric motors have relatively longer lifespan.
• Electric motors require less maintenance.
• Electric motors provide easy start and stop and efficient speed control.
• Electric motors have less noisy operation.
• The energy conversion efficiency of electric motors is relatively high.

Conclusion

In conclusion, electric motor is an essential electrical machine used to convert electrical energy into mechanical energy. A typical electric motor consists of two major parts namely stator and rotor. The working of an electric motor is based on the principle of electromechanical energy conversion through the electromagnetic induction. Electric motors are widely used in various applications like in fans, refrigerators, conveyors, crushers, electric vehicles, and more. In this detailed article on electric motor, I have explained the definition, construction, and working of electric motor.