Electric Motor

In the early 1800s, Micheal Faraday was bringing out the aspects and utilization of electricity. 

The electric motor, in general, is well known as a motor, is one of the biggest advancements witnessed in the scientific field. The life we are leading today is because of the invention of the motors, or else we would be using electricity just to light the bulb. The electrical motor is a device that converts electrical energy into mechanical energy. In simple terms, the electrical motor is a device used for producing rotational energy.

Working Principle of Electric Motor

The electric motor works on the principle that when a coil is placed in the magnetic field and the current passes through it resulting in rotation of the coil. 

Working of the Electric Motor

Now let us start with the working of the electric motor. The schematic representation of the electric motor is as shown below.

Before we understand how it works let’s have a look at the parts of the electric motor. The basic design of the electric motor consists of a rectangular wire, two strong magnets, and a battery. If we are asked what are the two main components of an electric motor then the answer would be the magnets to produce the magnetic field and the coil to exhibit the effect of the magnetic field.

Parts of the Electric Motor

• A rectangular coil ABCD.

• Two strong magnets, that can be of any type either it is a horseshoe magnet or the bar magnets. They are used to provide a strong magnetic field.

• Split rings are used to rotate the rectangular coil.

• The brushes are used as the contact between the split rings.

Working

• Now, when the electric current is passed through the rectangular coil ABCD. We notice that the current between BC and AD arm are parallel to the magnetic field, whereas the current between AB and CD is perpendicular to the magnetic field. Therefore the magnetic field will only act upon the AB and CD arms. 

• From Fleming’s left-hand rule, in the AB arm, the direction of force is downwards and the magnetic field is from north to south. Similarly, in the CD arm, the direction of force is upward.

• Therefore, the forces in the AB and CD arm are in opposite directions, this will result in the rotation of the rectangular coil ABCD.

• After half rotation, the ring Q will come in contact with the brush X and ring P in contact with the Y, this will lead to a change in direction of the current. 

• Since the direction of the current is changed, the direction of forces in the arm AB and CD will also change, hence the coil continues to rotate in the same direction.

After studying about the motors the usual question arises is what are the uses of electric motors. Electric motors are used widely in most of the appliances such as they are used in fans, mixers, etc.

Uses of Electric Motors

• They are used in electric fans.

• They are used in washing machines.

• Used in water pumps.

Types of Electric Motors

The three primary types of electric motors are DC motors, AC motors and other special purposes motors.

Below are listed the subtypes and explanations of DC, AC and Special purpose motors:

(A) DC Motor: The electric motor that is used to convert the direct electrical current into mechanical work is called a DC motor. The different types of DC motors include DC shunt motor, separately excited motor, series motor, PMDC motor and compound motor.

1. DC shunt motor- Similar to the armature windings and field windings, the windings of the DC shunt motor are linked parallelly; this parallel linkage is called a shunt and the winding is called shunt winding.

2. Separately excited motor- In this type of motor the armature windings are made stronger to generate more flux and the connection between stator and rotor is built by using different power supplies. The separately excited motor is controlled from a stunt.

3. DC Series motor- the rotor windings in this type of motor are connected in a series. The DC series motor operates on the simple law of electromagnetism. The electromagnetic law states that in order to produce an electromotive force an electromagnetic field is brought into interaction with an electric circuit. The electromagnetic law results in the rotational motion of the motor. This type of motor is majorly used in cars or elevators as starter motors.

4. PMDC motor- PMDC motor or permanent magnet DC motor comes with an inbuilt magnet which is permanently placed inside the motor. This magnet ensures the formation of the magnetic field which is extremely necessary for the operation of the electric motor.  

5. DC compound motor- DC compound motor is the fusion of the DC series motor and DC shunt motor. Since both the series and shunt are present in this motor, the start and rotor are connected to one another through the compound of series and shunt winding.

(B) AC motor: AC in the AC motor stands for alternating current, that is used for its working. This type of motor usually consists of an outer and inner part; the outside stator is made out of coils through which alternative charge or current is passed to produce rotation in the magnetic field. Whereas the inside rotor part is connected to the output shaft that generates a second magnetic field in rotation. The two main types of AC motor are synchronous motor and induction motor.

Following are the explanations of the working of the two types of AC motor:

1. Induction motor- Induction motor is the type of AC motor which runs on non-synchronous speed; that is why it is also called asynchronous motor. This motor applies electromagnetic induction to convert electrical energy to mechanical movement of the motor. There are two types of induction motors that exist- squirrel cage motor and phase wound motor.

2. Synchronous motor- The synchronous motor works on the three-phase supply. The stator generates the rotating field current on which the rotor’s workings also depends. When the accuracy of the rotation is very high these types of motors can be used in robotics and automation.

(C) Special Purpose Motor: Simply, the special purpose motors include all the other types of motors other than the general-purpose AC motors and DC motors. Some of the widely used special purpose motors are stepper motor, brushless dc motor, hysteresis motor and reluctance motors.

Following are the explanations of the workings of these special purpose motors:

1. Stepper motor- An efficient alternative to stable revolution is the step angle revolution, that can be provided by stepper motors. We are aware that the rotation angle of any rotor is 180 degrees. In stepper motors, however, this rotation angle is divided into a number of steps like 9 steps of 20 degrees. Some applications of stepper motors include generators, plotters, fabrication of circuit and process control tools.

2. Brushless DC motor- The reason behind the innovation of brushless DC motors is to achieve high quality performance with less space occupancy. These types of motors are smaller than the AC motors. The absence of the commutator and slip ring is filled by implanting a controller within the stepper motor.

3. Hysteresis motor- Hysteresis motor has the most unique operation out of all the motors. It is a synchronous motor in which the rotational force in the rotor is obtained with the use of hysteresis and eddy current. The movement in the rotor is achieved by the stator winding's rotating flux.

4. Reluctance motor- This type of motor is the one phase synchronous motor and are usually applied signal generators and recorders. The auxiliary winding provides a stable speed to the motor.

Did You Know?

The electric generators are the equipment that works in the opposite way. Electric generators produce electricity by rotation.