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How Does an Electric Motor Work?

Summary

Did you know that your home could have more than fifty electric motors all hidden inside the simple gadgets you use? Incredibly, little is known about these important accessories found in power tools and home appliances. In this article, we […]

Did you know that your home could have more than fifty electric motors all hidden inside the simple gadgets you use? Incredibly, little is known about these important accessories found in power tools and home appliances.

In this article, we explore the parts of an electric motor and how it works.

What Is an Electric Motor?

An electric motor is a device responsible for converting electric energy into mechanical energy. Its working is opposite to a generator that transforms mechanical energy into electricity.

Nearly every electronic appliance that generates mechanical movement when operating has an electric motor. Some appliances that contain motors include blenders, fans, dough mixers, refrigerators, dryers, washing machines, air conditioners, disk drives, power tools, hybrid cars, and electric vehicles.

Parts of an Electric Motor

A motor has different working parts that provide a power supply and coordinate rotational movement as desired.

Parts of an Electric Motor

Source: Engineering Projects

Below are the main parts of a simple electric motor:

Power Terminal

It is the main source of electromotive force that enables electric current to flow into the system

Commutator

Located at the far end of the coil is the commutator which is a metal ring split into two parts. Whenever the coil achieves half a rotation, the commutator changes the direction of the electric current inside the coil. Thus, both ends of the coils move in the same direction and the axle spins continuously.

 

Rotor/Armature 

The rotor is the component of the motor that delivers mechanical movement to the shaft and all the accessories attached to it. The rotor fits inside the stator and contains a set of copper wires winding around an axle.

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The rotor enables the spinning of the axle. As a result of the flow of electric current into the coil, a magnetic field is created which pushes into the stator’s magnetic field. This allows the axle to spin.

Brushes

They are connected to both terminals of the source of power, to allow the flow of electric power to the commutator. Brushes are made of graphite and exist on the opposite end where the rotor leaves the casing.

Field Magnet/Stator

It is the magnetic stationary part that creates an electromagnetic field around it. Different stators may have varying configurations but stators are permanent magnets or consist of magnet rows that surround the lower edge of the motor casing. To reduce energy losses, the stator has thin metal laminations on its core.

How an Electric Motor Works

Most electric motors operate under the principle of electromagnetic induction in which an electric current flowing through a wire wounded over a magnet creates an electric field. As a result of the electromagnetic field created, a force is generated that turns a motor shaft, causing it to spin.

An Explanation of Electromagnetic Induction by Khan Academy:

https://www.khanacademy.org/science/in-in-class10th-physics/in-in-magnetic-effects-of-electric-current/electromagnetic-induction/v/electromagnetic-induction-faradays-experiments

In a simplified explanation, electric current can flow through any wire that is a good conductor of electricity. When electricity flows through the wire, it creates a strong magnetic field. If you pass the wire in form of a coil around an iron rod, a magnetic field is created around the rod. Since the rod has two opposing poles, the addition of other magnets near the road will cause a continuous spinning motion.

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Therefore in an electric motor, current passes through the coil which becomes magnetized since it is wound around the magnet. With the coil attached to one end of the shaft and still suspended over a magnetic field, the magnetic forces on the other end of the shaft produce a force strong enough to spin the shaft.

YouTube explanation: How a DC Electric Motor Works

Source: Brilliant.org

Types of Electric Motors

There are two main types of electric motors namely Direct current (DC) motors and Alternating current (AC) motors. Although motors can run on both direct current and alternating current, AC-powered motors are commonly used because they require little maintenance.

 

DC Motor

It was the first type of motor used before the AC motor. The best thing about a DC motor is that you can control the speed by regulating the amount of power supply. They come in a wide variety of voltages, the most common being the 12V and the 24V. They are commonly found in small electronic appliances, hoists, lifts, and electric vehicles.

Advantages of DC Motors

  • They have a higher starting torque
  • Wide range of speed settings
  • Easy to install
  • Have the ability for quick start-up, acceleration, or reversing

Image of a DC motor

Source: Research Gate

AC motors

They offer a lot of flexibility in operation compared to DC motors. They also have varying speed drives and are easy to maintain.

Advantages of AC Motors

  • You can control the rate of acceleration
  • Have an adjustable limit of torque
  • They require little power on startup
  • Operational speed is adjustable
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Image of an AC Motor

Source: Instrumentation Forum

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