Introduction
Electric motors are responsible for converting electrical energy into mechanical energy. It is an important device in the electronic and mechanical industry as it plays a vital role in constructing many electronic appliances, tools and machines. This article will be a beginner’s guide to the world of electric motors as it will look into the different types of electric motors, applications and much more.
What is Electric Motors?
Electric motors are devices that transform electrical energy into mechanical energy, usually using the electromagnetic principle. Most electric motors work through the interaction of the motor's magnetic field and electrical currents wound around a wire to generate force in the form of torque supplied on the motor shaft.
Electric motors can be driven by direct current (DC) supplies like rectifiers or batteries or by alternating current (AC) supplies such as electrical generators, power grids, or inverters. Electric motors can be classified based on their power supply type, construction, application, and type of movement output.
The Key Components of Electric Motors
The electric motor has different parts, but the key components are:
- Electric Motor Bearings: The rotor spins on its axis thanks to the support of bearings from the motor housing. The rotor spins on its axis thanks to the support of bearings from the motor housing.
- Electric Motor Rotor: The rotor is a component of the motor that moves and generates mechanical energy. It basically holds conductors that carry current, and the stator magnetic field applies a force to rotate the shaft.
However, other rotors have permanent magnets, and the stator holds the conductors. Permanent magnets provide high efficiency over a bigger power range and working speed.
The air gap between the rotor and the stator allows it to spin. The breath of the gap has an important effect on the motor’s electrical properties. It is usually made to be as small as possible, as a large gap can result in weak performance. Electric motors function with a low power factor primarily due to their design.
- Electric Motor Stator:The stator encircles the rotor and houses the field magnets. These magnets can be either electromagnets, which are made up of wound wires on an iron ferromagnetic core or permanent magnets. They generate a magnetic field that travels through the rotor winding, exerting force on it. The stator’s iron core comprises multiple thin metallic sheets with insulation, referred to as laminations. Laminations reduce energy loss, which occurs if a solid core is used.
- Electric Motor Armature: The armature is made of wound wire on a ferromagnetic core. When an electric current flows through a wire, it creates a magnetic field that exerts a Lorentz force on the wire, causing the rotor to rotate and supply mechanical output. Coils of wire are wrapped around a laminated iron core to create magnetic poles when supplied with current.
- Electric Motor Commutator: A commutator is a rotary switch that periodically reverses the current flow in the rotor winding as the shaft spins, supplying alternating or direct current to the rotor. It consists of a cylinder made of multiple metal contact sections on the armature. Electrical contacts known as brushes are utilised to transfer electric current to the rotor. These brushes are made of a soft conductor material, such as carbon, which is pressed onto the commutator. As the rotor spins, the brushes create sliding contacts with each consecutive section of the commutator, supplying current to the rotor. Additionally, the rotor wire windings are connected to the commutator sections.
Types of Electric Motors
There are several types of electric motors, and they all differ by how the conductors and the field are arranged and also by the control that can be exercised over mechanical outputs, torque, speed and position. Some of the major types of electric motors are discussed below.
- DC Motors
A DC motor is any rotary machine that converts electrical energy from direct current (DC) into mechanical energy. DC motors were commonly used as they can be powered by direct current lighting systems.DC motor speed can be controlled over a broad range by either a variable voltage supply or altering the current strength in its field winding.
Small DC motors are used in appliances like tools and toys, while large ones are used for the propulsion of elevators and hoists, electric vehicles, and drives for rolling mills for steel.
- AC Motors
An AC motor is an electric motor that operates on alternating current. It has an outer stator with coils that create a magnetic field. An inner rotor is attached to the shaft to create a second spinning magnetic field.
There are two primary types of AC motors: synchronous and induction motors. The induction or asynchronous motor solely relies on a little difference in speed between the speed of the rotor shaft and the stator spinning magnetic field called slip, which results in rotor current in the AC winding of the rotor.
- 12V Motors
A 12V DC motor is affordable and small but powerful enough to be used in many applications. 12V DC motors are usually brushless and can operate without using brushes to move the electrical current. A unique property of a 12V DC motor is its operating voltage.
- Stepper Motors
A stepper motor, also called a step motor, is an electromechanical device that converts electrical pulses into precise mechanical movements. A brushless DC motor divides a complete revolution into several equivalent steps. It is characterised by converting a series of input pulses square waves into accurately defined increments in the rotational position of the shaft.
A stepper motor comprises toothed electromagnets surrounding a central rotor, which is a gear-shaped iron piece. A microcontroller or an external driver circuit powers the electromagnets.
- Industrial Motors
Industrial electric motors convert electrical energy into mechanical power, producing rotary or linear force. Although DC currents power some industrial motors, they are often powered by alternating current (AC) supplies like power grids or generators.
The components of an industrial motor include the rotor, stator, coil, air gap, and commutator. Other types of motors you need to know are single-phase motors, servo motors, 3-phase motors, 2HP electric motors, 1HP electric motors, and brushless motors.
Applications of Electric Motors
Electric motors are mainly used in various applications such as fans and machine tools, pumps, alternators, power tools, movers, compressors, turbines, rolling mills, ships and paper mills.
The electric motor is important in various applications like high voltage AC heating, cooling and ventilating equipment, motor vehicles, and home appliances.
Standardised motors provide appropriate mechanical energy for industrial use. Applications include machine tools, power tools, industrial fans, blowers and pumps, household appliances, vehicles, and disk drivers.
Small motors are commonly used in electrical watches, while regenerative braking is often utilised in traction motors. Electric motors are used for regenerative braking in traction motors in reverse as generators that recover power that may otherwise be lost due to friction and heat.