Electric Motors and Their Efficiency: The Basics

An electric motor is a machine which converts electrical energy by generating force through torque on the motor shaft; to do this, the motor interacts between the magnetic field of the motor and the electric current in a wire winding. They obtain power through direct current (DC) sources like batteries or alternating current (AC) sources, such as generators and inverters. Since their creation, motors have become far more efficient through manufacturing breakthroughs.

Motors are classified using a number of considerations, including their construction, type of power source necessary for use, purpose, and type of motion output. Moreover, motors can be either brushed or brushless, air-cooled or liquid-cooled, and have one to three phases. They range from being conventional general-purpose motors to massive, 100 megawatt motors that are used to power ships, pipeline compression operations, and pumped-storage applications. Other mechanisms that use motors include power tools, household appliances, and industrial fans. Electric motors can even be used in reverse as generators in some instances.

Motors work by generating torque which is either linear or rotary force; this force is then used to move an internal mechanism like a fan or elevator. Many motors are constructed with the expectation of continuous movement over large distances. When compared to internal combustion engines (ICE), electric motors are more efficient, smaller, lighter, cheaper to build, and do not release carbon into the atmosphere. For these reasons, alongside others, combustion engines are being replaced by electric motors in large numbers. Although, they are heavy because of the weight of the battery which makes their use in vehicles difficult.

Electric motors are composed of two electrical components which move in relation to one another, and when combined, they generate a magnetic circuit. One component is on the stationary stator, and the other is located on the rotating rotor. Motors consist of the rotor, bearings, windings, stator, and commutator. As the moving part of the electric motor, the rotor begins the process by turning the shaft which helps to deliver mechanical power. The rotor is supported by the bearings, which allow it to rotate around the axis, and the bearings themselves are supported by the motor housing. Current-powered motors, in particular, feature windings, which are wires laid in coils that are wrapped around a soft iron magnetic core in order to create magnetic poles which constantly cycle. The stator is composed of field magnets; this component of the motor is stationary, and it creates a magnetic field that moves through the rotor and acts on the windings. Some motors also have a commutator connected to the rotor windings which sends electricity to the rotor. Every half turn of the commutator changes the direction of the current in the rotor windings to make sure the magnetic field of the stator puts out the same torque on the rotor.

In order to calculate a motor’s efficiency, one must divide the mechanical output power by the electrical input power. Peak efficiency happens at 75 percent of the rated motor load. For example, a 10-horsepower motor is at its most efficient while moving a 7.5-horsepower load. Around the world, countries have established regulations to enforce the use of more efficient electric motors. Additionally, it is known that larger motors tend to be more efficient than smaller ones.

Homeowners, manufacturers, and industries have the power to increase the efficiency of electric motors by performing one or more of the following procedures. One can use copper windings in stator coils to increase their conductivity and copper bars in the rotor to save electricity. This is because copper is more conductive than aluminum, a material which is not as efficient overall. Additionally, the rotors and stators of the motor should be made of high quality steel to minimize power loss and strong magnetic permeability. Finally, adding more coils will increase the magnetomotive force. All of these measures combined can help with the efficiency of an electric motor.

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