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What are the Different Types of Electric Motors?

By John Sunshine
Updated May 17, 2024
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Electric motors can generally be divided into several types: alternating current (AC) motors, direct current (DC) motors, and universal motors. A DC motor will not run when supplied with AC current, nor will an AC motor run with DC current; a universal motor will run with either AC or DC current. AC motors are further subdivided into single phase and three phase motors. Single phase AC electrical supply is what is typically supplied in a home. Three phase electrical power is commonly only available in a factory setting.

DC motors are also split into types. These include brush motors, brushless motors, and stepper motors. Of these types, brush motors are by far the most common. They are easy to build and very cost effective. Their major drawback is that they use carbon brushes to transfer electrical current to the rotating part, and these brushes wear over time and eventually result in the failure of the electric motor. The DC brushless motor eliminates the brushes, but is more costly and requires much more complicated drive electronics to operate.

A stepper motor is a special type of brushless motor that is used primarily in automation systems. A stepper motor uses a special type of construction that allows a computerized control system to "step" the rotation of the motor. This is very important when controlling a robotic arm. For instance, when you wish to move a specific distance as directed by a procedure in a program on the computer, a stepper motor may be the best choice.

Universal motors tend to have many features in common with DC motors, particularly brush motors. Also called series-wound motors, they are most commonly found in household appliances that run very fast for a short period of time. Food processors, blenders, and vacuum cleaners all often operate with universal motors.

Electric motors are usually sized in horsepower. The most common sizes are what are called fractional horsepower motors, i.e. 1/2 horsepower or 1/4 horsepower. Larger motors are typically only found in factories, where they can range in size to thousands of horsepower.

Electric motors also come with various speed ratings. Speed is usually specified as rotations per minute (RPM) at no load condition. As the motor is loaded down, the speed will slow down. If the motor is loaded too heavily, the motor shaft will stop. This is known as the stall speed and should be avoided.

Before you order an electric motor, you should determine the mounting type you require, the start up torque, the type of enclosure required, and the type of shaft output required. There are many choices in each of these categories. Hopefully, you just need to replace an existing motor that has failed and the salesperson can help you find a direct replacement. Otherwise, specifying the correct electric motor can be a daunting task.

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By anon308650 — On Dec 11, 2012

The starting torque should be posted on the name plate of the motor you are inquiring about.

By anon304589 — On Nov 20, 2012

What is the difference between a "S" type and a "KH" type AC motor?

By anon304049 — On Nov 18, 2012

The starting torque of a squirrel cage rotor is low, whereas the slip ring rotor is high.

By cherry — On May 13, 2012

Why does a tube light running on a.c. glow continuously even if the current is bidirectional?

By anon157750 — On Mar 04, 2011

what i cdf? Is it applicable to single phase motors? If yes how?

By anon129515 — On Nov 23, 2010

Motors are very simple. I will use a 3 phase AC single speed for example. The core of a motor is a shaft. The shaft is actually is what is excited by the windings to cause movement. There are three sets of windings each made of copper wire wrapped one on top of the other with a wax paper between each set so they are separated.

Then there is the housing of the motor. There are six wires on the top of the motor. U1 V1 W1, U2 V2 W2. Depending on how you connect them it will be delta or wye. By placing the bars across U2 to V2 and V2 to W2 in the terminal lug of the motor it will be in delta. U1 to U2, V1 to V2, and W1 to W2 will be wye. There is other ways to wire these such as start delta run wye, but these are the most common where I work.

By anon129514 — On Nov 23, 2010

Hopefully I can be of some assistance. Torque is determined by T = (Hp/RPM) * 63,025 <-the constant. 1Hp is equal to 746Watts. So start up torque would depend on the current draw when starting the motor. Usually in a motor that is a high torque motor it is Start Delta Run Wye. Thus not as hard on the motor or the breaker because Wye pulls so much current.

By anon125611 — On Nov 10, 2010

please answer my question: what are the different parts of electric motor, please?

By anon64407 — On Feb 07, 2010

does the dc motor burn when started on no load, because of mere short circuiting or is there a different reason?

By anon63327 — On Feb 01, 2010

Tell me the inner construction of all types of motors and generators.

By anon60759 — On Jan 15, 2010

It depends on the design designation of the motor. A, B, C or D.

By anon36162 — On Jul 10, 2009

lol who knows this answer?

By anon30799 — On Apr 24, 2009

What is starting torque of a motor?

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