What is a 3-Phase Motor and How Does it Work?
Three-phase motors (also annotated numerically as 3-phase motors) are widely used in industry and have become the workhorse of many mechanical and electromechanical systems because of their relative simplicity, proven reliability, and long service life. Three-phase motors are one example of a type of induction motor, also known as an asynchronous motor, that operates using the principals of electromagnetic induction. While there are also single-phase induction motors available, those types of induction motors are used less frequently in industrial applications but are widely used in domestic applications such as in vacuum cleaners, refrigerator compressors, and air conditioners, owing to the use of single-phase AC power in homes and offices. In this article, we will discuss what a three-phase motor is and describe how it operates. To access other resources about motors, consult one of our other motor guides covering AC motors, DC motors, Induction motors, or the more general article on the types of motors. A full list of related motor articles is found in the section on related articles.
To understand single phase motor, it is useful to first understand three-phase power.
In electrical power generation, alternating current (AC) that is created by a generator has the characteristic that its amplitude and direction changes with time. If shown graphically with the amplitude on the y-axis and time on the x-axis, the relationship between the voltage or current vs. time would resemble a sine wave as shown below:
Electrical power carried to homes is single-phase, meaning that there is one current-carrying conductor plus a neutral connection and a ground connection. In three-phase power, which is used in industrial and commercial settings to run larger machinery that has greater power needs, there are three conductors of electrical current, each of which is operating at a phase difference of 120o of 2π/3 radians apart. If viewed graphically, each phase would appear as a separate sine wave, which then combines as shown in the image below:
