How to Wire a Single Phase AC Motor

Written by karleigh spears
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How to Wire a Single Phase AC Motor
There are several styles of single phase motors, and the wiring depends on the particular type of motor. (motor.jpg image by Aussiebloke from

There are a number of different types of single pole motors, depending on the needs of the application. The wiring will vary according to the type of motor. The most common types are shaded pole, permanent split capacitor and the split phase motor. They are all designed for a particular use. The different types of motors are generally not interchangeable. The main difference is in the starting requirements and the run load.

Skill level:

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Things you need

  • Voltmeter
  • Screwdriver

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  1. 1

    Turn off the power and check with a voltmeter before attempting to wire a motor. A shaded pole motor has a weak starting torque---such as a ceiling fan, a fan in a refrigerator or a normal home fan---used to circulate air. This type of motor has two wires and a ground. The black (hot wire) goes to the switch. The white wire is the neutral wire. The bare or green wire is grounded to the screw on the case of the unit. These are normally 120 volts.

  2. 2

    Wiring a split phase motor, or a capacitor start motor, requires the use of a relay. There is a start winding and a run winding. The terminal for the start winding will lead to the start relay. The start relay will disconnect the start circuit when the motor reaches about 80 per cent of its speed. This circuit gives the motor an extra kick to start.

  3. 3

    Wiring a permanent split capacitor uses a run capacitor that stays engaged full time. There is still a run and start winding, but there is not a relay involved. The red wire (start terminal) will lead to the capacitor; the black (run terminal) wire will lead to the line voltage (switch, relay). The white wire will lead to the common line on a 120-volt system or to the other side of the starting device.

Tips and warnings

  • When replacing a motor, it is recommended to replace the capacitor.

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