Wire an Electric Motor

Electric motors are used in a wide variety of applications that affect our daily lives. Electric motors are the tools that use the alternating current (AC) power supplied to your home or shop by the power distribution company and transform it to mechanical energy to drive compressors, fans, tools, washing machines, garage door openers, and anything else that requires mechanical motion to operate. AC power is available in either three phase, or as single phase split neutral. The single phase AC has two legs, at 120 volts AC when referred to an electrical neutral, but 180 electrical degrees out of phase with each other. Ground is different from the electrical neutral, and is provided only for protection from electric shock. THE PURPOSE OF THE GROUND WIRE IS TO BLOW THE FUSE IN CASE SOMETHING SHORTS TO THE CASE.The fuse protects the motor from overload and possibly fire, while the ground wire protects you from shock by forcing the fuse to blow. Smaller motors are generally wired as 1 phase to neutral, providing them with single phase AC power. Larger motors are generally wired as 3 phase AC motors, using all 3 phases of incoming power and not connecting to the electrical neutral line. In addition, direct current (DC) motors can be used in battery power applications that do not have AC. All of these types of motors must be wired properly to perform the desired motion, and all are wired differently. Use these tips to learn how to wire an electric motor.

Steps

Connect a DC Motor

1. Check the voltage rating of the motor. The rated operating voltage will be listed on the nameplate of the motor. For example, a motor intended to run from a 12-volt car battery should be rated at 12 volts.
2. Determine the rotation. The motor faceplate will define which direction, clockwise or counterclockwise, the motor shaft will turn when the 2 motor wires are connected to the power source. The motor nameplate or manufacturer's information will specify which of the 2 motor wires should be connected to the positive side of the power source and which should be connected to the negative side of the power source to achieve the desired direction of rotation.
3. Wire the power source to the 2 motor leads as indicated. The motor should rotate in the desired direction. If for some reason the motor rotates in the opposite direction than desired, reverse the motor by swapping the connections of the 2 motor leads.

Install a Single Phase AC Motor

1. Find an appropriate power connection point. This should be where the power distribution wires enter the building. The house or shop will have single phase 120 volts AC and single phase 240 volts AC. Very few houses will have 3 phase power 120 volts AC is suitable for most household uses. 240 volts AC is used for heavy home equipment and in shops. Check the nameplate of the motor to determine which voltage is needed.
2. Determine if the motor is a single phase or a 3 phase motor. In addition to being noted on the motor nameplate, this should be obvious as single phase motors have 2 wires(usually + gnd), and 3 phase motors have 3 wires(+gnd). For this application, a 2-wire single phase motor is needed.
3. Establish the direction of motor rotation. Consult the motor nameplate or manufacturer's information for this information. That information should direct that 1 motor wire be attached to 1 (any 1) of the 3 power phases available and the other motor wire be attached to electrical neutral.
   • Count the single phase motors being driven by the 3 phase input power in a line to neutral configuration. Attempt to balance the loads from each of the 3 available phases so that the neutral line is carrying as little current as possible. A high neutral current can unbalance the power system and cause poor motor performance.
4. Wire the motor. Use wire strippers, available at hardware or electrical supply stores, to strip about half an inch (13 mm) of insulation from the end of the motor wire. Secure the motor wire under the screw termination available on the power distribution panel. Confirm that the motor rotates in the proper direction. If the motor does not rotate in the desired direction, the input leads may NOT be swapped to reverse the motor direction of rotation.See the face plate. How to reverse rotation varies among motor manufacturers.

Connect a 3 Phase AC Motor

1. Confirm that the motor is a 3 phase AC motor. This information will be on the motor faceplate. It also can be noted that the motor has 3 connecting wires(+ gnd), rather than 2. Confirm from the motor faceplate the operating voltage that the motor will require from the power distribution system.
2. Figure out the direction that the motor will turn. The motor nameplate and motor manufacturer's information should explain the needed wiring to make the motor turn in a particular direction.
3. Attach the motor power leads. Wire the 3 motor leads to the 3 phases of input power. Do not use the neutral line. If the motor does not turn in the desired direction, swap any 2 of the 3 motor wires to reverse the direction of rotation of the motor.

Warnings

• Lethal voltages exist on the power distribution panel (the breaker box). Make sure that the master system circuit breaker is turned off before wiring a motor.

Things You'll Need

• Wire strippers

Sources and Citations

• http://industrial.panasonic.com/ww/i_e/25000/fa_ctlg_sgeard_shing_e/fa_ctlg_sgeard_shing_e/controller_e_5.pdf
• http://www.electricmotorwarehouse.com/motor_connection_diagrams.htm
• http://sawdustmaking.com/ELECTRIC%20MOTORS/electricmotors.html

See also

• Wire an Amp to a Sub and Head Unit
• Terminate a Patch Panel
• Forward Your Home Phone to a Cell Phone
• Splice Wire
• Wire a Double Switch
• Organize and Hide Your Hanging Computer Cables Under Your Desk
• Crimp Rj45
• Wire a Telephone
• Wire a Potentiometer
• Wire a Zone Valve

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What links here

• Check an Electric Motor