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How to Reverse an AC Single Phase Motor

Updated February 21, 2017

Alternating current (AC) single phase motor is an electromagnetic device that converts electrical energy into mechanical energy. The motor is based on the "electromagnetic induction" theory and has two magnets, one permanent and one induced. The permanent magnet is called the stator and the induced magnet is called the rotor that rotates inside the stator. The motor has two windings, namely "run" and "start". The direction of rotation of the motor depends upon the connections of these windings with respect to each other. You can reverse the direction of rotation of the motor by reversing the winding connections.

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  1. Turn off the electricity supply to the motor. If it has a plug, simply unplug it. If it is hard-wired into the electrical system, turn off the circuit breaker and remove the main fuse from the circuit.

  2. Locate the winding terminal box on the motor. Usually it is located on the top-end belly of the motor opposite to the rotating shaft. Refer to the motor schematic in the operating manual for exact location of the box.

  3. Unscrew the box cover with an appropriate screwdriver. If nuts are fastened on the cover, use a nut-driver of appropriate size to remove the nuts. Remove the box cover to expose the winding terminals.

  4. Locate the windings connected onto the terminals. Windings are usually coloured and number coded. Run windings are located on terminal T1 (blue), T2 (white), T3 (orange), and T4 (yellow). Start windings are located on terminal T5 (black), T6 (violet) and T8 (red).

  5. Unscrew the terminal T1 and T4 with the screwdriver or use the needle-nose pliers if push locks are installed. Pull out the wires. Remember the colour of the wires detached from the respective terminal -- write it down in case your forget.

  6. Connect the wires detached from terminal T1 to terminal T4.

  7. Connect the wires detached from terminal T4 to terminal T1.

  8. Fix the screws or the push locks back on the terminals with the screwdriver or the needle-nose pliers.

  9. Place the terminal cover back on the winding terminal box.

  10. Turn on the electricity supply to the motor through circuit breaker. Install the fuse back into the circuit.

  11. Run the motor and check the reversed direction of rotation.

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Things You'll Need

  • Motor's operating manual (if available)
  • Flat head screwdriver
  • Philips screwdriver
  • Nut-driver set
  • Needle-nose pliers

About the Author

Neha Tripathi

Neha Tripathi has been freelancing since 2006 for various websites. She is a certified Computer Software Developer from NAAC with additional certification from Energy Exchange for Technical Analysts, Bangalore. Neha has worked with integrated energy companies as a senior consultant. She holds a Master of Business Administration in oil and gas management.

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