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Old November 13th, 2007, 06:53 AM   #1
smcmanus
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Reverse Rotation on 120VAC Motor

Can anyone help me. I need to be able to Reverse a Single Phase 120VAC motor.
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Old November 13th, 2007, 07:54 AM   #2
jrwb4gbm
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If the motor has a starting capacitor on it, there should be some leads marked T5 and T8. Swap these two wires. If they are not numbered,they may be color coded. There could (should) be a legend plate on the motor to identify which two leads to change. Look inside the wiring junction box also for information. If it doesn't have a starting capacitor, you may need to take it to a motor rewind shop to get it changed. In some instances, you can change ends of one of the windings internally to do this.
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Old November 13th, 2007, 09:47 AM   #3
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Basically I need this motor to be able to run forward and reverse all the time. So if the motor does have a starting capacitor am I able to wire a motor starter relay for forward and reverse.
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Old November 13th, 2007, 09:51 AM   #4
TConnolly
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Yes, if it has a starting capacitor you can wire forward and reverse relays. The capacitor is switched out of the circuit once the motor is started.

If the motor uses a shaded pole instead of a capacitor then you are probably out of luck, you will need to replace the motor with a reversible one.
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Old November 13th, 2007, 10:20 AM   #5
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Look at these:
http://www.lmphotonics.com/single_phase_m.htm

http://www.patchn.com/motor_connections.htm
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Old November 13th, 2007, 10:26 AM   #6
Electrically_Bound
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I know that some motors have a centrifugal switch that disconnects the start capacitor once it rotates past a certain speed. While it may be possible to wire the start capacitor for forward and reverse, I'm thinking that you may have to go to a stop before reversing directions.
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Old November 13th, 2007, 10:38 AM   #7
Thomas Sullens
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I'm thinking that you may have to go to a stop before reversing directions.
U r right the motor has 2 at lease slow down until the governor kicks back in then it will reverse. This puts the start winding back into the circuit.
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Old November 13th, 2007, 01:13 PM   #8
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On any across line motor I would let it come to complete stop before reversing. The other thing to consider is heating and possible burnout of the motor as a result of frequent starting and stopping. If you are reversing every 10 second I doubt that motor will last long. If every 5 minutes it should be no problem.

Dan Bentler
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Old November 15th, 2007, 10:22 AM   #9
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Another option would be to use an A.C. drive that will accept 120 VAC single phase in and give a three phase output, such as these from Automation Direct. http://web1.automationdirect.com/adc...alog/AC_Drives

With this option you would gain the ability to ramp up/down, as well as vary the speed. On the down side you would have to change your motor to a three phase motor.

Hope this helps.
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