Change 120v Motor Rotation

Thread Starter

rivera2419

Joined Aug 14, 2020
2
I was given a working 120v electric motor however, the rotation is counter clockwise. The motor was manufactured in Mexico and I've been unable to find any information online. I know that some motors cannot have their rotation changed but I'm at a loss to know if this motor is non-reversible. If it is reversible, how can I get it to rotate clockwise?
 

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MaxHeadRoom

Joined Jul 18, 2013
21,405
Are any of those leads going to a Capacitor?
Measure the leads/connections going into the motor itself.
I could well be a PSC motor which generall means both windings are the same, which is this is the case, a simple SPDT switch can be used to reverse.
A second look I see it is a dual voltage motor.
Max.
 

shortbus

Joined Sep 30, 2009
7,930
Even the so called non-reversible motors can be modified to run in reverse. But it takes going inside the motor and changing the wire connections. I've done it, but can't think of an easy way to explain how to do it.
 

LesJones

Joined Jan 8, 2017
2,696
I notice from the information plate that this is a dual voltage motor. This makes it a bit more difficult to trace the windings. Are the screw terminals the supply input ? Which wires connect to the capacitor ?

Les.
 

MisterBill2

Joined Jan 23, 2018
7,000
Here is a suggestion to see how the windings are arranged and see just what you have. You will need to use an ohm meter to determine what wires go to which ends of which wires.
But before doing anything, verify that the motor runs on the voltage you chose and draws about the coreect amount of current at full load, or near full load.
THEN, write down what wires connect to what terminals. It is vital to get that right. Then measure resistances so that we can know what windings connect to which wires and terminals. A dual voltage motor may have four windings, that can be connected in series for the high voltage or parallel for the low voltage. You will also need to inspect and see where the capacitor connections are made. And you will need to know if the motor has a starter switch. Measure both the wires and between the connection pins, and also the 2 line connection posts.Then let us know.
 

LesJones

Joined Jan 8, 2017
2,696
Some dual voltage motors may only have three windings. The start (Or auxiliary winding.) is rated for the lower voltage setting. When the motor is configured for the higher voltage the two main windings in series are used like an auto transformer. The lower voltage required for the auxiliary winding is obtained from one of the two main windings. (This only works when the high to low voltage ratio is 2:1)

Les.
 

MisterBill2

Joined Jan 23, 2018
7,000
Some dual voltage motors may only have three windings. The start (Or auxiliary winding.) is rated for the lower voltage setting. When the motor is configured for the higher voltage the two main windings in series are used like an auto transformer. The lower voltage required for the auxiliary winding is obtained from one of the two main windings. (This only works when the high to low voltage ratio is 2:1)

Les.
OK, Les, I had neglected to consider that. Still, knowing what wires are associated with each winding would allow some to tell which pair could be reversed to reverse the rotation. And that was the reason that I suggested checking the resistance between leads.
On a few motors I have seen the connection diagrams on the underside of the terminal cover plate. Has the TS looked there?
 

shortbus

Joined Sep 30, 2009
7,930
OK, Les, I had neglected to consider that. Still, knowing what wires are associated with each winding would allow some to tell which pair could be reversed to reverse the rotation. And that was the reason that I suggested checking the resistance between leads.
On a few motors I have seen the connection diagrams on the underside of the terminal cover plate. Has the TS looked there?
On motors THAT ARE REVERSIBLE that will work. But some motors state that they are NOT reversible, and changing wiring at just the terminals does nothing, nothing at all to the rotation. That type motor can only be reversed by changes made internally to the windings.
 

MisterBill2

Joined Jan 23, 2018
7,000
On motors THAT ARE REVERSIBLE that will work. But some motors state that they are NOT reversible, and changing wiring at just the terminals does nothing, nothing at all to the rotation. That type motor can only be reversed by changes made internally to the windings.
certainly that is true, but without knowing what connections are available it is not possible to know.
 

MaxHeadRoom

Joined Jul 18, 2013
21,405
As a rule, up to 1/2hp capacity, as the one shown is, it is common to have the run and start windings equal, which makes it very simple to change direction externally. As each winding can be start or run.
Where the windings are separate size, and the common connection is internal, then it is virtually committed to a uni-directional motor.
For this size of motor, it most likely is a PSC motor, no start winding switch.
Max.
 
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