Changing rotation on electric motor

The three horse motor on my compressor died. I've had this big 5.5 hp Marathon for just such an occasion. It is 230v 1ph 215T frame (if that matters).

I've downloaded Marathon's installation and operation manual. Under changing rotation, it says follow the diagram on the motor. Surprise, surprise. No diagram. All wires are numbered. It is currently running CW.

Any help from the gallery? I have new breakers! :)

--Andy Asberry--


Reply to
Andy Asberry
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On single phase motors you basically have two windings. One is the starting winding and the other is the running winding. *IF* there is a capacitor it will usually be in the running winding.

Anyway, check all your leads and let us know what they are. There is probably a number or letter on each of them. Someone can probably tell you from the numbers / letters you provide.

Now, to your question. Usually, all you have to do is reverse the two leads on the STARTING winding. That takes care of it. ;-) You just have to figure out which two are the right ones.

I'm assuming it is a single voltage and you have two groups of 3 wires, one being the electrical line feeding the other two. One running winding and one starting winding attach to each of the power lines. Again *if* you have numbers like S1 & S2 just switch those two. But I'm not sure what labels you'll have - if any.

Hope this helps.


Reply to
Al Patrick

SORRY. This statement is wrong.

*It will usually be in the STARTING WINDING*


Al Patrick wrote:

Reply to
Al Patrick

Could be inside the wiring box on the motor?

Reply to

Andy, If the motor is an induction motor and single phase, rotation often can be changed by reversing the armature end for end. This is especially true with centrifugally switched, shaded pole starting. Swapping the wires on the start capacitor will not change the start direction on capacitor start motors. Reversing single phase motors have two start windings, one for CW and one for CCW. Direction is determined which start winding is engaged with a switch. Motors that have only a single start winding can only be reversed by rotating the run field winding. This can only be done if the end plates are identical. Steve

Reply to
Steve Lusardi


If you do not have any of the leads labeled you can still reverse the rotation. Take an ohm meter (anything to check continuity) and determine which leads complete a circuit. On a single voltage motor you should only have four wires for the two windings.

In your case reverse either set of wires as it will effectively have reversed the other, electrically.


Reply to
Al Patrick

This advice has got a bit garbled.

Single phase SHADED pole motors have no accessible start windings (they are the short circuited copper rings). They are sometimes (rarely) fitted with two MAIN windings - one for each direction. The construction normally permits direction reversal by mechanical 180 deg rotation of the stator with no change of the rotor shaft connection to the load

If the rotor is reversed end for end and the drive taken from the previously unused rotor shaft end the drive direction will remain unaltered. This is also true for single and three phase induction motors.

Single phase motors with split phase or capacitor start have a main winding and a smaller start winding. Rotation can be reversed by reversing the connections to either (NOT both) the main or the start winding. Once the motor is up and running the start winding is no longer connected so running reversal is not possible.

A 5.5HP motor is almost certainly capacitor start or capacitor run. To reverse you need to identify the two ends of either the main winding or the start winding and reverse one of them. To sort this out we need more information - you need to post the existing connections to the numbered wires.


Reply to

It is *only* necessary for the shaded pole starting -- though I have move the shading rings on clock motors to make them run in reverse.

Agreed -- for the capacitor only.

*No*. At least not for single-phase motors of the horsepower range needed for machine tools.

For a dual-voltage motor, you have three windings (beware, the numbers which I have used to label the windings are for my convenience in describing it, and are not likely to be used on commercial motors):

(1) o-----WWWWWWWWWWWWWWW---------------o (2)

(3) o-----WWWWWWWWWWWWWWW---------------o (4) ___ (5) o-----WWWWWWWWWWWWWWW---)|-o o------o (6)

Windings (1-2), and (3-4) are the two run windings. winding (5-6) is the start winding -- with the centrifugal switch and the capacitor.

To run at the lower voltage, you connect (1), (3), (5), and (L1) together, and (2), (4), (6), and (L2) together.

To reverse it, you interchange where (5) and (6) are connected.

To run at the higher voltage, you connect:

(L1) to (1)

(L2) to (4)

(2) and (3) to (5)


To select one direction of rotation, you connect (6) to (L1) (1). To select the other direction of rotation, you connect (6) to (L2) and (4).

No! Only one start winding, two run windings, which are connected in parallel to run at the lower voltage, or in series to run at the higher voltage. The start winding is only designed for the lower voltage, but by connecting one end of it to the junction of the two run windings connected in series for high voltage operation, you have half the applied voltage available between that point and either end, and switching the free end of the start winding from one end to the other is equivalent to reversing it -- but needs fewer switch contacts to accomplish the task.

No -- as long as the start winding (with the capacitor and centrifugal switch) is brought out as its own independent wires, all that is needed is to reverse either the start winding or the run winding, assuming a single voltage motor.

And reversing the field can be awkward with a centrifugal switch, because part of it is mounted on one end of the rotor.

Enjoy, DoN.

Reply to
DoN. Nichols

T5 and T8 are the leads to the start winding that controls the direction of rotation.

Near the end of this article is the most of the information you're looking for. Look at the diagrams, read the trouble shooting section at the end.

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Reply to
GeoLane at PTD dot NET

It was the reversal of 5 and 8. Thanks to everyone.

This motor must weigh 200 pounds. Takes it a while to wind down.

--Andy Asberry--


Reply to
Andy Asberry

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