Reversing Single Phase Motor

[hooverdale]

What will be the easiest way to reverse the rotation of a single phase cap start/ cap run electric motor without blowing any capacitor or burning the motor? I attached here the wiring diagram.

Regards,

Hoover

 

[Skogsgurra]

Could be impossible with that motor.

Only if auxiliary and main windings are *exactly equal*, it could be possible. The trick then is to switch windings. Disconnect wires from right-end sides of windings and reconnect with main and auxiliary windings switched.

But, if the auxiliary winding is different from the main winding, which is almost always true, you can't do it. You will certainly fry the auxiliary winding.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

Either the main or the start winding must be reversed but not both. The point where the main winding and the start (aux) winding join the yellow wire must be accessible to do this. If not, then see Gunnar's post. There are motors that have both windings equal but the ones that I have seen don't have a centrifugal switch and the start capacitor stays in the circuit when the motor is running. These are generally small motors used for valve or damper operation or to drive switch trains such as On load Tap Changers.
If you can't access the point where the yellow wire joins the main and the start winding you are probably out of luck.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

In ideal scenario you have 2 windings effectively 90 degrees apart in space and an impedance difference which also makes the associated currents and fluxes ideally 90 degrees apart in time. In that case you can reverse the polarity of one winding relative to the other and you reversed direction.

The real motor may not be quite so ideal, so I can understand why Gunnar mentions the possibility this might work.

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(2B)+(2B)' ?

 

[electricpete]

You could give it a try and check that the motor starts properl and runs with normal current.

=====================================
(2B)+(2B)' ?

 

[Skogsgurra]

I wasn't quite sure about the relationship between auxiliary and main winding if you switch polarity of the main winding. Mostly because of the dual paths through two capacitors to the auxiliary winding.

On second thought, I agree that it is probably be a good idea to change yellow and black wires of the main winding.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[burnt2x]

The simplest is to reverse the tapping of the main winding alone since you have the caps on the auxiliary winding.

 

[waross]

It doesn't matter which winding you reverse. The motor does not know the difference. But, just reverse the winding, not the capacitor connections.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[hooverdale]

Thank you all for the inputs. We did tried to reverse any of the two windings and yes we're out of luck. Main winding end (Black Wire) connected to running capacitor can be accessed but the other end can not.Connection was hidden inside a mica tube and tied against the winding.

It did run in reverse but it was too slow and noisy when we connect the main winding end (black wire) to the blue wire between the starting capacitor and centrifugal switch.


Regards,

Hoover

 

[dArsonval]

hooverdale asks:
"What will be the easiest way to reverse the rotation of a single phase cap start/ cap run electric motor without blowing any capacitor or burning the motor? I attached here the wiring diagram."

Most all single phase motors are reversed at the Start Winding. Or in the case of the drawing, "auxiliary winding".

A Double Pole, Double Throw toggle switch connected as shown in the wonderfully illustrated drawing attached will reverse the motor.

Once the motor has started and come up to full speed, the motor's internal centrifugal switch disconnects the auxiliary winding.
Hence, the motor will only reverse after it has been shut off and allowed to slow enough to actuate the internal switch again.

John

 

[waross]

That mica tube may be a thermal fuse. (Yes, I know, all fuses may be referred to as thermal. But for the protection of small motors a fuse that is rated at the temperature at which it will open may be used instead of a current rated fuse.)
A possibility;
As I understand it, you have two wires going into one end of the tube and the yellow winding coming out of the other end.
If you cut one of the wires going into the end of the tube, you will have one end of one winding. Use a multi-meter to see which one it is and then reconnect in reverse.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Compositepro]

I have done just as dArsonval shows in his drawing, which is pretty much what everyone has said, in order to make a number of pieces of equipment reversible. You will have to cut wires and lacings to access the ends of the windings and probably solder some extensions on the wires. This is not difficult. You just have to decide if it is worth your time and if you feel you have the skill. While you have the end off the motor you can drill a hole for mounting the reversing switch on the motor. Very convenient.