Reversing a single phase motor

[psno]

I have a customer who wants to reverse a single phase, capacitor start motor with a drum switch. So far, when I've tried different wirings, the motor continues to run in the same direction (even though it came to a complete stop). The motor wiring is for 115V, 4 leads, with the drum switch having 4 leads. Any ideas?

 

[jbartos]

Suggestion: Visit

http://www.engr.usask.ca/classes/ABE/312/labs/labnine2002.pdf

for speed reversal. Reverse the starting winding leads, contact the motor manufacturer tech support

 

[SteveKW]

What are the leads labeled out of the motor, nameplate information and drum switch specs?

 

[edison123]

psno,

Unless both ends of the start and run windings are brought out, you cannot reverse the direction of rotation. Normally they are not brought out, since most of the single phase motors have one direction driven equipments.

As jb says, if you can open the motor and create access to both ends of the start winding, then you can reverse the direction by changing the input leads.

 

[Dopler]

Reversing the start winding that is connected to a centrifugal device.

 

[busbar]

There is another important safety consequence of attempting to reverse a cap-start motor. Consider while normally running, a motor with a centrifugal-start switch is reconnected for reverse operation via drum switch or reversing starter. Unless there is adequate “coastdown” time for the motor's centrifugal switch to reclose, the motor will continue running in the original direction {!} and indeed, not reverse as might be expected.

This can be especially embarrassing if the driven load is an opening/closing gear train on a multi-ton steel door; where the requested 3ø motor would need another week’s time for delivery.

 

[jbartos]

Suggestion: If the motor happen to have an arrow indicating the direction of rotation, then the change of the motor direction of rotation should be done under a manufacturer tech support supervision, e.g. motor may or may not be cooled properly, internal design of teeth is for one direction only, etc.

 

[aolalde]

psno:

If you have terminals T1,T4 and T5,T8 for a NEMA capacitor start motor , just reverse the line connection of T5 and T8 (starting winding).

If you do not have those terminal leads, you have to disassembly the motor and identify the starting winding leads, then reverse the polarity connection. Check that the cooling fans are radial type (bidirectional)