Motor rotation reversal

[jburgess]

Motors in question are 120 volt 1-phase and apparently they were rotating correctly at one point in time and later they appeared to be operating in reverse rotation. Could a phase change by the power company cause this? Any suggestions? There are about 350 motors on the system. Can a 120 volt motor operate in reverse rotation by switching the leads?

Jack Burgess

 

[Ed MacLaren]

Re: Motor rotation reversal

General purpose single-phase motors cannot be reversed by phase sequence changes or by interchanging the supply leads.

Here are the five basic types of single-phase motors, and the method of reversal.

Capacitor-start - Interchange the start winding (5 and 8)leads.

Split-phase - Interchange the start winding (5 and 8)leads.

Shaded-pole - Disassemble and reverse the rotor (end-for-end).

Series - Interchange the armature (A1 and A2)leads.

(Obsolete)Repulsion-induction - Reposition the brush holder.

There may be new types of motors that I'm not familiar with.

Are you sure these aren't three phase motors?

Ed

 

[jburgess]

Re: Motor rotation reversal

Thanks for the quick reply, The motors are 1-phase 120 volt. You gave me the info I needed.

 

[charlie]

Re: Motor rotation reversal

FYI, there is nothing an electric utility can do to reverse the rotation on a single phase motor. Three phase, that is another story.

 

[Guest]

Re: Motor rotation reversal

Hey ed there are also some motors out there where the leads are not numbered but rather are color coded.in most cases where color coding is used you change the red and black. I always check the red and black in these case where I dont have a diagram to make sure that red and black lite out to each othe and not back to the run. In other words are they a single circuit? In that case with a 6 lead single phase motor the highest probability is that its the start winding.The best thing to have of course is a diagram on the nameplate or a diagram inside the cover of the j box. Then if you can read its a snap!