Dual voltage single phase reversible motor wiring

[Yankeefarmer]

Yesterday I helped my wife’s uncle hook up a Jet metal lathe he had just purchased. Had to inspect the motor terminal wiring to determine whether it was wired for 120 vac or 240. After determining that it was wired up for 240 vac, I got it connected and working- except it rotates backward when started using the Fwd button. I told him to operate it using the Rev button until I could figure out how to correct the problem. This is the first time in my 67 years of life I have encountered a single phase reversible motor, so I‘m hoping someone here with experience can check my conclusions and advise whether my diagnosis is correct.

I’m attaching two photos. One is the nameplate on the motor, and the second is the terminal wiring.Based on these, I believe that what happened is the person who originally wired it for 240 failed to remove the red wire from the center terminal and replace it with the black wire which you can see has been taped up and disconnected. But I’m confused as to why the motor nameplate has a “B“ next to the line on the lower left of the 120 volt diagram. There are no visible numbers near any of the motor terminal studs.

 

[htmdude57]

Can you just swap the wires from the REV button to the FOR button?

 

[fitter30]

Post the whole tag brand and model of motor and lathe

 

[Zeke]

This is a long thread but the answer is there.

 

[Yankeefarmer]

Can you just swap the wires from the REV button to the FOR button?

The wiring to the switch buttons is very inaccessible. As it was, I had to remove the motor from lathe just to remove the terminal cover.

 

[American Locomotive]

The "B" is there, because the red wire isn't supposed to go all the way to the motor. It's supposed to go to that junction at the switch, and a black wire is supposed to go from the motor, to that point at the switch. But they probably realized at some point that having two black wires was a bad idea, so they made it red all the way down but never updated the diagram.

 

[Yankeefarmer]

Post the whole tag brand and model of motor and lathe

I can do that later this week when I go back to check on his progress. He‘s 88 years old and building a Cushman utility cart powered by a supercharged and turbocharged Buick V6 with a sprint car front end and 9” Ford rear. When I took the photos I posted, I only did it for record purposes “in case.” We didn’t know at the time there would be a control issue.

 

[Yankeefarmer]

This is a long thread but the answer is there.

Thanks. I‘ll read through it.

 

[Yankeefarmer]

The "B" is there, because the red wire isn't supposed to go all the way to the motor. It's supposed to go to that junction at the switch, and a black wire is supposed to go from the motor, to that point at the switch. But they probably realized at some point that having two black wires was a bad idea, so they made it red all the way down but never updated the diagram.

Thank you. That is a very logical explanation for what I’m seeing and confirms my diagnosis of the problem and the way to fix it.

 

[American Locomotive]

Don't change any wires until you see what's going on in the switch.

 

[Yankeefarmer]

Don't change any wires until you see what's going on in the switch.

Ok. I probably won’t ever be making any changes, because he is happy knowing if he pushes a certain button, regardless of what it’s labeled, the lathe will turn and he can machine the part he needs to. I doubt he’ll want to pull any part of the machine apart again if he knows he can make chips with it. He just wants to get that Cushman built.

 

[TractorJeff]

At 88, I agree with him!

 

[Yankeefarmer]

I want to thank everyone who helped me in this thread. Last night, I finally figured out how the switch connections worked, and were consistent with the typical motor wiring diagram that @Bert had provided to @Zeke in the thread that Zeke linked to. These confirmed my diagnosis of what likely caused the backwards rotation that existed and how to fix it.

This morning, I went back to see him and the lathe and explained what likely had happened and how to fix it. He doesn’t want to change it over because he’d rather be machining the parts he needs for his build, and he can’t actually read the “FWD” and “REV” letters on the buttons anyway. Hers happy knowing that pressing the bottom button starts it in the direction he needs. While there, I got the exact model number of the lathe, and was able to find a manual for it on the web. The manual includes instructions for wiring it for 240vac and those instructions agree with the diagram on the motor and my analysis!