Can this single phase 120v motor's direction of rotation be reversed?

[Tomc938]

I'm trying to fix a 1" belt sander and need to reverse the direction of a motor I have.

I THINK this one can be reversed. I did one similar a couple of years ago, but can't remember what I did. I also can't get to the one I rewired to see if I can figure out what I did the first time.

Is there anyone who knows enough to tell me what needs to be done?

The lines in connect one to the upper connection, and one to the lower.

One wire from the motor connects to the middle contact and the other one connects to the top contact.

Part of me thinks I need to switch the motor wire from the post it is connected to to the post with the white wire, but I'm allergic to smoke.

Any thoughts would be appreciated. Correct answers will be evermore appreciated. ;o)

 

[jcdammeyer]

It's all about changing the direction of the current in the starting winding.

 

[Susquatch]

Not all single phase motors can be reversed. Those that can usually have more wires in the connection box than that.

As you know, I'm allergic to YouTube. I quit watching that one when I saw it used contactors.

Most single phase motors have several run windings. They are usually reversed by changing which run winding is connected to the start winding. But you don't have enough wires in there to be able to do that.

For those that only have one winding, you just reverse the polarity of either the run windings OR the start windings. Again, you don't appear to have enough wires there to do that.

All that said, you should try to find a wiring diagram for your motor. Some motors use other ways to do that and you never know.

 

[slow-poke]

FYI, I reversed a non reversible motor a while ago. One of the starter winding leads was not available in the junction box, so I opened the motor to get access to the windings were the pigtails are connected and was able to get access to the missing lead, took all of about 15 minutes.

 

[Susquatch]

One of the starter winding leads was not available in the junction box, so I opened the motor to get access to the windings were the pigtails are connected and was able to get access to the missing lead, took all of about 15 minutes.

Sometimes you can do that in the capacitor box too. But you know what you are doing. I'm leary of advising @Tomc938 to try that. What do you think?

 

[CWret]

but I'm allergic to smoke.

Me too. Electrical wiring and I have never played well together.
Smoke can be a startling result but not as bad as a shocking result.

 

[slow-poke]

Sometimes you can do that in the capacitor box too. But you know what you are doing. I'm leary of advising @Tomc938 to try that. What do you think?

I don't know, everyone has a different level of "take it apart" adventurousness. I'm often surprised how some people dive into unknown things with reckless abandon while others are afraid to make left hand turns.

In my case it was either reverse the unreversable motor that I had or buy one. For the 15 minutes it took, it was worth it.

 

[Johnwa]

There may be enough connections but it’s a big MAYBE. Power in goes to the top and bottom terminals. They COULD have hidden connections behind the insulating plate. The reversible winding would then be the two black leads coming from the interior of the motor.

 

[CWret]

I’ve got a history of taking things apart that i shouldn’t have.
Having a few leftover pieces after reassembling something is kinda normal.
I did a valve job on my first car (1960 Morris Minor). After putting everything back together my older brother came in the garage. He said “that was a good idea to get a new head gasket”. But I hadn’t, and the old one was still on the bench.

 

[jorogi]

Sometimes you can do that in the capacitor box too. But you know what you are doing. I'm leary of advising @Tomc938 to try that. What do you think?

Oh I think you're far enough away if it does go bang.

 

[mbond]

It is hard to tell very much from this photo, but I think some things are clear

1) the power input has a black and a white. Probably that's 120V single phase with hot and neutral
2) there are two output (towards the motor) terminals. One is connected to hot in, and the other is connected to nothing. presumably, it would be connected if the input was 220V single phase. But one of the wires could be a tie
3) at least some of the connections have been made with the wrong twist - tightening the nut draws the wire into the terminal if it is wound clockwise, but expels it when wound the other way.
4) stranded aluminum wire is in use

do those things make sense to you?

For single phase AC induction, the direction of rotation depends on the angle between the start and run winding. 3-phase motors are easy to change direction, but single phase motors have to have windings in the right locations to make that possible. I think that many (most? all?) do as they are mass produced on a line, and then leads that aren't needed for a particular model are just abandoned in the case

to find out if you can reverse this motor, you'll have to open the case and look at the windings I think

 

[Tomc938]

It is hard to tell very much from this photo, but I think some things are clear

1) the power input has a black and a white. Probably that's 120V single phase with hot and neutral
2) there are two output (towards the motor) terminals. One is connected to hot in, and the other is connected to nothing. presumably, it would be connected if the input was 220V single phase. But one of the wires could be a tie
3) at least some of the connections have been made with the wrong twist - tightening the nut draws the wire into the terminal if it is wound clockwise, but expels it when wound the other way.
4) stranded aluminum wire is in use

do those things make sense to you?

For single phase AC induction, the direction of rotation depends on the angle between the start and run winding. 3-phase motors are easy to change direction, but single phase motors have to have windings in the right locations to make that possible. I think that many (most? all?) do as they are mass produced on a line, and then leads that aren't needed for a particular model are just abandoned in the case

to find out if you can reverse this motor, you'll have to open the case and look at the windings I think

Yeah, It's not the best picture, and as I don't remember where I got if from, I don't know who left the ends in the wrong direction for tightening the nuts.

On the positive side, there is no Al wiring. Whoever did it tinned the ends with solder.

I'll be keeping my eyes out for a motor that runs in the right direction.

 

[Susquatch]

I'll be keeping my eyes out for a motor that runs in the right direction.

If you end up deciding to take one of mine, just tell me which way you want it to turn and I'll prewire it for you. As a bonus, I think most of mine are dual voltage.

 

[Ironman]

I have reversed a 3hp non-reversible motor. The ends of the start winding were buried in the main windings and it was truly not reversible as stated on the label. So I took the end bells off and planned to just flip the stator end for end. They got me there too. The stator and iron core were not centered in the housing, so I measured the offset. So I made a piece of pipe that would just slip between the winding and the shell and rest on the iron core, had to machine a bit off the O.D. I put it in the hydraulic press and pushed the core about an inch to put the offset where it needed to be when I flipped over the stator housing.
There were four welds from the shell to the stator, but they popped easily and when I had it where I wanted I zapped them from the holes in the shell.
I reassembled it with the stator flipped opposite to what it was, and now I had a clockwise motor.
I call it the Brute Force reversal method.

 

[Susquatch]

Wow Tom,

I did a Kijiji search in your area as far south as Victoria. NOTHING! There were motors for $50 but not what you want

In my area, there are dozens of what you want at that price.

Makes me wonder what makes things so different......

Maybe your salvage guys just don't advertise? Perhaps you should just check around for salvage outfits and electric repair shops. That's where the bulk of motors around here are at. Ya, there are a few being sold by guys like us, but most seem to be available through junk collectors.

 

[mbond]

I have reversed a 3hp non-reversible motor. The ends of the start winding were buried in the main windings and it was truly not reversible as stated on the label. So I took the end bells off and planned to just flip the stator end for end. They got me there too. The stator and iron core were not centered in the housing, so I measured the offset. So I made a piece of pipe that would just slip between the winding and the shell and rest on the iron core, had to machine a bit off the O.D. I put it in the hydraulic press and pushed the core about an inch to put the offset where it needed to be when I flipped over the stator housing.
There were four welds from the shell to the stator, but they popped easily and when I had it where I wanted I zapped them from the holes in the shell.
I reassembled it with the stator flipped opposite to what it was, and now I had a clockwise motor.
I call it the Brute Force reversal method.

that is another way of reversing!

 

[Tomc938]

Wow Tom,

I did a Kijiji search in your area as far south as Victoria. NOTHING! There were motors for $50 but not what you want

In my area, there are dozens of what you want at that price.

Makes me wonder what makes things so different......

Maybe your salvage guys just don't advertise? Perhaps you should just check around for salvage outfits and electric repair shops. That's where the bulk of motors around here are at. Ya, there are a few being sold by guys like us, but most seem to be available through junk collectors.

I know! And machinery is even fewer and further between.

Even at our Restore they want $30-50 for a 1/4 motor - like what you would find in a dryer.

Another way to reverse a motor is to disconnect the started windings. Then when you turn it on you give it a little spin in the direction you want it to spin and away she goes! (But I'd rather not if I don't have to)

I'm going to start keeping an eye out for free dryers. It would be worth picking on up and hauling it to the scrap metal bin on the off chance the motor is still good.

 

[jcdammeyer]

I know! And machinery is even fewer and further between.

Even at our Restore they want $30-50 for a 1/4 motor - like what you would find in a dryer.

Another way to reverse a motor is to disconnect the started windings. Then when you turn it on you give it a little spin in the direction you want it to spin and away she goes! (But I'd rather not if I don't have to)

I'm going to start keeping an eye out for free dryers. It would be worth picking on up and hauling it to the scrap metal bin on the off chance the motor is still good.

What HP are you looking for? What direction should it turn if you are looking at it from the shaft end. Many years ago I bought some motors from PA for the various Gingery Projects. Only built the hack saw. Lathe has a different sealed motor. Can't get at them until tomorrow during the day to even know what I have here.

 

[Tomc938]

What HP are you looking for? What direction should it turn if you are looking at it from the shaft end. Many years ago I bought some motors from PA for the various Gingery Projects. Only built the hack saw. Lathe has a different sealed motor. Can't get at them until tomorrow during the day to even know what I have here.

It's just for a 1" belt sander. Harbour Freight style.

1/4 horse or so would be perfect. 1/2" shaft and CCW.

 

[jcdammeyer]

It's just for a 1" belt sander. Harbour Freight style.

1/4 horse or so would be perfect. 1/2

I'll look tomorrow!