PDA

View Full Version : How to reverse motor rotation.



cuemaker
10-22-2009, 11:44 PM
I have an older motor.. it spins the wrong way...

Wierdscience gave me some advice to switch motor leads 5&8 to reverse the motor. Only problem is there are only 2 wires coming out of the motor......

What to do?

Edit to add: Of course there isnt an diagram either... When I look in the motor, there is a small circuit board, but thats it..

camdigger
10-22-2009, 11:52 PM
I have an older motor.. it spins the wrong way...

Wierdscience gave me some advice to switch motor leads 5&8 to reverse the motor. Only problem is there are only 2 wires coming out of the motor......

What to do?
Post a picture of the end of the motor the wires come out of and maybe any name plates on the motor, An overall picture of the motor would help too. All this is a PITA, but will help those of us not familiar with the situation to make some suggestions.

cuemaker
10-23-2009, 12:10 AM
http://i201.photobucket.com/albums/aa129/xringx/aircompressor014.jpg
http://i201.photobucket.com/albums/aa129/xringx/aircompressor016.jpg
http://i201.photobucket.com/albums/aa129/xringx/aircompressor009.jpg
http://i201.photobucket.com/albums/aa129/xringx/aircompressor012.jpg

cuemaker
10-23-2009, 12:12 AM
ummm, the motor has been cleaned by the way.....New NSK bearings also...used all those spring washers that you can see in one of the pics to press the bigger one in...rather lucky I had those handy...

Langanobob
10-23-2009, 12:26 AM
It will help if you open up the junction box on the side of the motor housing, where the cord goes in, and take a picture of the leads.

Also, the motor nameplate, which should also be on the housing. The picture you show with the two wires is the overload switch and reset button, not the motor leads.

J Tiers
10-23-2009, 12:45 AM
looks like a classic repulsion motor, unless it is actually DC......or universal....... several possibilities, which will look much the same.

is there any data plate on the motor?

I am assuming you would mention that it was DC if it was. So repulsion is most likely. Unless there is stuff on the end I can't see, does not look like repulsion-induction, but could be, since the shorting bars don't take up much space and might not be visible, and those are more common.

IIRC the rotation is reversed by shifting brushes , there may be a way to rotate them somewhat.

Also can be done in a repulsion type (not repulsion start-induction run)by re-connecting the rotor (changing brush connections) That can be done to plug-reverse.

cuemaker
10-23-2009, 12:47 AM
http://i201.photobucket.com/albums/aa129/xringx/aircompressor018.jpg
http://i201.photobucket.com/albums/aa129/xringx/aircompressor019.jpg
http://i201.photobucket.com/albums/aa129/xringx/aircompressor020.jpg
http://i201.photobucket.com/albums/aa129/xringx/aircompressor022.jpg

cuemaker
10-23-2009, 01:38 AM
IIRC the rotation is reversed by shifting brushes , there may be a way to rotate them somewhat.

Also can be done in a repulsion type (not repulsion start-induction run)by re-connecting the rotor (changing brush connections) That can be done to plug-reverse.

I can take out the thing holding the 4 things (i assume they are the brushes since they ride on the small copper part) and rebolt them into any of (4?) positions... in fact, while putting this thing back together i didnt bolt it in in the same position....

winchman
10-23-2009, 03:23 AM
That looks like a repulsion-induction motor. You should be able to change the direction of the motor by changing the position of the brushes with respect to the field poles.

Look at the picture showing the brush-holder (the third picture in post #3). The large poles of the stator are at the 0, 90, 180, and 270 degrees. The brushes are at (approximately) 35, 125, 215, and 305. If you shift the position of the brush mounting plate about 20 degrees clockwise so the brushes are at 55, 145, 235, and 325, the rotation should be reversed.

I can't tell for sure from the photo if the brush mounting plate can be moved to that position, but it looks like the clamps under the screws at 90 and 270 could be loosened to allow the plate to be moved.

The brushes short the armature to produce a torque at low speeds. The torque direction depends on the offset of the brushes with respect to the stator poles. Once running, it works like an induction motor.

Roger

dr pepper
10-23-2009, 03:38 AM
changing the brush holders postion will change the direction and speed of the motor, but you might find that tricky if its not deisned to do that.
It looks like there are just 2 wires comming from the stator (outer stationary windings), if you reverse the connections of those 2 wires then your rotation should reverse.
Brush motors are noisy critters, but give decent power for their size.

EVguru
10-23-2009, 06:28 AM
4 brushes and 4 clear field windings.

It's either a series or shunt wound motor. With both of them reversing the polarity of the field also reverses the polarity of the armature so they continue to run in the same direction. You can power them from both AC and DC.

Given the low rpm rating, it's almost certainly shunt wound, which unlike series has a more or less linear rpm per volt characteristic.

As has been said, reverse the field in relation to the armature to reverse rotation, but you'll also need to reset the brush angle.

If you look at the picture showing the brushes and field coils, you'll see that the brushes don't quite line up with the point at which the field coils butt up against each other. That's the timing angle (just like ignition timing) and you would need to set the timing to the other side of the gap. The motor would run without doing this, but the speed/torque/efficiency would be different.

Once you've reversed the motor, run it no load for a few hours to reseat the brushes.

J Tiers
10-23-2009, 09:53 AM
4 brushes and 4 clear field windings.

It's either a series or shunt wound motor. With both of them reversing the polarity of the field also reverses the polarity of the armature so they continue to run in the same direction. You can power them from both AC and DC.

Given the low rpm rating, it's almost certainly shunt wound, which unlike series has a more or less linear rpm per volt characteristic.


Look at dataplate..... 1750RPM AC.... That means it is NOT a DC shunt or series motor...


The big copper ring indicates a repulsion start induction run motor. At speed, it should be moved by a system of weights and levers inside the hub to short the end of the commutator bars ("copper ring things")....

The brush position should adjust to change direction. IIRC the direction should adjust LESS than 90 deg to do it, and should adjust in the direction you want the motor to turn. The angle is since that is a 4 brush motor, and a 90 deg movement would likely only reproduce the same conditions as now.

Since it runs as an induction motor, the start direction determines the run direction,. That 1750 RPM is also typical of an induction motor.


I found a decent reference, although it shows a 2 pole motor.

http://books.google.com/books?id=CxQdC6xPFSwC&pg=PA88&lpg=PA88&dq=%22repulsion+start+motor%22&source=bl&ots=jjhRYecq0T&sig=Ml6cggK6HqNhVcAlkI1Rtc1SBps&hl=en&ei=pqbhSobRLpSsMI334bwB&sa=X&oi=book_result&ct=result&resnum=6&ved=0CBYQ6AEwBQ#v=onepage&q=%22repulsion%20start%20motor%22&f=false

J. R. Williams
10-23-2009, 10:16 AM
The unit is a typical repulsion start- induction run motor. The brush holder assembly can be rotated to reverse the direction of rotation. The view of the brush holder unit shows an indent mark on the top side of the unit. Loosen the two clamp screws and rotate the assembly to line up with another index mark on the end bell casting. The rotor has one winding that is much darker than the others indicating a possible bad connection at a commutator bar of internal short. The commutator need to be cleaned up.
This type of motor is great for hard starting systems.

JRW

winchman
10-23-2009, 10:45 AM
"The view of the brush holder unit shows an indent mark on the top side of the unit."

Good observation!! I missed the mark, but what you suggest agrees with what I thought might work.

Roger

cuemaker
10-24-2009, 10:00 AM
Guys, could it be as easy as this?? Take a look at this new pic....

At the top where the 2 bolts are, is a plate with a finger... on the round plate that holds the brush, are 2 slots... I currently have the finger in in the right most slot.

Is it enough movement to go from one slot to the other in order to reverse the direction?

AND, i am not asking if this current config is right, as I intend to put it back into the condition it was when I took that earlier pic, and then shift it to see if it moves it right...

But over all, just moving the brushes that little much sound right?

Thanks all!!!! you have been a big help in teaching me new things.

http://i201.photobucket.com/albums/aa129/xringx/aircompressor002-2.jpg

winchman
10-24-2009, 10:22 AM
Moving the plate so the finger is in the other slot will change the rotation.

Since I now what to look for, I can see the plate in the earlier picture. The finger doesn't show up well in that end view, though.

Roger

cuemaker
10-24-2009, 10:24 AM
Moving the plate so the finger is in the other slot will change the rotation.

Since I now what to look for, I can see the plate in the earlier picture. The finger doesn't show up well in that end view, though.

Roger

I agree,,, but based on what I know and what I see in the 1st pic...it was in the right slot..

I will play with it and compare....

Thanks!!!

J Tiers
10-24-2009, 10:50 AM
Yes it should be.

That picture would have been useful earlier...... the brush plate was not very visible in the earlier pics, and it looked fixed in position.....

If you look at the latest picture, you can clearly see that adjacent brush pairs are connected together. The left//upper, and the right/lower. That corresponds to adjacent poles being opposite polarity, making it like the linked diagram in my earlier post.

because the poles are close, the needed movement is relatively little.

Halfway between the positions will be a location that gives zero starting torque, but a lot of rotor current. Shifted to eaiter side are positions that give a bit less rotor current, but which give it in such a way that torque is produced on the rotor vs the stator poles...

cuemaker
10-24-2009, 11:21 AM
Mr Tiers...

No clue what you just said.. but glad you agree on the small movement...

In regards to your info... Torque....This little motor runs a 2 stage compressor... I think I need the torque more than anything else...agree?

When I have it in position, I will post a good pic...

Yes, I wish I had known that the last pic was the one I needed to get info faster...but its always the last one/last place you get to when hunting for something

cuemaker
10-24-2009, 02:31 PM
we are spinning correctly now!!

thanks guys! Hope to return the favor 1 day