electric motor

[fobco]

hi,new to the forum,i need electrical help,i have a motor that spins the wrong way,i have taken in apart,and it has only two wires coming out,instead of the usual four or more,can it be reversed, :lol:

 

[Digit]

Brush or induction motor?

Roy.

 

[fobco]

hi digit,its a induction motor,far eastern,well made very heavy,this is a great forum,some top reading,its a shame my hero scrit,is no longer with us,he must be a hundred years old,the amount he knew about machines,anyway,there is still plenty of very clever people here,sorry for going on,but now i have started,i cant stop boring you all,thanks looking anyway...................frank.

 

[Digit]

Will this help?

http://answers.yahoo.com/question/index?qid=20080306131848AASRcve

Roy.

 

[RogerS]

hi digit,its a induction motor,far eastern,well made very heavy,this is a great forum,some top reading,its a shame my hero scrit,is no longer with us,he must be a hundred years old,the amount he knew about machines,anyway,there is still plenty of very clever people here,sorry for going on,but now i have started,i cant stop boring you all,thanks looking anyway...................frank.

Scrit can be found here

 

[Racers]

Hi,

Many years ago I striped down a small two wire induction motor and cleaned and lubed the bearings etc and reassembled it and it ran backwards I had assembled it with the stator (this bit http://www.geocities.com/vijayakumar777 ... nduct5.jpg) the wrong way round, So can you strip it down and reassemble it with the stator the opposite way round?

Pete

 

[mister henderson]

It may be a shaded pole motor, usually only quite small though. It's all to do with giving the motor a nudge in the required starting direction. Have you got the body of the motor the right way round? It's the part that wraps around the rotor.

 

[9fingers]

The answer is " not easily"
If you know what you are doing you might be able to find and separate the start and run windings and bring them out to get the more usual 4 wires. There is a risk that the winding will be damaged doing this.

As others have suggested it might be possible to flip the motor body end for end and modify the wiring to get back to the centrifugal switch but this need full symmetry of the stator and care.

Far better to get another reversible motor. These regularly come up on ebay.

Bob

 

[Digit]

Or can you mount the motor swung through 180 degrees horizontally?

Roy.

 

[jonny boy]

Hello, Sorry to sabotage the thread but while we are on the subject of motors, I have just bought a Dewalt mitre saw off ebay for £30 and the brushes are making far too many sparks, the saw will run when the trigger is depressed but something is definitely not right. Any ideas as to what may be causing the seriously exessive sparking?
cheers,
jonathan.

 

[OLD]

jonny boy
worn brushes or duff armature.

 

[9fingers]

Hello J-B,

Two possibilities. The brushes could be worn too short, jamming in their guides or have weak springs from overheating.
Easily replaced. should not be too dear.

The other possibility is that the armature is damaged. Not easy to test this on a home rig. There might be localised discolouration of the commutator between some segments and not others, which would indicate damage.
They are not repairable so you will need a new armature. likely to be at least what you paid for the saw. If everything else is sound then still possibly worth it. Buy new bushes at the same time anyway.

Bob

 

[jonny boy]

Thanks for the reply's. The brushes are still over half inch long and I can tell the saw hasn't seen serious use so i'm assuming it's not the brushes. The commuator was very black and I cleaned it up with a scouring pad to a shiny polished finish and tried it again but same as. Really exessive sparks and blackening of the commuator again! New armature?

jon.

 

[9fingers]

Reckon so. What is the model number?

Bob

 

[fobco]

hi chaps,thanks for all your replies,the stator as you call it,seems glued in,i have gave it a few thumps,but it will not budge,i tried reversing the bit in the middle,but the winding are tight,together one end,someone did say about the capacitator wires.

 

[jonny boy]

Bob, the saw is the DW 705, same as the 703 but with a 12 inch blade. It's been replaced with the DW706. The guy I bought it from say's he bought it two years ago and hardly used it. He did say that he left it outside one day when it started raining but it still worked OK for months after.
jon.

 

[9fingers]

One of several sources for DW spares
http://www.toolsandpartsdirect.co.uk

There seem to be a few variants of the 705 so I suggest you contact them with full serial number to make sure you get the right parts.

Make sure you are sitting down before you look at typical prices for armatures!!

Bob

 

[Digit]

Fobco, the motor can be reversed, but trying to explain over the net is a bit like trying to tell someone how to tie a tie, if you must reverse it I would suggest you pay to have it done.
You will not be able to remove the stator without possibly destroying it.

Jonny, you can test the armature if you have an OHM meter. Water will normally have little effect on a modern motor provided it's allowed to dry out before use.

Roy.

 

[jonny boy]

The best part of £100 for an armature!
There is I believe, something that electrical engineers can do with the commuator, I think they can skim off a layer in a special lathe to refresh it. I would just like to point out though, the brushes are really soft, you could easily scrape a gouge in them with your nail. The consistency of hard chalk, is this right?

jon.

 

[Digit]

Armatures can be skimmed but that is only appropriate if wear is the cause. If the insulation is 'gone' replacement is the only cure.

Roy.