Thread: Help with electric motor

Hi Kev,

Sounds like either the start winding or start cap has gone open cct.

Check the start winding for continuity, by unplugging the machine from the mains.

Measure resistance from AC live motor terminal, to the live terminal of the start cap.
You should get a low value.

Measure between the other terminal of the start cap to neutral, should be zero.

Regards
Ray

Thanks Ray Ill give it a shot.

Kev.

Hi

check also that the centrifugal switch contacts are clean and have a wiping action when activated. The moving contact should deflect the stationary contact slightly, or the moving contact blade bends slightly, contributing to the "contact wipe".

Clean the switch contacts with fine glasspaper, clean with metho, dry off, and check the switch action again by hand, or by running up the motor in the correct direction with a power drill.

May have intermittent start circuit wiring.

Are you sure that there are no additional wires which are meant to be used for a reverse mode?

Those capacitor specs look reversed in volts and capacitance, or suspect.
Probably should read 125 MFD 500V AC.

mike

Originally Posted by mike48

Hi

check also that the centrifugal switch contacts are clean and have a wiping action when activated. The moving contact should deflect the stationary contact slightly, or the moving contact blade bends slightly, contributing to the "contact wipe".

Clean the switch contacts with fine glasspaper, clean with metho, dry off, and check the switch action again by hand, or by running up the motor in the correct direction with a power drill.

May have intermittent start circuit wiring.

Are you sure that there are no additional wires which are meant to be used for a reverse mode?

Those capacitor specs look reversed in volts and capacitance, or suspect.
Probably should read 125 MFD 500V AC.

mike

Mike the text on the cap says Motor starting, Ac volts 120 , capacity 400mfd ,I replaced it with one that says 125 AC volts 400mfd

The throw out switch is working ok , the bush that slides along the shaft pushes on a wave / spring type washer that has a contact point on one side that is closed when the switch is activated by the rotation of the shaft .When it is in the relaxed position the contact is held open.
I had some images I took during the week but have deleted them .

I couldn't get a reading on the multimeter following Rays advice , I think my multimeter maybe fritzed too or its just me not knowing how to use a multimeter correctly .
I set the meter on OHM and tested the connections as per Rays instruction , all I got was 10000 mohm with the one flashing on the meter . It reads the same what ever I do with it.

Any way I put the motor back on and it won't start with a load with out some help .I started it twice and spun the spindle by hand to get it moving .The third time it would not spin and dropped the overload on my power socket board.
Id say Ray is correct and the start windings are fritzed .
I might take it to an electrical mob in town and see if they can investigate further and determine if it worth trying to fix. Otherwise I'm in a fix as I will have to get a replacement and I don't see H&F having any spares for this machine as it is of around 1979 manufacture.

Thanks for your input ,really appreciate it .
The whole Christmas break has been less than ordinary around here with electrical failures , first the washing machine , then an aircon , dishwasher ,now my my mill motor ,all in the same week actually.

Kev

My initial thoughts are the cap voltage is too low ( maybe the one you pulled off was not original) and/or the start winding is u/s.

Don't muck around take it to a qualified motor repairer, all the above information is wrong your motor will still run in reverse you have inadvertently reversed a connection somewhere besides if your insulation is cracking it would be worth having a qualifier repairer fit new tails to the windings and have the thing re-varnished and baked. But on the other hand if you want to electricute your self go ahead and keep doing what you are doing

Hmmm ...

Talking just about the electrotechnology aspects only...

You may have a motor designed with the start winding connected across half the run winding,
I had a Taiwanese drill press motor in 3/4 HP like this.
Can lead to reverse rotation, if the sense of windings is not correct after overhaul.

This may also explain why the cap voltage rating is 125 Vac.

Time for the experts.

Cheerio. mike

Hi,
I second the advice from Phil. They will be able to test each thing as they eliminate the one before.
It sounds to me the start circuit is not working at all,depending on where it stops with no load it will get away one way or the other or not at all with a load it needs more of a help so does not start.

On the subject of the capacitor voltage, it may not be wrong. Many motors are made with 2 115V run windings that are connected in parallel for 115V or series for 240V and only 1 115V start winding (with capacitor and contacts) which is in parallel with 1 run winding so that it always works with 115v.
FWIW
mike48's post was not there when I typed this but he is saying virtually the same thing about the capacitor.
Regards

Originally Posted by Phil Spencer

Don't muck around take it to a qualified motor repairer, all the above information is wrong your motor will still run in reverse you have inadvertently reversed a connection somewhere besides if your insulation is cracking it would be worth having a qualifier repairer fit new tails to the windings and have the thing re-varnished and baked. But on the other hand if you want to electricute your self go ahead and keep doing what you are doing

No need to shout.
I wasn't mucking around with the motor ,I was seriously trying to fix it.I was at least partly successful as it no longer trips the main breaker .
All the wires are in the correct place , how do I know , because they are all numbered and I have the electrical diagram for the connections.
It's more than cracked insulation .The wires with the cracked insulation have been replaced ,the motor runs but has no torque and will run in either direction when switched on and off .
So none of the information above is wrong .

You need to carefully re read what was written in my post . .

The only place in town is an electrical contractor , I doubt he has the resources to actually repair it , would be able to test it and tell me what I already know .
The motor will need to be sent away and it's probably not worth the effort and expense .

Kev.

The capacitor value is correct. It has a start wind which acts as a drop to voltage. Only if you hammered that motor and saturated the winding would the voltage exceed the capacitor rating.
Personally I would suspect the motor winding is damaged and the only way to tell is to read the winding. It could be open circuit, (over 100 ohms) With a 1 flashing on your meter this sounds likely. Or it may have flashed over. Now doing this will kill the transformer properties (Impedance) and unless you have some fancy gear you cant check that.
The motor sounds like a cheap Chinese version where they can use it as 3 phase 110V or slop in a big capacitor and use it as single phase. Your capacitor is not the usual value as a start cap but is used as a phase shift plus start, I think you will find cost wise this is beyond repair.

Hi Kev,
Sorry to hear you have problems, I haven't replied in this thread because I can't help out in the electric motor department, but I am sure some of our electrical minded/ talented members will help you sort it out.

Why is it that people get on hear saying (or shouting) take it to a qualified motor guy, if you where going to do that it would be already their and you wouldn't be asking the question.
You have already said in your first post that you took the motor apart and replaced some of the wires etc and your still here posting not electrocuted, do they think everybody is completely stupid?
I remember a thread when a guy asked about using a 15 amp welder plug in a 10 amp power point.


I hope you get it sorted soon.

Dave

[QUOTE=Dave J;1266753]
I remember a thread when a guy asked about using a 15 amp welder plug in a 10 amp power point.
/QUOTE]

every one does that....thats why nails were invented....

I am with mike...the capacitor details seem reversed.......juts my 2bobs worth

Yeah , I worked in the power generation industry for many years as a power station tech , on diesels and gas fired turbines pumping out big voltages 22KV and 66KV , I am well versed about electrical safety even though I'm not an electrician .I do have a high voltage operators qualification and have the utmost respect for electricity having seen some spectacular electrical events in the time I was in the industry .
If you have seen the damage from a exploding transformer or the arcing that can happen when breaking high voltage switching gear you will know what I mean.
Any power points and electrical appliances in my home are always repaired /replaced by an electrician.
I have dismantled many electric motors in the past and repaired a few ,working in conjunction with electricians on occasions , and gaining some knowledge .
I guess because I had the experience this is why I did this with the mill motor .
I have learnt a lot in the past few days so its not a total loss ,it will go into the mental library .
I'm going to remove the motor today and will drop it off to get tested tomorrow ,If it is dead or beyond economical repair I will bury it ,and source a motor from Royce Cross Agencies in Adelaide.
Hoping that I can get some thing with the physical dimensions similar or very close to what is needed.
Probably will be looking for ideas regarding a quick adjustable mount for it later as the mounting that is currently in place is less than ordinary.
Thanks all for your input and advice on my problem ,even the electrical safety aspect.

Kev.

Hi,
It is not that we think every one is stupid, you just do not know, so if it is taken to the right person they can physically see it and not go on a vague and incomplete description. The thing that scares me is that some of the answers show absolutely no knowledge of the subject and those that know what they are talking about assume a knowledge the reader (who may or may not be the person who originally asked) may or may not posses.
So my advice is always call in some one qualified.
I am just explaining my position and not having a go at any one in this post so I hope I have not offended.
Yours in the hobby,