Got 99 problems and the motor is one

[Trevanion]

Got a minor electrical/motor problem, so I thought I’d ask the hive mind of higher knowledge

I’ve been fixing up this old machine which at some point had had a motor swap from a three phase motor to a single phase Axminster one with two capacitors on top. I’ve put a new starter switch on the machine and a more heavy duty flex on it (steel braided 5 core wire, joined wire 1&2 for live and 3&4 for neutral). The motor has 3 belts on it, 2 run the cutterblock and the third the power-feed, I tightened them up not super tight but what I felt was good enough/still able to turn the belt 90 degrees.

It started up beautifully about 4 times with no sign of strain on start up. And then it started not wanting to start properly with that classic “brrrt” noise, even with the belts slackened up it didn't want to start, giving the machine a bit of motivation by turning the flywheel helps but still there’s a lot of strain trying to get it up to speed. With the belts off and it does start but there seems to be a tiny bit of resistance in the first second or so. I don’t think supply is an issue as I’ve got it on a 32amp plug with adequate supply going in, and the overload on the starter is set right or the motor. Motor does seem to get a bit warm after trying to start it but I would think it would anyway if the fan wasn’t turning.

I’m thinking it could be the capacitors but I’m not 100% on that as usually the motor wouldn’t want to start at all with a dodgy capacitor, but I don’t have massive amounts of experience with this kind of thing anyway. One capacitor is 35 microfarad and the other is 200 microfarad from what I could tell off them. I could get new capacitors but I don’t want to spent the cash if it’s clearly something else.

Anyone got any ideas?

 

[peter-harrison]

If it hums but doesn't turn when you switch it on, but runs when you give it a flick, it's the capacitor. I don't know enough to say which one is broken, but you can often tell by looking. It may well have some leakage etc. I generally take mine to my local electric motor rewinds people and they can put a meter on it to check. It's usually about £10 for a replacement. To make them last longer, try to cut down stops and starts (they get hot)

 

[CHJ]

Two Capacitors?

Is it a centrifugally switched motor (did you hear distinctive click/clunk noises when stopping/starting)

Check that the switch is moving freely against its springs, usually accessible or can be seen inside the rear motor casing behind the cooling fan assembly

 

[Doug B]

Does the pulley spin freely when the belts are off? Just wondering if the bearings are in good condition :-k

 

[Trevanion]

If it hums but doesn't turn when you switch it on, but runs when you give it a flick, it's the capacitor. I don't know enough to say which one is broken, but you can often tell by looking. It may well have some leakage etc.

Runs with a flick with the belts on, albeit with a 10-second ramp-up to full speed. Seems to start alright with belts off. As far as I could see both capacitors look OK, no swelling or leakage to speak of but they can go without any sign of damage from experience.

Two Capacitors?

Is it a centrifugally switched motor (did you hear distinctive click/clunk noises when stopping/starting)

Check that the switch is moving freely against its springs, usually accessible or can be seen inside the rear motor casing behind the cooling fan assembly

Yes, I also found it a bit strange that there were two capacitors. The box on the motor is moulded for two capacitors so it isn't some bodge down the line. It is a centrifugal switch motor and it seems to be all in good working order as I had the motor apart to check it and the bearings a couple of months ago when I started the project.

Does the pulley spin freely when the belts are off? Just wondering if the bearings are in good condition :-k

It doesn't spin absolutely freely like how a motor with dry bearings would spin for 20 rotations or so, it spins with a little resistance and stops after about 3 or so turns as you would get with fresh bearings although they aren't new.

Photos of the top of the motor and the capacitors if it helps:

 

[CHJ]

[..
It doesn't spin absolutely freely like how a motor with dry bearings would spin for 20 rotations or so, it spins with a little resistance and stops after about 3 or so turns as you would get with fresh bearings although they aren't new.

That is most likely just the centrifugal switch mechanism rubbing , not a problem, check you have continuity of connection across the wiring to and across the centrifugal switch in this stationary closed condition.

 

[Trevanion]

check you have continuity of connection across the wiring to and across the centrifugal switch in this stationary closed condition.

:shock: This is quickly becoming rocket science of which I have no idea about. When the motor was running I believe the centrifugal switch was working fine as it was clicking off when it was running down.

 

[Myfordman]

check you have continuity of connection across the wiring to and across the centrifugal switch in this stationary closed condition.

:shock: This is quickly becoming rocket science of which I have no idea about. When the motor was running I believe the centrifugal switch was working fine as it was clicking off when it was running down.

So are you saying it is getting too complex for you and are giving up or are you still after guidance?

 

[Trevanion]

So are you saying it is getting too complex for you and are giving up or are you still after guidance?

I have waaaay too much time and money invested in this machine to give up now :lol:

I'm still after guidance but I'm a real dunce on electrics once you go beyond a screwdriver and a pair of pliers.

 

[Myfordman]

Then you are going to have to be a fast learner lol

Three things need to be right to get is to start properly.
1 the start capacitor needs to working - the high value one
2 the centrifugal switch needs to be opening and closing correctly
3 the start winding needs to be good.

By starting it unloaded you have possibly proved the start winding is good. To be sure, with the power off, spin the motor the wrong way from normal (wind stout string several times round the pulley and yank hard, LET GO then power up.
If it continues to run in the wrong direction then the start winding is suspect. If it corrects the direction of rotation and spins up then the start winding is probably OK. In this test the starting power is weak as the motor is starting on the run capacitor which is permanenty connected to the start winding
When you switch off, as it slows down you should hear a bit of a click followed by a rubbing sound.
Next you need to open up the motor to get to the centrifugal switch. Sometime of chinese motors this is behind the fan under its own cover. Be very very careful taking the fan off not to break a blade off. These fans are made of unobtainium and with a blade boroken off with vibrate badly. most have an odd number of blades so you can just break another one off to re-balance it.
When you get to the switch make sure the contacts are clean (fine emery to clean) and not welded shut. You can operate the flying weights manually to see the switch move.
Put it all back together and re-test. If you still have gut-less starting then get a new start capacitor. loads on ebay for not much money. go for similar capacitance (mfd) and same or greater voltage. There is not much you can do to test a capacitor with out more knowledge than you possibly have equipped with pliers and screwdriver lol

 

[Trevanion]

Cheers Bob, When I get a bit of time which will probably be tomorrow night I'll give your suggestions a shot and will report back. I think I'll have to disassemble the motor to get at the centrifugal switch, it was only a few months ago I was looking at the switch but I cannot for the life of me remember whether I needed to take it completely apart or not.

There is not much you can do to test a capacitor with out more knowledge than you possibly have equipped with pliers and screwdriver lol

You'd be amazed at what I can achieve with a pair of pliers and a screwdriver :wink:

 

[Myfordman]

I could test the capacitor for you but to be honest postage both ways would be about the price of a new one anyway.
like this https://www.ebay.co.uk/itm/200UF-200MFD ... SwyqhdKFZE

 

[Trevanion]

Sorry It's taken me so long to get back to you Bob, life... :roll:

I tried the string around the pulley in the wrong direction trick, it started up back in the correct direction. So that seems fine.

I haven't checked the centrifugal switch, but last time I checked it was all fine, clean and it still seems to switch off and on fine when there's no load on the motor. I don't think that's the problem but I could be totally wrong there.

I've taken out the 35UF 450V capacitor to try a couple of capacitors off a couple other machines, namely a 20UF 450V and a 60UF 450V, these didn't work even when the motor wasn't under load. I then tried a 30UF 220V capacitor and it started up a treat even with all the belts on, not sure what that means, I'm not going to use the 30UF capacitor of course as it isn't correct and it would burn up after a little while (It got quite hot from just starting it a couple of times)

I've got a multimeter that can read capacitance but this kind of thing is a little beyond me, I tried it on the 35UF capacitor and it seemed to read 34.95 which I would assume is correct. Not sure if that's the right way of going about testing one.

The only thing I haven't done anything with is the 200UF 265V capacitor, but I would assume this one is fine as it's the run capacitor? Again, no idea.

 

[Myfordman]

The reversing and correct running direction test proves that the start winding is OK and that the RUN capacitor of 35uF is working ok.
I'm not sure why some of your tests with different value run capacitors enabled starting with the belts on.

The START capacitor is the high value one and is switched in and out by the centrifugal switch we need to prove both the capacitor and the switch. As you have a capacitance meter, measure the 200uF one with one end disconnected. This only does a low voltage, low current test but it is worth checking.

Next you need to find a 240 filamant lamp as powerful as possible. One of those 500 watt halogen worklights would be ideal but a 100watt old fashioned bulb would do fitted in a table lamp or similar. take the plug off and connect the blue/brown wires across the centrifual switch in parallel. make sure the lamp is switched on.
Try starting the motor. Initially the lamp should be off and then it should come on (not necessarily at full brightness) once the motor is running. This should test the centrifugal switch. When you turn off the power the light will go out almost immediately and after a second or so you should hear the centrifugal click then rub as the motor slows down. If the light was on as soon as you applied power, then the switch is stuck open if it never comes on then the switch is stuck shut. If the motor is failing to start under load, then it is pointing towards the starting capacitor being defective. The link I provided earlier should get you a replacement at reasonable cost.

Good Luck

 

[Trevanion]

The reversing and correct running direction test proves that the start winding is OK and that the RUN capacitor of 35uF is working ok.
I'm not sure why some of your tests with different value run capacitors enabled starting with the belts on.

The START capacitor is the high value one and is switched in and out by the centrifugal switch we need to prove both the capacitor and the switch. As you have a capacitance meter, measure the 200uF one with one end disconnected. This only does a low voltage, low current test but it is worth checking.

Next you need to find a 240 filamant lamp as powerful as possible. One of those 500 watt halogen worklights would be ideal but a 100watt old fashioned bulb would do fitted in a table lamp or similar. take the plug off and connect the blue/brown wires across the centrifual switch in parallel. make sure the lamp is switched on.
Try starting the motor. Initially the lamp should be off and then it should come on (not necessarily at full brightness) once the motor is running. This should test the centrifugal switch. When you turn off the power the light will go out almost immediately and after a second or so you should hear the centrifugal click then rub as the motor slows down. If the light was on as soon as you applied power, then the switch is stuck open if it never comes on then the switch is stuck shut. If the motor is failing to start under load, then it is pointing towards the starting capacitor being defective. The link I provided earlier should get you a replacement at reasonable cost.

Good Luck

Ah, I had assumed the higher voltage rated capacitor was the start one. It makes sense that it's the higher UF rating #-o I'll try to measure the 200UF capacitor tomorrow and see if anything obvious shows.

Think I've also got a powerful brooding lamp somewhere from the dog manufacturing days, If I can dig it up I'll give it a shot testing the switch. But since I can hear it click on and off and rubbing when the motor runs up and coming down from speed surely that means it's neither stuck open or shut?

 

[Myfordman]

No the click is showing that the weights are moving only. The contacts can be damaged and not making contact or still be welded together and the mechanical bit will still sound like it is working.

 

[Trevanion]

Right...

I have taken the motor out of the machine to give it a proper look over without constrictions. Took the rear end of the motor off to get at the centrifugal switch, wasn't there... It's on the spindle end of the motor #-o So took that end apart and had a good look at the switch. As far as I could see the switch is engaged when static and when the weights move it is disengaged properly which looks to me to be correct. I gave the contacts a rub with some 320G whilst I was there because they looked a little grubby and then put the motor back together.

Next stop 200UF capacitor, did as you said and checked it with 1 terminal still attached and got nothing on the meter, checked it with both terminals removed and still nothing except 00.08, went back and checked another capacitor to check the meter was working properly and it read fine.

I think I've found the culprit

Thanks a lot Bob! As I said, once it goes beyond pliers and a screwdriver it gets a bit beyond me but I have now learned quite a bit from this little exchange. I think I'll be a little more confident with troubleshooting motors in the future I'll get a new capacitor on order and give it a go again and hopefully, that will be that!

 

[Myfordman]

Sounds like you are on the home straight now!
You will soon be making shavings again.

 

[Trevanion]

So sorry that I never got back to this, totally forgot all about the thread #-o

Replaced the 200UF capacitor and it started up a treat with no issue.

Many thanks again Bob!

 

[Myfordman]

Excellent news. Not only do you have a running motor but also increased "have a go" confidence of use of both hammer and multimeter!

Bob