Quantcast
  • We invite you to join UKWorkshop.
    Members can turn off viewing Ads!

Got 99 problems and the motor is one

UKworkshop.co.uk

Help Support UKworkshop.co.uk:

Trevanion

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
Got a minor electrical/motor problem, so I thought I’d ask the hive mind of higher knowledge :D

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

Established Member
Joined
25 Jan 2018
Messages
170
Reaction score
17
Location
Cambridge
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

Established Member
Joined
31 Dec 2004
Messages
20,131
Reaction score
71
Location
Cotswolds UK
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

Shy Tot
Joined
6 Aug 2008
Messages
3,429
Reaction score
679
Location
@dougsworkshop
Does the pulley spin freely when the belts are off? Just wondering if the bearings are in good condition :-k
 

Trevanion

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
peter-harrison":h7ygautk said:
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.

CHJ":h7ygautk said:
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.

Doug B":h7ygautk said:
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

Established Member
Joined
31 Dec 2004
Messages
20,131
Reaction score
71
Location
Cotswolds UK
Trevanion":15bb2zop said:
[..
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

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
CHJ":rasuky26 said:
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

AKA 9Fingers
Joined
19 Jan 2013
Messages
2,300
Reaction score
113
Location
Southampton area
Trevanion":1eo0pz0u said:
CHJ":1eo0pz0u said:
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

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
Myfordman":24tf7dj1 said:
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

AKA 9Fingers
Joined
19 Jan 2013
Messages
2,300
Reaction score
113
Location
Southampton area
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

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
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.

Myfordman":26884k1g said:
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:
 

Trevanion

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
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

AKA 9Fingers
Joined
19 Jan 2013
Messages
2,300
Reaction score
113
Location
Southampton area
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

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
Myfordman":1nhokheh said:
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

AKA 9Fingers
Joined
19 Jan 2013
Messages
2,300
Reaction score
113
Location
Southampton area
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

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
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 :D

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!
 

Trevanion

Greatest Of All Time
Joined
29 Jul 2018
Messages
3,775
Reaction score
567
Location
Pembrokeshire
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. :D

Many thanks again Bob!
 

Myfordman

AKA 9Fingers
Joined
19 Jan 2013
Messages
2,300
Reaction score
113
Location
Southampton area
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
 
Top