Chester Super Lux – Motor Failure

[Colin HeseltineParticipant @colinheseltine48622]

Using my Chester Super Lux mill today for a couple of house. Working quite happily no issues at all. Stopped whilst checked a couple of dimensions, hit start and all I got was a humming noise. Nothing tripped out, no smells smoke or anything like that.

Although had machine for around possible ten years I guess it has not done more than 20 or 30 hours work in that time.

Any one any idea as to what might have failed.

Colin

[Colin HeseltineParticipant @colinheseltine48622]

[shaun hillParticipant @shaunhill88399]

I had a similar problem on mine, turned out the start capacitor had packed up, put a new one on, went for years more

[Neil WyattModerator @neilwyatt]

My bandsaw had the same symptoms,m except I coudl start it by pulling on a belt. Once again a new start capacitor fixed it.

Use the same of close capacitance value and make sure you have the same voltage rating as the old one.

Neil

[Colin HeseltineParticipant @colinheseltine48622]

I tried the mill this morning and on second attempt it started.

The capacitor is a CD60 250volt, 150 microfarad.. Other than Hong Kong does anyone have any suggestions as to where to find similar sized capacitor.

Thanks,

Colin

[Les Jones 1Participant @lesjones1]

This is one possible source

asAAOSwlHBZ0hn1:rk:3f:0″>https://www.ebay.co.uk/itm/Motor-Start-Starting-Capacitor-150uf-150mfd-microfarads-230V-250V-300V/122735905448?hash=item1c93a14aa8:gasAAOSwlHBZ0hn1:rk:3f:0

 Before buying a new capacitor check that the centrifugal switch is closed when the motor is stopped. If you don't know how to do this you will need to post a picture of the connection box on your motor.

Les,

Edited By Les Jones 1 on 25/11/2018 12:17:58

Edited By Les Jones 1 on 25/11/2018 12:18:53

Edited By Les Jones 1 on 25/11/2018 12:20:14

Edited By Les Jones 1 on 25/11/2018 12:20:50

[Neil WyattModerator @neilwyatt]

I'd be tempted to upgrade to a 450V capacitor for long life.

Neil

[Martin ConnellyParticipant @martinconnelly55370]

As Neil says don't get a 250V capacitor. Mains voltage of 230V rms has a peak voltage of 325V. Unless you know for certain that the 250V is an rms value you run the risk of rapid failure again.

Martin C

[Les Jones 1Participant @lesjones1]

I agree that it worth getting a 450 volt rated capacitor if you can.

Les.

[Colin HeseltineParticipant @colinheseltine48622]

I know that my mains voltage tends to be high. I have a UPS that regularly held the voltage down as it was experiencing voltages greater than 250v.

I have put pictures of the existing capacitor and motor junction box in my album, For some reason they will not add to this post.

Les, I do not know how to check centrifugal switch. Picture of junction box is in my album

Colin

[JonParticipant @jon]

Two caps on mine.

For what its worth mine has been used daily since 2004 to 2010 approx 2hrs a day, 2010 onwards approx 5 hrs a day. Only in peak times the supply voltage drops to around 253v, often 260v+

Wish it been the motor that packed up on mine, but just about everything else. Motor would have changed for a faster jobby, fastest speed is just too slow at 1250 rpm making that 1hr job take 2hrs or more.

[Les Jones 1Participant @lesjones1]

Hi Colin,
I can't follow The wires in the connection box well enough to identify the connections to the centrifugal switch directly. I think I can follow it well enough to see that the capacitor connects to the top two terminals. If you disconnect one of the wires to the capacitor then measure the resistance between these two terminals I would expect you to get a reading of about 10 ohms.(I am guessing it will be about a 0.75 HP motor. It would be lower on a larger motor.) This reading will be the centrifugal switch in series with the main and start windings. If the switch is open circuit the reading will be quite a lot higher. (A high reading could also be caused by one of the windings being open circuit but this would be unlikely,) You could do a very rough test of the capacitor by connecting a 100 watt old fashioned tungston filiment lamp in series with the capacitor, When connected to thje mains via the capacitor the lamp should light almost as bright as if connected directly to the mains. As the reactance of a 150 uF capacitor at 50 hz is about 21 ohms the voltge across the capacitor should be about 8 volts. Only try this if you are confident working with live mains circuits.

Les.

[Colin HeseltineParticipant @colinheseltine48622]

Only just had chance to take a look. Powered on and worked 4 or 5 times. Enough to think will set a job up to mill couple of slots in an arbor. Got job almost centered and it stopped again.

Took left hand capacitor lead off junction box and put meter across capacitor connections on junction box (no reading), tried across capacitor leads no reading. Meter set to 20 ohms scale, displays a 1 when nothing connected sand still displays a 1 when connected across the junction box or the capacitor.

Loathe to try live electrical test as no one else at home at present.

Pictures of junction box, electrical circuit and motor plate below.

Colin

[Dave HalfordParticipant @davehalford22513]

It's hard to test a cap with a digital meter, the discharge kick is often too fast to operate the display.

[Les Jones 1Participant @lesjones1]

If the machine is still in the not working condition do the following WITH THE POWER REMOVED. Disconnect the wires U1 and U2 from the motor terminals. (These are probably the run winding.) Measure the resistance between the teminals they were removed from. If you get a low reading Less than about 15 ohms then this is the run winding. (If you get a low reading go to step 2. If you get a very high or infinite resistance reading then this will be the start winding in series with the capacitor and centrifugal switch. With the meter leads still on the terminals short out the capacitor terminals. If the centrifucal switch is close (Which it should be with the motor stopped.) then the meter should give a low reading. ( Less than about 20 ohms.) If you still have a high reading then the centrifugal switch is faulty. Goto End.
Step 2 Connect the meter leads to V1 and the bottom left hand terminal. (The lable is obscured by wires. I think it will be Z2 or W2) You should get a high reading. Short the capacitor connections. The reading should drop to less than 20 ohms. If it remains high the the centrifugal switch is faulty.

End. Report the results.
One other question. When it failed disd it fail in both forward and reverse ?

Les.

[Brian WoodParticipant @brianwood45127]

Colin,

Your starting fault is now beginning to sound like dirty points in the centrifugal switch; sometimes it makes and sometimes it doesn't.

I would still change the capacitor to an up-rated version while you have the chance.

Regards

Brian

[Les Jones 1Participant @lesjones1]

Just reading though the post again we could be jumping the the conclusion that the motor is faulty. Nothing has been done to verify that the conractor KM1 is being energised. That needs to be checked next time the fault occures.

Les.

[JonParticipant @jon]

Same motor as mine Colin.

Seen similar endless times, what happens when you give the spindle a push start?

[Colin HeseltineParticipant @colinheseltine48622]

Les,

Carried out step 1. and get reading of 3.1 or 3.2 ohms across terminals (2 different test meters)

Step 2 – NO reading on either of two meters. As I did not get a reading I did not short out the capacitor connections.

Checked the contactors – they are pulling in

Behave the same whether in forward or reverse.

Also tried rotating the motor (via fan blades) whilst attempting to start – this did not have any effect.

Colin

 

 

 

Edited By Colin Heseltine on 10/12/2018 14:38:18

[Colin HeseltineParticipant @colinheseltine48622]

Further to last comments. I have just checked voltage coming into my home. My computer UPS is reporting todays voltages Min=242v, Max 248v. Over last months seen just over 250v several times.

I am located about 20meters from substation, from which I have a 100amp 3 phase feed.

One of my testers it appears can check capacitors.  The readings appear to vary.  Get values from 0.18nf through to 8.16nf  The display then appears to microF then shows a value of 0.

I have no idea how a nf compares to a microF 

Colin

Edited By Colin Heseltine on 10/12/2018 15:24:55

[Les Jones 1Participant @lesjones1]

When you say that you did not get a reading do you mean that you got an infinite reading ? An infinite (Or at least very high.) reading is what I would expect with the start winding in series wth the capacitor and centrifugal switch. The idea of shorting the capacitor out is so you measure the resistance of the start winding in series with the centrifugal switch, that should be quite low less than 20 ohms. I have no susspicion that there is any problem with your mains supply.

Les.

[Colin HeseltineParticipant @colinheseltine48622]

Les.

By no reading I mean he display on meter does not change from that shown when nothing connected. As per picture below.

I commented about the voltages that I see at home as several people had commented earlier that it would be a sensible thing to upgrade the capacitor from 250v rating to a 450v rated device. Though I am struggling to find one other than in China with a suitable long lead time.

I shorted out the capacitor terminals whilst carrying out step 2 but the meter reading stayed as per photo.

Colin

[Les Jones 1Participant @lesjones1]

Hi Colin,
The OL display means that the resistance that you are trying to measure is higer than the meter can read on the range it is set to. If the reading did not drop to a low value when the capacitor was shorted out then the centrifugal switch or the start winding is open circuit, (It is not likely to be the start winding.) If the capacitor really does only have a capacitane of a few nF then it is faulty. (There are 1000 nF in 1 microfarad.) I find it difficult to believe that both the capacitor and centrifugal switch are faulty.

Les.

[Colin HeseltineParticipant @colinheseltine48622]

I will try Chester machine tools in the morning, their Burntwood site is only a few miles from my location. Will see if they have a capacitor in stock. Have you ever opened up this particular motor.

I assume that once I have levered the fan off (no fixing screws just a location flat on the shaft) and undone the three screws around the perimeter of the end case it should just lift off. Hopefully the connections to the end case will be on spade terminals.

Colin

[SillyOldDufferModerator @sillyoldduffer]

Posted by Colin Heseltine on 10/12/2018 15:00:44:

…

One of my testers it appears can check capacitors. The readings appear to vary. Get values from 0.18nf through to 8.16nf The display then appears to microF then shows a value of 0.

I have no idea how a nf compares to a microF

…

Probably doesn't help with your main problem but there are:

• 1000 picofarads in a nanofarad
• 1000 nanofarads in a microfarad.

Your meter is trying to display the measurement in the scale providing best accuracy. 900nF is more meaningful than 1uF. Unfortunately capacitors are tricky beasts to measure with a multimeter. Being a low voltage device a multimeter can't test for high voltage breakdown, which is a common capacitor fault. Also the test leads have to make a good sustained contact with the terminals. Any wobble or dirt and you will get duff readings. And, because of the simple way the test is done by the meter a faulty capacitor can thoroughly confuse it. The scale jumping about and/or getting different answers is typical of bad tests as well as a sick capacitor.

The other major problem is that it's very difficult to measure a capacitor if it's wired into a circuit. At least one terminal has to be disconnected to get a meaningful reading, ideally both. If you don't take a clean reading then the meter is likely to be completely discombobulated by whatever else is wired to the capacitor. As there's so much opportunity for being misled. I believe motor repairers are more likely to instantly replace an even slightly suspicious capacitor than to mess around trying to measure it.

Given all these shortcomings you might wonder if capacitance ranges on a multimeter are worth having at all! Mine is mostly used to check brand-new components, not because I suspect they're faulty, more as a quick way of confirming they're the right value – the printing is tiny.

Dave

Edited By SillyOldDuffer on 10/12/2018 17:46:41

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