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Dead CamVac motor

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Dead CamVac motor

Postby RogerS » 31 Jul 2019, 18:37

One of the motors in my Camvac started smelling very 'hot electric' and threw the RCD.

Am I right in thinking that this is terminal ? :(

Measuring resistance between live or neutral and earth is showing open-circuit (but it could be breaking down under 240v of course). Resistance between L and N is the same as the other motor.
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Re: Dead CamVac motor

Postby 9fingers » 31 Jul 2019, 19:41

RogerS wrote:One of the motors in my Camvac started smelling very 'hot electric' and threw the RCD.

Am I right in thinking that this is terminal ? :(

Measuring resistance between live or neutral and earth is showing open-circuit (but it could be breaking down under 240v of course). Resistance between L and N is the same as the other motor.


Am I right in thinking the camvac uses "spawn of the devil" brush motors. If so it is possibly that brush carbon thrown out by the motor is causing an earth leakage.

Patient dismantling and cleaning might get it running again.

Bob
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Re: Dead CamVac motor

Postby RogerS » 31 Jul 2019, 21:19

9fingers wrote:
RogerS wrote:One of the motors in my Camvac started smelling very 'hot electric' and threw the RCD.

Am I right in thinking that this is terminal ? :(

Measuring resistance between live or neutral and earth is showing open-circuit (but it could be breaking down under 240v of course). Resistance between L and N is the same as the other motor.


Am I right in thinking the camvac uses "spawn of the devil" brush motors. If so it is possibly that brush carbon thrown out by the motor is causing an earth leakage.

Patient dismantling and cleaning might get it running again.

Bob


Dead right...brush motor. Will probably stick further investigation as you suggest at location 1,344,555 on the TUIT list :cry: I still have one working.
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Re: Dead CamVac motor

Postby 9fingers » 31 Jul 2019, 21:32

RogerS wrote:
9fingers wrote:
RogerS wrote:One of the motors in my Camvac started smelling very 'hot electric' and threw the RCD.

Am I right in thinking that this is terminal ? :(

Measuring resistance between live or neutral and earth is showing open-circuit (but it could be breaking down under 240v of course). Resistance between L and N is the same as the other motor.


Am I right in thinking the camvac uses "spawn of the devil" brush motors. If so it is possibly that brush carbon thrown out by the motor is causing an earth leakage.

Patient dismantling and cleaning might get it running again.

Bob


Dead right...brush motor. Will probably stick further investigation as you suggest at location 1,344,555 on the TUIT list :cry: I still have one working.


Ah then when the second one fails you will be up "dust creek without a collector" :lol:
Something to do when you wake up at silly o'clock in the morning maybe?
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Re: Dead CamVac motor

Postby RogerS » 31 Jul 2019, 21:34

9fingers wrote:
RogerS wrote:
9fingers wrote:..

Am I right in thinking the camvac uses "spawn of the devil" brush motors. If so it is possibly that brush carbon thrown out by the motor is causing an earth leakage.

Patient dismantling and cleaning might get it running again.

Bob


Dead right...brush motor. Will probably stick further investigation as you suggest at location 1,344,555 on the TUIT list :cry: I still have one working.


Ah then when the second one fails you will be up "dust creek without a collector" :lol:
Something to do when you wake up at silly o'clock in the morning maybe?
Bob



Nope...still OK as I can jury rig the Axminster chip collector ! :D
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Re: Dead CamVac motor

Postby 9fingers » 31 Jul 2019, 21:39

Just pausing for thought......

Motor smelling hot etc does not quite match tripping the RCD.

30ma trip at 240 v is 7.2 watts. not enough to raise enough heat to smell much? Maybe you meant it tripped the MCB perhaps?

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Re: Dead CamVac motor

Postby RogerS » 01 Aug 2019, 04:56

9fingers wrote:Just pausing for thought......

Motor smelling hot etc does not quite match tripping the RCD.

30ma trip at 240 v is 7.2 watts. not enough to raise enough heat to smell much? Maybe you meant it tripped the MCB perhaps?

Bob


LOL...I thought that when I was posting I should confirm that it was the RCD and not the MCB but forgot! Defo the RCD.
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Re: Dead CamVac motor

Postby RogerS » 06 Aug 2019, 16:48

OK...a spare moment while paint was drying and I've taken it apart. Commutator is OK, I think.

Image

but not sure about the brushes. I think they've had it.

Image
and in the one above it looks like part of the brush support is actually touching the commutator.

Image

I put on a pair of goggles, got the torch ready in case the RCD went and fired up the motor. Lots of arcing from that area where I think it's the brush support. And the smell.

Still not sure why the RCD trips though.

If it is the brushes, are they easily obtainable ?
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Re: Dead CamVac motor

Postby Andyp » 06 Aug 2019, 16:58

I do not think therefore I do not am.

cheers
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Re: Dead CamVac motor

Postby 9fingers » 06 Aug 2019, 16:59

You need to find out how/why the brush guide is not inline with the commutator.

It looks like the brush boxes might be fixed on with screws and thus removeable.

I expect camvac might have new brushes at a price. Ideally find out what the motors are normally fitted to and maybe the OEM spares will be better prices. if all else fails, my recent posting about brushes gives a possible source - they even make brushes to fit particular dimensions.

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Re: Dead CamVac motor

Postby RogerS » 06 Aug 2019, 17:10

Update. I don't think it is the brushes as I disconnected the motor so I could get easier access and undid the screws holding down the brush assemblies and there is a good 15mm + of brush in each of them. They also freely push in and out against the spring.

So unless anyone has any better idea, tomorrow I'll leave it turned on until the RCD trips and try and see what's happening. Fingers well clear.
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Re: Dead CamVac motor

Postby 9fingers » 06 Aug 2019, 17:16

RogerS wrote:Update. I don't think it is the brushes as I disconnected the motor so I could get easier access and undid the screws holding down the brush assemblies and there is a good 15mm + of brush in each of them. They also freely push in and out against the spring.

So unless anyone has any better idea, tomorrow I'll leave it turned on until the RCD trips and try and see what's happening. Fingers well clear.



But why is the brush guide on the pi88 with respect to the commutator?

Good job you dont need brushes at that price!!

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Re: Dead CamVac motor

Postby RogerS » 06 Aug 2019, 17:23

9fingers wrote:
RogerS wrote:Update. I don't think it is the brushes as I disconnected the motor so I could get easier access and undid the screws holding down the brush assemblies and there is a good 15mm + of brush in each of them. They also freely push in and out against the spring.

So unless anyone has any better idea, tomorrow I'll leave it turned on until the RCD trips and try and see what's happening. Fingers well clear.



But why is the brush guide on the pi88 with respect to the commutator?

....

Bob


Sorry Bob, I don't understand
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Re: Dead CamVac motor

Postby 9fingers » 06 Aug 2019, 17:38

RogerS wrote:
9fingers wrote:
RogerS wrote:Update. I don't think it is the brushes as I disconnected the motor so I could get easier access and undid the screws holding down the brush assemblies and there is a good 15mm + of brush in each of them. They also freely push in and out against the spring.

So unless anyone has any better idea, tomorrow I'll leave it turned on until the RCD trips and try and see what's happening. Fingers well clear.



But why is the brush guide on the pi88 with respect to the commutator?

....

Bob


Sorry Bob, I don't understand


You were the one to point it out as a problem??

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Re: Dead CamVac motor

Postby RogerS » 06 Aug 2019, 18:30

My bad! It's OK.
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Re: Dead CamVac motor

Postby RogerS » 07 Aug 2019, 09:30

Back to first principles.

The RCD trips.

This means that there is leakage to earth from the motor when it's powered up.

Problem - how to determine that this is the case.

It's pointless me sticking the motor on the bench and applying power because if I stick one of those neon screwdrivers on the metal casing, the chances are that it will still light up because (a) it's a high-impedance monitoring device and (b) there will be an induced voltage in the metal casing (as it's not earthed at the moment on the bench).

Even if I try and measure any voltage between the metal casing and earth with a multi-meter, chances are that I will see a reading because the multimeter is also (a) and (b) from above.

So seems to me that the only route I can take is to get hold of an insulation resistance tester.

Bob..is this logic sound ? Is there any alternative approach I can use ?

One further thought...I did smell hot electric and so maybe if I simply power it up on the bench and wait and see what happens :eusa-think: Could be a good test for the smoke alarm :lol:
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Re: Dead CamVac motor

Postby Robert » 07 Aug 2019, 09:54

240v divided by .03A trip current for the RCD means a resistance of 8k ohm which should be readable on a multimeter set to resistance... if it is a simple resistive leak to earth.

The fact that it runs, smells hot then trips sounds like a wire is heating and expanding until it touches something and shorts to earth. Maybe time it to failure as is then leave it a few hours to cool and try again with compressed air blowing on the motor. If it lasts longer then something heating up is the problem.
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Re: Dead CamVac motor

Postby 9fingers » 07 Aug 2019, 09:56

Some fundamentals.

The rcd trips because the total current in live and neutral differs by around 30mA.
Usually this suggests a leakage to earth but not always.

All the devices on that RCD circuit can contribute leakage. 29 devices each leaking 1mA plus another leaking at 2mA results in a trip.

1-2mA leakage is not a problem but too many and the RCD will trip. This is why RCDs are the second spawn of the devil! :lol:

As regards your testing. Connecting just L & N to the motor can never cause a trip as there can be no differential current. You need to give it a path to earth to see if there is really some leakage.
If it trips then remove as many other loads from that RCD circuit and then see if it still trips.
If so then you probably do have a leakage path in that motor.
Add a mains filament light bulb in series with the motor body to earth.
Measure the ac volts developed across the bulb. If this is only a few volts, then connect the meter on AC current range in series with the bulb to earth and now you are measuring the leakage current (reduced a bit by the bulb but this is there as a safety measure don't test without it!)

Don't do these tests with any part of the camvac wiring. You want to make sure you are testing the motor alone. Remember that the camvac has a mains filter fitted and these are notorious for causing leakage paths even when they are working properly.

DO clamp the motor to the bench or in a vice when running it. they start with a kick and un clamped they will fly across the room. DAMHIKT.

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Re: Dead CamVac motor

Postby RogerS » 07 Aug 2019, 10:06

Thanks chaps.

Before I go grovelling and trying to find a bulb socket :lol: perhaps you'd like to take a look at this video.

Something looks hot, I think.

[youtube]O4j1ryWCEMQ[/youtube]
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Re: Dead CamVac motor

Postby Woodster » 07 Aug 2019, 10:14

Oh dear, that doesn’t look good! Shame as Camvac make what are normally the quietest shop vacs on the market. It would be nice to know what’s causing the fireworks.
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Re: Dead CamVac motor

Postby RogerS » 07 Aug 2019, 10:17

Woodster wrote:Oh dear, that doesn’t look good! Shame as Camvac make what are normally the quietest shop vacs on the market. It would be nice to know what’s causing the fireworks.


Hopefully Bob or Robert will be along soon !

Replacement motor is £100. A new twin motor Camvac is £300 including carriage
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Re: Dead CamVac motor

Postby 9fingers » 07 Aug 2019, 10:21

If that was with no earth connected then I assume there is a similar firework display on the other brush viewed from behind, I'd say it is terminal.
if you only have sparking from one brush then is suggests the brush is not completely free to slide in the holder or its spring is very weak. The latter often cause by over heating in the brush itself and thus softening the steel in the spring. one effect reinforces the other.

Aldi have a workshop vac for £50 instore and online at the moment. just sayin' :lol:

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Re: Dead CamVac motor

Postby RogerS » 07 Aug 2019, 10:30

9fingers wrote:If that was with no earth connected then I assume there is a similar firework display on the other brush viewed from behind, I'd say it is terminal.
if you only have sparking from one brush then is suggests the brush is not completely free to slide in the holder or its spring is very weak. The latter often cause by over heating in the brush itself and thus softening the steel in the spring. one effect reinforces the other.

Aldi have a workshop vac for £50 instore and online at the moment. just sayin' :lol:

Bob


You can see the other brush to the left and no sparking as bad as the rh one. Will have another look at the brush holder that is sparking badly.

I was also wondering about what looks like a glow at the bottom of the commutator ?
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Re: Dead CamVac motor

Postby RogerS » 07 Aug 2019, 10:33

9fingers wrote:....
Aldi have a workshop vac for £50 instore and online at the moment. just sayin' :lol:

Bob


I've got one of those permanently connected to the Kapex. No good for the table saw as that is large diameter...4" plus
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Re: Dead CamVac motor

Postby 9fingers » 07 Aug 2019, 10:35

Not sure about the glow, could be a reflection?

Is this test with no earth connected?

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