Applause

"Ed Sirett - Property maintainer and registered gas fitter." ;-)

Ed said "In a place I run, the damp pump windings have gone short
circuit (4.4 Ohms @ 3V DC)"

Well the 'winner' in that the 'fault' causing the clicky thing under
the stairs to do it's thing *seems* to be the wachine machine main
motor?

Firstly I'd like to mention that I wasn't 100% correct with my first
fault description in that the machine was infact 'On' but the door was
open (I assumed nothing much would be live in there in this state).
With the machine off and the power on, all was fine.

So, had a clean up in there (mainly belt rubber) and no sign of wet,
mice, purple worms or currents (flowing in any direction).

I then gleaned a general connection path, removing and testing the
connectors to various mains connected loads (and testing in-between)
till I came to the main motor. With that disconnected the machine did
everything else perfectly (but my whites weren't getting white, Doh!)
;-(

I pulled the motor and measured 45.5k ohms between either stator
winding end and ground and 1.6 ohms across it?

So, at 45.5 it's not a 'short' to ground so what else would cause that
sort of resistance (the 'breaking down' of a winding insulation
possibly?).

Q1, is there anything *I* can do about that? (strip the motor and
clean it with something (if so what?). Spray it with WD40 (that fixes
everything, right? g)

Q2, (and assuming the answer to Q1 is yes). Is 1.6 ohm 'ok' for a
stator winding (the wires are pretty thick)?

Q3, could someone tell me if an RCD cares if the current through the
live must come back through the neutral or the earth? Ti m runs away
zig zagging ;-)

All the best and thanks again to all for the replies (I actually read
them all so that makes me the saddest of all of us!)

T i m

p.s. Sorry if I missed anyone else mentioning a possible motor fault
(I did check / isolate / rule-out filters / caps where possible as
well ta .

T i m wrote:

Q3, could someone tell me if an RCD cares if the current through the
live must come back through the neutral or the earth?

I could - but you'd have to promise never, NEVER to tell anyone else ;-)

On Sun, 16 Jan 2005 15:30:15 +0000, Stefek Zaba
wrote:

T i m wrote:

Q3, could someone tell me if an RCD cares if the current through the
live must come back through the neutral or the earth?

I could - but you'd have to promise never, NEVER to tell anyone else ;-)

Ok, I won't .. just whisper it then ..

T i m ;-)

T i m wrote:
On Sun, 16 Jan 2005 15:30:15 +0000, Stefek Zaba
wrote:

T i m wrote:

Q3, could someone tell me if an RCD cares if the current through the
live must come back through the neutral or the earth?

I could - but you'd have to promise never, NEVER to tell anyone else ;-)

Ok, I won't .. just whisper it then ..

The RCD measures the current flowing in live and neutral.
If these differ by more than the set point (often 30/100mA) the RCD shuts
off the current in a specified time (often 20ms).
If the motor you have measures 45K from live-earth, then it may well exceed
the trip point, though a naive calculation would only lead to 240/45000 =
5.3mA, it may well not be a perfect resistor.

First, if it's in a washing machine, it may have gotten wet.
The first thing I'd try is to put it in an oven at 100C for 2 hours.

(on a tray, not touching the bottom of the oven).

If this cures it, as the water is likely to be dirty, you really should
wash the motor.
Dissasemble, remove bearings, wash with hot soapy water, rinse with hot water,
and air dry.
Examine bearings to see if any water has gotten in them.
If it has, they really need replaced.

If it's not improved after baking, then it's probably a film of carbon/grease
from the brushes and environment shorting to the case, or an overheated bit
on a winding where the insulation is breaking down.
You need to find and remove it by scraping/...

On 16 Jan 2005 18:05:54 GMT, Ian Stirling
wrote:

T i m wrote:
On Sun, 16 Jan 2005 15:30:15 +0000, Stefek Zaba
wrote:

T i m wrote:

Q3, could someone tell me if an RCD cares if the current through the
live must come back through the neutral or the earth?

I could - but you'd have to promise never, NEVER to tell anyone else ;-)

Ok, I won't .. just whisper it then ..

The RCD measures the current flowing in live and neutral.
If these differ by more than the set point (often 30/100mA) the RCD shuts
off the current in a specified time (often 20ms).
If the motor you have measures 45K from live-earth, then it may well exceed
the trip point, though a naive calculation would only lead to 240/45000 =
5.3mA, it may well not be a perfect resistor.

And that was only at 9V or whatever my DMM uses .. one assumes that
could get worse at 300V AC ?

First, if it's in a washing machine, it may have gotten wet.
The first thing I'd try is to put it in an oven at 100C for 2 hours.

I don't think it's been wet (as in leak etc) but it could have been in
a fairly high humidity (it's near the bathroom, tumble dryer (although
that's externally vented) and kitchen (her steamer). Mind you it's
been like that for a good few years now (~10) ?

(on a tray, not touching the bottom of the oven).

Understood.

If this cures it, as the water is likely to be dirty, you really should
wash the motor.
Dissasemble, remove bearings, wash with hot soapy water, rinse with hot water,
and air dry.

Ok, I was about to ask why you would dry it out then to wash it but
the first stage is a test ..

Examine bearings to see if any water has gotten in them.
If it has, they really need replaced.

Again, not 'water' .. and the bearings feel very smooth etc ..

If it's not improved after baking, then it's probably a film of carbon/grease
from the brushes and environment shorting to the case, or an overheated bit
on a winding where the insulation is breaking down.

Ok, well the brushes only have about 1.5mm of 'spring' left in them so
I dare say there is a lot of carbon around. I didn't know if washing
in something like white spirit / parrafin would be ok?

You need to find and remove it by scraping/...

Ok .. any cleaning / testing effort has got to be better than £200 for
a new motor ..(well, within reason) ;-(

All the best Ian .. ;-)

T i m

"T i m" wrote in message
...
Applause

"Ed Sirett - Property maintainer and registered gas fitter." ;-)

Ed said "In a place I run, the damp pump windings have gone short
circuit (4.4 Ohms @ 3V DC)"

Well the 'winner' in that the 'fault' causing the clicky thing under
the stairs to do it's thing *seems* to be the wachine machine main
motor?

Firstly I'd like to mention that I wasn't 100% correct with my first
fault description in that the machine was infact 'On' but the door was
open (I assumed nothing much would be live in there in this state).
With the machine off and the power on, all was fine.

So, had a clean up in there (mainly belt rubber) and no sign of wet,
mice, purple worms or currents (flowing in any direction).

I then gleaned a general connection path, removing and testing the
connectors to various mains connected loads (and testing in-between)
till I came to the main motor. With that disconnected the machine did
everything else perfectly (but my whites weren't getting white, Doh!)
;-(

I pulled the motor and measured 45.5k ohms between either stator
winding end and ground and 1.6 ohms across it?

So, at 45.5 it's not a 'short' to ground so what else would cause that
sort of resistance (the 'breaking down' of a winding insulation
possibly?).

I'd want to see at least 5 Meg but preferably 100 Meg to infinity so your
winding insulation is down and the motor in all probability has "had it".
The cause could be waqter causing an initial tracking over then a burnt
track remaining.
What did you measure it with by the way? A megger will show up these sort of
faults far better than an ohm meter but should be used with care if
electronics are involved

Q1, is there anything *I* can do about that? (strip the motor and
clean it with something (if so what?). Spray it with WD40 (that fixes
everything, right? g)

You could try slowly drying it out but like as not it won't be any good
afterwards anyway


Q2, (and assuming the answer to Q1 is yes). Is 1.6 ohm 'ok' for a
stator winding (the wires are pretty thick)?

Could be it reactance/impedance that matters here but if your windings
insulation is down to earth its immaterial

Q3, could someone tell me if an RCD cares if the current through the
live must come back through the neutral or the earth? Ti m runs away
zig zagging ;-)

Shhhhh its a secret

T i m wrote:
On 16 Jan 2005 18:05:54 GMT, Ian Stirling
wrote:

T i m wrote:
On Sun, 16 Jan 2005 15:30:15 +0000, Stefek Zaba
wrote:

T i m wrote:

Q3, could someone tell me if an RCD cares if the current through the
live must come back through the neutral or the earth?

I could - but you'd have to promise never, NEVER to tell anyone else ;-)

Ok, I won't .. just whisper it then ..

The RCD measures the current flowing in live and neutral.
If these differ by more than the set point (often 30/100mA) the RCD shuts
off the current in a specified time (often 20ms).
If the motor you have measures 45K from live-earth, then it may well exceed
the trip point, though a naive calculation would only lead to 240/45000 =
5.3mA, it may well not be a perfect resistor.

And that was only at 9V or whatever my DMM uses .. one assumes that
could get worse at 300V AC ?

If it measures 45K at 9V (more probably 3 IIRC), then if it was a perfect
resistor, you'd see about 5.3mA at 240V.
However, dirt generally does not form a good resistor, and will often
have a much lower resistance at high voltage.
snip
Ok, well the brushes only have about 1.5mm of 'spring' left in them so
I dare say there is a lot of carbon around. I didn't know if washing
in something like white spirit / parrafin would be ok?

Yes, but don't get any on the bearings.
You need to find and remove it by scraping/...

Ok .. any cleaning / testing effort has got to be better than ?200 for
a new motor ..(well, within reason) ;-(

All the best Ian .. ;-)

Motors can actually be quite reasonable, for some devices.
http://www.cpc.co.uk/ is worth a look.

Also, when you clean, if you find any burnt plastic
where the current is running, you should scrape it off to clean plastic.

On 16 Jan 2005 19:13:53 GMT, Ian Stirling
wrote:


And that was only at 9V or whatever my DMM uses .. one assumes that
could get worse at 300V AC ?

If it measures 45K at 9V (more probably 3 IIRC), then if it was a perfect
resistor, you'd see about 5.3mA at 240V.

You could be right re the ohms test voltage. I used a little (Maplin)
DMM. Just a minor point of detail. Assuming a resistance
breakdown issue wouldn't 300V be a more realistic voltage for these
issues. I mean the peak to peak being ~300 (240 RMS) and assuming a
resister would react (as in conduct phase voltage / current to ground
in this case) very fast the 300 could be more relevant (ie it might be
ok at 250 but fail at 300?) .. after all .. we aren't looking at power
here are we .. Just thinkig out loud .. ;-)

However, dirt generally does not form a good resistor, and will often
have a much lower resistance at high voltage.
snip
Ok, well the brushes only have about 1.5mm of 'spring' left in them so
I dare say there is a lot of carbon around. I didn't know if washing
in something like white spirit / parrafin would be ok?

Yes, but don't get any on the bearings.

Ok. I can probably strip the whole lot down to it's core components ..
clean bits as needed and re-assemble / lubricate etc.

Motors can actually be quite reasonable, for some devices.
http://www.cpc.co.uk/ is worth a look.

Just had a look on the net .. a new Zanussi for ~ £200 (not that we
have that 'spare' but potentially it would make more sense than
spending say £100 on a new motor)

Also, when you clean, if you find any burnt plastic
where the current is running, you should scrape it off to clean plastic.

It looks like new on the outside The inside is very good. There is a
little surface rust on the inside of the chassis base and that's about
it? . No water splashing about, no leaky pipes, no corroded connectors
or melted anything (if you took the pump out pump out it woud look
like new). I fitted new bearings and inner drum seal a few years ago
(bearing went) for about 30 quid the lot. A new 'spider' (with
bearings / seal) was over 100 pounds!

The motor is a bit dusty (rubber / carbon mix) but the windings you
can see are as new and there is no 'burnt shellac' smell at all?

I think this machine was designed when they were 'made to last' (and
made in Germany' possibly unlike some of the lower end AEG models
(made by Zanussi) at the time? (I have loads of Zanussi stuff and it's
also fine)

All the best ..

T i m

On Sun, 16 Jan 2005 19:01:39 +0000 (UTC), "John"
wrote:


I pulled the motor and measured 45.5k ohms between either stator
winding end and ground and 1.6 ohms across it?

So, at 45.5 it's not a 'short' to ground so what else would cause that
sort of resistance (the 'breaking down' of a winding insulation
possibly?).

I'd want to see at least 5 Meg but preferably 100 Meg to infinity so your
winding insulation is down and the motor in all probability has "had it".

Oh dear ;-( I gussed that with windings that size there was no way
45k could be a genuine windings resistance. But the brush holders are
quite big and unburnt and made no difference to the readings even when
removed (and underneath is's all clean and tidy) This motor is nearly
the same size as the one on my Myford ML10 lathe!

The cause could be waqter causing an initial tracking over then a burnt
track remaining.

I'm not sure if it's ever been wet in it's life (there is a pretty
good cover round most of it) and I can't see much that could get
'burnt / tracked (not saying there isn't of course) ;-)


What did you measure it with by the way?

Just a little DMM?

A megger will show up these sort of
faults far better than an ohm meter but should be used with care if
electronics are involved

Nope, the motor is loose on the kitchin top as we speak and is 'just'
the motor (stator, rotor, brushes and multipole connector).

Q1, is there anything *I* can do about that? (strip the motor and
clean it with something (if so what?). Spray it with WD40 (that fixes
everything, right? g)

You could try slowly drying it out but like as not it won't be any good
afterwards anyway

Hmm, I feel I'd like to clean all the dust out of it first and then
wash it with something 'solventy' but not too strong that might damage
the insulation any further? Maybe 'Gunk' followed by some warm soapy
water and a rest in front of the fan heater / oven etc (for both me
and the motor g) ? I even wondered if it might be worth having it
rewound?


Q2, (and assuming the answer to Q1 is yes). Is 1.6 ohm 'ok' for a
stator winding (the wires are pretty thick)?

Could be it reactance/impedance that matters here but if your windings
insulation is down to earth its immaterial

Understood .. so little to loose by trying to clean it up either?

Q3, could someone tell me if an RCD cares if the current through the
live must come back through the neutral or the earth? Ti m runs away
zig zagging ;-)

Shhhhh its a secret

Doh! ;-)

Cheers John ..

T i m

the current on the neutral must be the same as the live
thats how an RCD works , if there is an inbalance it trips .

T i m wrote:
On 16 Jan 2005 19:13:53 GMT, Ian Stirling
wrote:


And that was only at 9V or whatever my DMM uses .. one assumes that
could get worse at 300V AC ?

If it measures 45K at 9V (more probably 3 IIRC), then if it was a perfect
resistor, you'd see about 5.3mA at 240V.

You could be right re the ohms test voltage. I used a little (Maplin)
DMM. Just a minor point of detail. Assuming a resistance
breakdown issue wouldn't 300V be a more realistic voltage for these
issues. I mean the peak to peak being ~300 (240 RMS) and assuming a
resister would react (as in conduct phase voltage / current to ground
in this case) very fast the 300 could be more relevant (ie it might be
ok at 250 but fail at 300?) .. after all .. we aren't looking at power
here are we .. Just thinkig out loud .. ;-)

I was talking about the calculations for an ideal resistor.
The conventional way to measure current is RMS, 240VAC and 240VDC
will cause the same RMS (root mean square) current, and the same
heating in a resistor.
The numbers work just the same for milliwatts, and gigawatts.

However, dirt generally does not form a good resistor, and will often
have a much lower resistance at high voltage.
snip
Ok, well the brushes only have about 1.5mm of 'spring' left in them so
I dare say there is a lot of carbon around. I didn't know if washing
in something like white spirit / parrafin would be ok?

Yes, but don't get any on the bearings.

Ok. I can probably strip the whole lot down to it's core components ..
clean bits as needed and re-assemble / lubricate etc.

Motors can actually be quite reasonable, for some devices.
http://www.cpc.co.uk/ is worth a look.

Just had a look on the net .. a new Zanussi for ~ ?200 (not that we
have that 'spare' but potentially it would make more sense than
spending say ?100 on a new motor)

Also, when you clean, if you find any burnt plastic
where the current is running, you should scrape it off to clean plastic.

It looks like new on the outside The inside is very good. There is a
little surface rust on the inside of the chassis base and that's about
it? . No water splashing about, no leaky pipes, no corroded connectors
or melted anything (if you took the pump out pump out it woud look
like new). I fitted new bearings and inner drum seal a few years ago
(bearing went) for about 30 quid the lot. A new 'spider' (with
bearings / seal) was over 100 pounds!

The motor is a bit dusty (rubber / carbon mix) but the windings you
can see are as new and there is no 'burnt shellac' smell at all?

A usefull thing to do might be to keep measuring the resistance as you
clean it.

On 16 Jan 2005 21:56:24 GMT, Ian Stirling
wrote:

T i m wrote:
On 16 Jan 2005 19:13:53 GMT, Ian Stirling
wrote:


And that was only at 9V or whatever my DMM uses .. one assumes that
could get worse at 300V AC ?

If it measures 45K at 9V (more probably 3 IIRC), then if it was a perfect
resistor, you'd see about 5.3mA at 240V.

You could be right re the ohms test voltage. I used a little (Maplin)
DMM. Just a minor point of detail. Assuming a resistance
breakdown issue wouldn't 300V be a more realistic voltage for these
issues. I mean the peak to peak being ~300 (240 RMS) and assuming a
resister would react (as in conduct phase voltage / current to ground
in this case) very fast the 300 could be more relevant (ie it might be
ok at 250 but fail at 300?) .. after all .. we aren't looking at power
here are we .. Just thinkig out loud .. ;-)

I was talking about the calculations for an ideal resistor.
The conventional way to measure current is RMS, 240VAC and 240VDC
will cause the same RMS (root mean square) current, and the same
heating in a resistor.
The numbers work just the same for milliwatts, and gigawatts.


Indeed .. but I was thinking more along the lines of something
'breaking down' where the peak voltage may be more relavent than the
RMS? (I know it's just terms in this case .. an AC (sibe wave) having
RMS value of 240V *will have* a peak of ~300v etc. I was thinking if
you were to conduct a breakdown voltage test by applying a constant
(not alternating) voltage and slowly raising it till breakdown point
ocurred ... if you get me drift)

The motor is a bit dusty (rubber / carbon mix) but the windings you
can see are as new and there is no 'burnt shellac' smell at all?

A usefull thing to do might be to keep measuring the resistance as you
clean it.

Good idea .. ;-)

I really can't see why something as substantial as this motor could
'break down' other than by:

1) The gradual deterioation of the insulation on the windings
(vibration, expansion / contraction, heat, time).

2) Damage to the windings by intrusion by a foriegn object (loose
screw, mouse etc) or pressure on a sharp object (motor laminations
etc).

I can see how you could easily have option 1) and get 45k ohms but i
would have thought 2) would give a short cct or intermittent low
resistance?

Maybe I'll put the motor in a warm dry place tonight and measure it
again in the morning ..?

All the best ..

T i m

On Sun, 16 Jan 2005 21:41:39 +0000, Tony
wrote:


the current on the neutral must be the same as the live
thats how an RCD works , if there is an inbalance it trips .

No, ssshhh Tony ... !

T i m

what are you saying tim??

On Tue, 18 Jan 2005 23:12:24 +0000, Tony
wrote:


T i m Wrote:
On Sun, 16 Jan 2005 21:41:39 +0000, Tony
wrote:
-

the current on the neutral must be the same as the live
thats how an RCD works , if there is an inbalance it trips .-

No, ssshhh Tony ... !

T i m
what are you saying tim??

You may have missed the other trread and I didn't really want to start
that up again (how RCD's do or don't work..) so my question was
tounge-in-cheek .. ;-)

All the best ..

T i m