testing a motor

[frank horton]

I have an as new washing machine...(literally just 5 cycles)....have known the machine from new....Mother inlaw.....
anyway......
plug it in switch on and straight away it trips the RCD......did this 3 times......
took off what panels I could to look for broken/chaffed shorted wires.....non found.....
so before the fourth try I unpluged the motor connections....now the RCD stays in.....
.......
have taken the motor off looking for burns etc.....found nothing.....no bad smells either.....
have tested with an ohm meter Fluke (not really sure what I'm looking for, the meter reads zero and beeps if the two probes are touched together) directley on the brush holders and no short, the figure on the meter was 4......
on the photo u will see the wire holder/connecter.....
so have tried the meter between each wire and earth and no dead short......all connecters read between 4 and 5......
what else can I look for.....
I do need another washing machine as the old one sounds like it ready to die.....
......
the red and the black wires go directley go to the brush holders...
2 yellows...is that a rev counter....?
the orange, blue and the 2 whites look like they go to extra windings.....
.........
lastley if I connected a live and neutral to the brush holders would that be ok...plus an earth wire for safety..?.....just to test....

many thanks......

 

[waddycall]

Could it be something else giving earth leakage and the motor firing up just pushes it over the edge? Had this with a “faulty” boiler that tripped the RCD. Customer was adamant it was the boiler but it turned out to be the washing machine!

 

[Melvyn Best]

I had problems with my old steam cleaner tripping ,took it to a local steam cleaner engineering company as I didn’t have time to sort it myself , they charged me loads and said it was sorted. Got back to the workshop, plugged it in and f¥€k still tripped . Ended up finding and sorting the problem , it was the motor full, and I mean full, of water

 

[Screwdriver]

if I connected a live and neutral to the brush holders would that be ok...plus an earth wire for safety..?.....just to test....

No. It's a universal motor. You would need to connect the field windings and rotor in series. Problem is, on no load they fly off at top speed. On the other hand, you could test it by using DC, much safer.

Generally speaking, I would not recommend playing with live mains. In any event, you should at the very least bolt it down before testing. When they set off, the torque can throw the motor across the room. Ask me how I know...

 

[Red'n'Black]

To test the insulation properly you need a Megger, a DMM only applies a few volts. But when you pull the connections to the motor, does the machine try to run the whole program? Most modern ones will sense a fault (motor has a built in tacho) and stop.

Last machine I looked at that tripped the RCD, the fault was in the heating element. (Was really obvious once it was pulled out, the casing was all corroded and split). The programmer only turns on the heat a minute or so into the cycle, so if it never got that far it would look ok.
Pull both wires off the element (and tape them up obvs) and see if it still trips. The programmer will give up trying to heat the water after 5 mins or so but by then you'll have your answer.

 

[Robert Weaver]

Have you tried testing for short to ground/chassis on the motor?
Using the meter on resistance, keep black on the chassis earth spade (in second picture just above the bearing mount) then probe all other wires. None should give a low resistance, proving none are shorting to ground. Also, spin the rotor while you do this to check for intermittent shorts.

The rotor looks like it's DC fed, and the stator has multiple poles which mean you can't simply power it up. DC on the rotor creates a permanent magnet, which is attracted to the sinusoidally stator field when that's controlled. Easy way of having variable speed and torque.

Edit:
Should have spent more time reading op's post. Nothing is shorting to ground, then something else is causing earth leakage. I'd trace the wires back to the control board, checking for chaffing etc then all other housed component. There are sometimes capacitors for timing the door release; this might have failed short circuit.

Ps, the yellow wires are speed sensor.

 

[eddie49]

Here's a diagram showing a brief test at full speed, with the field coils in series with the armature brushes, as Screwdriver suggested:

Washing Machine Motor Wiring Diagram

Washing Machine Motor Wiring Diagram: In order to be able to wire the washing machine motor or universal motor we will need a diagram called the washing machine motor wiring diagram ,this one can be used to wire this universal motor on 220v ac or dc just follow the same diagram.

www.instructables.com

 

[Seadog]

Pull both wires off the element (and tape them up obvs) and see if it still trips.

Tape the ends individually, do not tape them together

 

[p0689109]

Has the machine been standing idle for long as that can cause electrical problems especially if it has been in a shed or garage? There is signs of corrosion on the motor.

 

[Screwdriver]

I thought @Red'n'Black had nailed it with the heating element?? Seems the most likely issue with a machine that has been stood. A visual inspection might even show some rotten corroded item sitting in a puddle for years is the culprit.

 

[Red'n'Black]

Not saying for definite it's the heating element. But you have to look at the points where mains and water might come into contact. As well as the heater you have
The fill solenoid valve
The pressure switch used to sense water level
The drain pump

Are there any signs of a leak around any of these parts? (or the drum above the motor, for that matter).
Does it trip the RCD when you turn it on at the wall? When you turn it on at the front panel? When you start a wash cycle? Different parts of the machine will be live for each of these.

Can you borrow a Megger from somewhere to test the motor insulation? I had a table saw that tripped the RCD, it turned out to be the filter capacitor but it measured ok on a DMM.