1.7kw motor testing

[studentspark]

What are the little coils with cable wrapped around them?

This motor is totally dead.
Power is getting to it but nothing works
What could have gone wrong with it and what testing would confirm the fault

Not really sure what readings I should be getting for the resistance of the windings, but the winding to the case is >299mohms


View media item 76470 View media item 76471

Thanks

 

[RF Lighting]

They are torroid coils used purely for RFI supression, and have no direct effect on the running (or not) of the motor.

Do you get any reading at all end to end on the coil?

Assuming it doesn't look like the coils have over heated, then first of all check the brushes haven't work out, and that the contact surfaces between them and the rotor is fairly clean.

Also if there is a capacitor connected to the motor, check that is functioning properly too.

 

[jj4091]

And is that a pressure switch at the bottom or just a terminal block?

 

[ericmark]

The testing of a brushed motor like this involves using tools like a growler but the normal quick test is to measure ohms and manually revolve the motor in all positions you should get similar reading.

With brushed motors one of the problems is when the brushes wear to the limit it can damage the commutator. Better motors have a bit of plastic on a spring embedded into the brush and when it wears to this point the plastic pushes the brush off the commutator so preventing damage worth testing you have connection. Brush and com easy to reach so easy to test.

 

[studentspark]

Thanks

end to end was 2.5ohms

Tried to test little capacitor but not sure how to test these. I got open circuit when testing. Have not got a multimeter that does capacitance


The connection from the switch was like a two pronged connection which feed the capacitor and the motor, so even if capacitor was shot power would still get to the motor

Turned the rotor and tested all gave equal readings about 1.8 ohms.

Motor looks clean and no sign of damage. Its hardly been used.

It did seem to pulse a bit though

 

[RF Lighting]

Have you checked the brushes for wear?

 

[Nozzle]

Tried to test little capacitor but not sure how to test these. I got open circuit when testing. Have not got a multimeter that does capacitance

Capacitor = no conduction of DC (once charged)
Capacitor = looks like a resistor to AC - the higher the frequency, the smaller the apparent "resistance"

When testing on a multimeter, chuck it on ohms and measure it out of circuit, and you should see it start off small and get larger up to the point it is fully charged when it'll show the highest "resistance". What you're really measuring is volts across the capacitor as it charges from the battery in the meter.

If the capacitor "resistance" doesn't change and starts off large the capacitor isn't charging as it has a broken connection.

How have you wired the field and rotor windings? What supply are you using? (It could be a universal motor, which works AC or DC). Don't forget to play safely and also use fuses to protect your supply.

Nozzle

 

[GNServices]

What you're describing sounds odd,
If there is 2.5ohms end to end and you have a supply across it, you would expect it to do something (buzzing etc).

Is it 230v AC?
Have you tried testing if it spins freely? If it doesn't, try to remove the "load" what looks to be some sort of pump, then try to run.
Have you tried to measure if current is flowing through it? (a clip on ammeter over the line conductor or ammeter in series with line conductor).

Is it buzzing or anything? If not and you are getting end to end resistance of 2.5ohms then it sounds like the rotor isn't reacting with the stator field.
Whether that be the either stator field has gone or the armature windings have gone/shorted (id say least likely).

I'd test each field winding first, they should be of equal value.
See annotation below;

Untitled

• GNServices
• 26 Apr 2014
• 1

 

[GNServices]

Tried to test little capacitor but not sure how to test these. I got open circuit when testing. Have not got a multimeter that does capacitance

Capacitor = no conduction of DC (once charged)
Capacitor = looks like a resistor to AC - the higher the frequency, the smaller the apparent "resistance"

When testing on a multimeter, chuck it on ohms and measure it out of circuit, and you should see it start off small and get larger up to the point it is fully charged when it'll show the highest "resistance". What you're really measuring is volts across the capacitor as it charges from the battery in the meter.

If the capacitor "resistance" doesn't change and starts off large the capacitor isn't charging as it has a broken connection.

Nozzle

True, however, at this point, it is worth to mention for the OPs benefit that this capacitor isn't required for the operation of the motor. I believe it is acting as a suppressor/filter, you can remove it from circuit if you wanted and try run the motor then from the wires that the capacitor was connected to.