Need Help!- single phase motor gone faulty...

[Numb Nut]

Geof - thanks for the explanation - I think I understood some bits of it. I'm not sure I have the brains or motivation for learning physics or electrical theory!

Meanwhile, I hooked up the capacitor to the multimeter and it read 24.9 uF which is pretty darn close to the rated value of 25 uF so I guess it's working just fine.

Incidently, inside the junction box there are 4 wires going inside the motor, these are from v1, v2, w1 and w2 and all of these wires have low resistance with each other which I find odd - for some reason I was expecting to find 2 separate coils.

[Geof]

If the electrical checks out try greasing the bearings, and look for rub marks on the rotor where it may have been touching the fields. When the bearings go sometimes there is enough slop that the rotor hits the field and it bounces around inside while it is running.

Physics is not that hard, at least at the introductory level and simple electrical theory can be very helpful when working with machinery; well worth the effort. It is also helpful to learn about forces and vectors and levers because this sort of thing comes in handy for moving machines and figuring out clamping on parts.

[Al_The_Man]

According to my reasoning, the connections could conform to the start winding between W2 & W1 and the run winding between V1 and V2, this would reverse the start winding WRT the run winding when the straps were swapped.
In that case there should be a separation between windings when the straps are removed, if you get continuity between the two, this could indicate a short between windings.
Al.

[Kipper]

Originally Posted by Numb Nut That diagram doesn't show the motor windings which are connected to the various points on the 6 terminals but you knew that, right? The motor plate states that the capacitor is 25uF / 450V. Anyway, it's time to get the capacitor out of the motor and hooked up to a multimeter in capacitance measuring mode. Oh yes. They always talk in the end...

Yeah....this numbnut just noticed the 6 posts and jumped to confusion

I had a "senior moment" possibly a "brainfart" or some such...

[Geof]

Originally Posted by Kipper .....I had a "senior moment" possibly a "brainfart" or some such...

Senior moment????? Bl***y H*** you have to wait at least another 22 years before you can use that excuse.

EDIT: But you do live in a nice part of the country now the Dark and Satanic Mills are no longer in operation.

[Kipper]

Originally Posted by Geof Senior moment????? Bl***y H*** you have to wait at least another 22 years before you can use that excuse. EDIT: But you do live in a nice part of the country now the Dark and Satanic Mills are no longer in operation.

It's been a while since you've been to Leeds Geof.....They started building skyscrapers here a year or so back......Bl**dy awful things! I rarely venture into the city centre....Nothing there except shops full of clothes gay bars and doorway urinals.....Not my kind of place.

I'll wait the 22 years before using the senior moment excuse...... I'll try "Transient intellectual block" for now

[Geof]

Originally Posted by Kipper It's been a while since you've been to Leeds Geof.....

First time was back in 1970 and it qualified as B awful then; most recent visit was 2004 but I just drove through. I spent four days there in 1996 attending a conference; it was much less B awful than 1970.

[Numb Nut]

Originally Posted by Al_The_Man According to my reasoning, the connections could conform to the start winding between W2 & W1 and the run winding between V1 and V2, this would reverse the start winding WRT the run winding when the straps were swapped. In that case there should be a separation between windings when the straps are removed, if you get continuity between the two, this could indicate a short between windings. Al.

I took the motor apart last night - absolutely no sign of damage - mechanical or electrical, nothing looked burnt or out of place.

As per Kipper's observation - there isn't a mechanical switch inside this motor.

I measured the wire resistances with the multimeter and with the terminal strips removed.

V1 - V2 = 8.8 Ohm
W1 - W2 = 8.8 Ohm
V1 - W1 = 6.3 Ohm
V2 - W2 = 8.9 Ohm
V1 - W2 = 7.5 Ohm
V2 - W1 = 7.7 Ohm

There's no discoloration of the windings which might indicate damaged windings - so it really does look that the windings are meant to be continuous like this.

Any more ideas?

[Al_The_Man]

The start winding has to be separate from the run winding in order to reverse, they are usually connected internally only when it is built for one direction.
It would appear you have a short between windings.
Al.

[Numb Nut]

Originally Posted by Al_The_Man The start winding has to be separate from the run winding in order to reverse, they are usually connected internally only when it is built for one direction. It would appear you have a short between windings. Al.

What you say makes perfect sense. The only thing is that it's hard to accept that the windings have gone faulty - the motor looks like new inside and out and hasn't had much use. I still haven't tried calling up the service and parts number but that's probably the next move.

[Al_The_Man]

It is possible that a short exists between windings and if the resultant current is not excessive you will not see any evidence in the windings.
If it is OK mechanically, Lets face it, there is not much left, after the capacitor is proved OK.
One thing to try is get hold of a clamp-on ammeter and test the current, also try it in the reverse direction.
Al.