would you replace a stator with these readings?

[duaneage]

Well, my cats think the stator is bad. I put the stator in a Kroger bag and left it on my workbench and they peed all over it last night. Good grief.

Cats have better intuition than we do, part of that nine lives thing.

[don_gibb6512]

Test results.

With stator removed from the case cover, re-tested the resistance wire-wire and wire-ground: 3.64 ohms on all readings. Basically the same results as the prior two tests. For the sake of clarity, I'm going to refer to the wires as W1, W2 and W3.

Using a Variac Transformer http://www.variac.com/

W1-W2: up to 2.5 amps, meter reads 1.5v AC @ 60 cycles
W2-W3: up to 2.5 amps, meter reads 1.5v AC @ 60 cycles
W1-W3: just prior to 2.0 amps, current spikes blowing fuse in Variac

WOW!!! Short is confirmed. Wasn't expecting it to be so drastic, but yeah. I will also post an unusual picture of the stator poles. Three of them have damage to their surface which leaves me a bit concerned about clearance to the rotor surface.

Don

[tom203]

Test results.

With stator removed from the case cover, re-tested the resistance wire-wire and wire-ground: 3.64 ohms on all readings. Basically the same results as the prior two tests. For the sake of clarity, I'm going to refer to the wires as W1, W2 and W3.

Using a Variac Transformer http://www.variac.com/

W1-W2: up to 2.5 amps, meter reads 1.5v AC @ 60 cycles
W2-W3: up to 2.5 amps, meter reads 1.5v AC @ 60 cycles
W1-W3: just prior to 2.0 amps, current spikes blowing fuse in Variac

WOW!!! Short is confirmed. Wasn't expecting it to be so drastic, but yeah. I will also post an unusual picture of the stator poles. Three of them have damage to their surface which leaves me a bit concerned about clearance to the rotor surface.

Don

Well, I bet posplayr will rather explain this than the cat intuition stuff.

[don_gibb6512]

Anyone ever have this happen? Those were the only 3 poles with damage as far as I could tell. I'll look at them closer this evening with a magnifying glass and if weather permits, I'll inspect the rotor.

[bonanzadave]

Anyone ever have this happen?

Looks like the bike got dumped. Ground through the side cover .

[posplayr]

Well, I bet posplayr will rather explain this than the cat intuition stuff.

These results show the inherent problems with trying to perform unloaded tests on a stator. None of the tests that you perform using a simple VOM, are tests to positively confirm something is good. They can only be used to confirm something is bad.

For example, if you measure 70 volts AC on the stator open loop at 5K RPM you might think it is OK and the Stator is good, WRONG if it was also grounded the it would be bad. On the other hand if you measured only 25 volts, that confirms it is bad. So it can only verify a bad stator, leaving several possibilities on bad stators continuing to test good. Or a more often result is you are getting 70 volts, and there is also no short shown from the ohm meter. The you load the stator by pushing current through it, it heats a little pushes couple of oil molecules over and you have a short even though both the open loop voltage and resistance both supposedly passed.

The break down in insulation is not a simple relationship and it is a function of how much voltage you apply to the stator. An ohm meter test only applies a few volts and it may appear fine, but as soon as you raise the voltage the insulation breaks down and you have a short. The ohm meter just is not a good insulation breakdown test.

The best tests are loaded tests. That is why I modified the original stator pages phase 1 to measure the voltage drops at 5K rpm (full load) as they were originally only done at idle when there was little to any current being pushed to the battery.

The problem with doing loaded tests on the stator is you need some special AC test equipment like an oscilloscope or an AC current clamp; most people don't have these. Here is a reasonable alternative if it does what it says. BK are a reasonable economy brand of test equipment.

http://www.bkprecision.com/products/model/312B/mini-ac-milli-amp-clamp-meter-600a.html

You would basically clamp this onto one of the stator winding rev to 5K and note the AC current. Do the same think on all the phases and make sure they are balanced. I posted the average currents as a function of RPM in that Compufire SERIES R/R appraisal (both SHUNT and SERIES).

http://www.thegsresources.com/_forum/showthread.php?t=161397

SHUNT_vs_SERIES_RR_Compare_Tutorial

[don_gibb6512]

Looks like the bike got dumped. Ground through the side cover .

Good guess but that didn't happen here. I bought this stator new from Electrosport about 8 years ago and both bikes I've had this in were never in any accidents.

If the rotor turns out to be slightly worn down on one edge, will that effect it adversely in any way?

[duaneage]

Any contact in there is detrimental so I would suspect foreign objects stuck to the magnet and went for a quick ride in there. Smacking the poles can cause problems, especially if the pole cracks

Take a magnet to the underside and maybe check the pan.

[rustybronco]

The problem with doing loaded tests on the stator is you need some special AC test equipment like an oscilloscope or an AC current clamp; most people don't have these. Here is a reasonable alternative if it does what it says. BK are a reasonable economy brand of test equipment.

http://www.bkprecision.com/products/model/312B/mini-ac-milli-amp-clamp-meter-600a.html

You would basically clamp this onto one of the stator winding rev to 5K and note the AC current. Do the same think on all the phases and make sure they are balanced.

Jim, I think using one of those could produce erratic results.

I used a cheap HF inductive AC ammeter when testing the current draw on my air conditioner and unless I placed the wire in the same spot in the clamp and held away from the other leg, it produced differing results. that is not to say the BK clamp will do any worse or better than the HF, just stating the results I saw.

could it have been caused by the clamp opening being a lot larger than the one used with your scope?

just saying...

[posplayr]

Jim, I think using one of those could produce erratic results.

I used a cheap HF inductive AC ammeter when testing the current draw on my air conditioner and unless I placed the wire in the same spot in the clamp and held away from the other leg, it produced differing results. that is not to say the BK clamp will do any worse or better than the HF, just stating the results I saw.

could it have been caused by the clamp opening being a lot larger than the one used with your scope?

just saying...

I don't know, my current clamp was $500 so it is not likely that a $85 device will even come close.

At best we can test for consistency between the windings. Maintaining consistent spacing would probably be the most fruitful. Maybe putting a foam block with a slit inside of the clamp to maintain a consistent distance for comparing the windings.

[tom203]

I was worried we wouldn't make it to 100 replies!
Lots of the new cheapo multimeters measure ac current to 10 or 20 amps just like dc current readings- sticking the probes between the current path.( Most likely, the reading is based on 60 cycle,so I don't know how accurate it will be at 10 times that frequency.) I think That I would only do this test as a last resort.

[posplayr]

I was worried we wouldn't make it to 100 replies!
Lots of the new cheapo multimeters measure ac current to 10 or 20 amps just like dc current readings- sticking the probes between the current path.( Most likely, the reading is based on 60 cycle,so I don't know how accurate it will be at 10 times that frequency.) I think That I would only do this test as a last resort.

For an 18 pole stator (IIRC) the frequency is at RPM/10.
So 5000 RPM is 500 Hz AC. Reading of AC when designed for 60 hz is probably a crap shoot as it is undefined.

[raistian77]

These are the current meters I use. The 60amp meter terminates in a BNC connector for scopes, a BNC to bannana clip converter is needed.

The 60amp one is about 300.00 and the 200/2000 amp one is about 180.00

[posplayr]

These are the current meters I use. The 60amp meter terminates in a BNC connector for scopes, a BNC to bannana clip converter is needed.

The 60amp one is about 300.00 and the 200/2000 amp one is about 180.00

Have you ever tried to measure the stator current and current balance?

[tkent02]

For an 18 pole stator (IIRC) the frequency is at RPM/10.
So 5000 RPM is 500 Hz AC. Reading of AC when designed for 60 hz is probably a crap shoot as it is undefined.

But the error of the crap shoot would be even on all the wires right? We don't really care about the exact voltage, just that they are even? Wouldn't even need to be very precise at all, we are only looking for large differences?