Why Unloaded Stator tests are BAD.

[posplayr]

I have stated here before that doing any open loop stator tests with a Volt Ohm meter (VOM) are not conclusive . This is because the stator winding insulation is not being stressed to see if the insulation will break down at the higher voltage.

This means that the entire Phase B tests in the stator pages may or may not be correct unless you replace your ohm meter with a MEGGER.

EDIT 7/7/2013:
I just discovered that there are several available for very reasonable prices on Ebay.

Old school:
Silver Tone Resistance Measurement Tester Megger

http://www.ebay.com/itm/Silver-Tone-Resistance-Measurement-Tester-Megger-Megohmmeter-/321063607409?pt=LH_DefaultDomain_0&hash=item4ac0e1dc71

Digital :
VC60B+ Digital Insulation Resistance Tester Megger

http://www.ebay.com/itm/VC60B-Digital-Insulation-Resistance-Tester-Megger-MegOhm-Meter-USA-Seller/320898816590?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D163%26meid%3D8932750316131304155%26pid%3D100005%26prg%3D1088%26rk%3D2%26sd%3D321063607409%26

http://www.thegsresources.com/garage/gs_statorfault.htm

Doing unloaded tests (ohm meter with small current) /open loop tests (OL voltage) do not test what happens at full current when insulation break down can occur. These VOM tests can only prove a bad stator, not confirm a good one.

If you have something called a MEGGER you can do an conclusive open loop test; watch this video it shows a good test using the MEGGER with a high power mode; and a failed test using a low power VOM mode. So with small voltage OHM test the insulation did not break down and the test gives the wrong result.

http://www.youtube.com/watch?v=Fyd3S1EWfYA&feature=related

Since most people will not have a MEGGER, a good alternative but also definitive test is to test when the stator is producing full current and is shown to not break down the insulation using a AC current clamp. (i.e. measure stator leg current while running the engine at 5000 RPM)

You can now find cheap current clamps like the BK one below to do the test, you can test either the stator wire AC currents/voltages or you can also use it to measure DC output on the battery side of the R/R as well.

This is a BK model; there are some others for a similar price that have pretty descent specs if anybody is looking for an VOM upgrade.

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

There are others that are as good and perhaps even a little cheaper. Steve bought one for about $85 i think.

A quick tutorialon a clamping meter (for current measurements)

http://www.youtube.com/watch?v=m3dAFInO7i0&feature=related

This is a tutorial for using a current clamp attachment but the same applies to the current clamp meter. The 3 phase AC is going to be very similar to a GS stator.

http://www.youtube.com/watch?v=95vI-Xm3WHk&feature=related

PS: A MEGGER is just a Ohm meter that uses a large voltage to test the resistance rather than a much smaller one like a VOM would.

Here are some MEGGERS for just under $400; the clamping meter is a whole lot cheaper

http://www.tequipment.net/MeggerMIT230.html

for antique equipment buffs

http://physics.kenyon.edu/EarlyApparatus/Electrical_Measurements/Megger/Megger.html

[koolaid_kid]

Link doen't work, Jim.

[posplayr]

Link doen't work, Jim.

Sorry ; copied and pasted from another link should work now

[BassCliff]

Great information Jim!


I'll let your boss know that you don't have enough to do at work.



Thank you for your indulgence,

BassCliff

[posplayr]

Just takin a little break Cliff

[salty_monk]

There are several clamp meters on EBAY..... some are incredibly cheap shipped from HK some are US shipped & still in the $20 range.

Are these like an ordinary Multimeter in as much as a cheap $10 one will be nowhere near a Fluke in overall accuracy & ruggedness but for our purposes of occasional use likely be ok?

[Graham]

Most clamp-on meters are made for 60hz and may not read the amps correctly at 5000rpm. I ran into a similar situation with 3phase motor speed controls, some clamp-on meter wouldn’t read 100+hz. 5000rpm would be like 500hz wouldn’t it?

I did find that if you tested voltage from a stator lead to engine ground while running that a ground fault would show up even after an ohm test to ground passed.

I have seen stator lead-to-lead voltage test in the stator papers but I seem to have missed the stator lead-to-ground voltage test in them. Didn’t see a stator lead-to-ground test in the factory manual either.

[koolaid_kid]

Graham, a Hertz is 1 cycle per second, so to convert revolutions per minute to cycles per second just divide by 60.
5000/60 ~= 83 Hz. Still not 60 so the count would be off.

[pete]

Here's a question...

What about loading it up with high wattage resistors of a suitable value and measuring the voltage across the resistors with a normal multimeter?

No idea what value they should be, but just a thought...

I mention this because I intend to check mine tomorrow during its first start since the rebuild, and all I have available is a multimeter...

[Graham]

Graham, a Hertz is 1 cycle per second, so to convert revolutions per minute to cycles per second just divide by 60.
5000/60 ~= 83 Hz. Still not 60 so the count would be off.

I wasn’t sure of my math on the hertz. 18 poles divided 3 phases times 5000 RPM divided by 60 seconds gave me 500 cycles or hertz.

[Skateguy50]

I got an engineering degree and passed my fundamentals of engineering exam but I am pretty sure I got just over the minimum score on the electrical engineering part... I did a few tests on mine said the damn thing wouldn't charge the battery in the fall and I dont want to kill another battery so screw it.

Ordered a new stator from electrosport and a r/r kit from duaneage and called it a day

[Steve]

There are others that are as good and perhaps even a little cheaper. Steve bought one for about $85 i think.

This is the one that I got for $80 at Radio Shack. Click HERE for details.


I have only played with it a little bit, but it seems to be OK.
I got it with the hope of being able to check charging current and starter draw because this is one of very FEW clamp-on meters that will also measure DC amps.

.

[BassCliff]

I have seen stator lead-to-lead voltage test in the stator papers but I seem to have missed the stator lead-to-ground voltage test in them. Didn’t see a stator lead-to-ground test in the factory manual either.

Hi,

As I understand it, the stator "lead-to-ground" tests are passive, measuring for continuity only. You want to see NO continuity.


Thank you for your indulgence,

BassCliff

[posplayr]

I wasn’t sure of my math on the hertz. 18 poles divided 3 phases times 5000 RPM divided by 60 seconds gave me 500 cycles or hertz.

IIRC that is correct and what I have measured in teh past.

For an 18 pole stator The AC Frequency is 1/10 of the RPM

F_ac-Hz = RPM/10

5000 RPM==> 500 Hz

[bakalorz]

I have stated here before that doing any open loop stator tests with a Volt Ohm meter (VOM) are not conclusive . This is because the stator winding insulation is not being stressed to see if the insulation will break down at the higher voltage.

This means that the entire Phase B tests in the stator pages may or may not be correct unless you replace your ohm meter with a MEGGER.

http://www.thegsresources.com/garage/gs_statorfault.htm

Doing unloaded tests (ohm meter with small current) /open loop tests (OL voltage) do not test what happens at full current when insulation break down can occur. These VOM tests can only prove a bad stator, not confirm a good one.

If you have something called a MEGGER you can do an conclusive open loop test; watch this video it shows a good test using the MEGGER with a high power mode; and a failed test using a low power VOM mode. So with small voltage OHM test the insulation did not break down and the test gives the wrong result.

http://www.youtube.com/watch?v=Fyd3S1EWfYA&feature=related

So far so good; this part of your post is correct, a megger is indeed the gold standard for checking insulation breakdown.

Two additional points that should be mentioned here:

First; a megger can only find a coil to ground fault, it cannot find coil to coil faults or faults within a coil where one winding shorts to another.

Second: the test that Graham mentioned (engine running at 5000 rpm, Stator disconnected from R/R, AC voltage between ground and and a phase lead, check all three, one at a time) can work as kind of a poor mans megger and should be added to the troubleshooting.

Since most people will not have a MEGGER, a good alternative but also definitive test is to test when the stator is producing full current and is shown to not break down the insulation using a AC current clamp. (i.e. measure stator leg current while running the engine at 5000 RPM)

For the megger you found a video to explain it, do you have any kind of similar verification or justification for this statement or did you just pull it out of ... the air .

Because its not just wrong, ITS HARMFULLY WRONG, THIS IS POOR ADVUICE AND SHOULD NOT BE FOLLOWED, IT CAN CAUSE YOU TO CONCLUDE THAT A PERFECTLY FINE STATOR IS DEFECTIVE.

So why do I say this ...

You seem to think that while producing current the stator is more stressed than when not producing current, and in many senses that is true. However, when the stator is running open circuit (as in the AC tests currently in the stator papers) it is also under stress, but a different form of stress ... namely it is producing high voltage.

Guess which stress (high currents at ~14 volts) or (low current at 60+ volts) will find insulation breakdown ... here's a hint for you ... the megger (the gold standard) does high voltages at negligible currents (low enough current that it wont kill you if your workmates play tricks on you with a megger ... check you tube ...)

Now I'm sure you are not happy I made big red letters where I said that this test is potentially harmful, but it is potentially harmful, and its important, which is why I highlighted it.

Your test WILL (not maybe, but absolutely positively will) cause anyone who has a perfectly fine stator and a perfectly fine Suzuki OEM regulator to conclude that the stator is defective.

Pop quiz ... now that you've been given a hint, can you see why that would happen.

So in conclusion we can see:
Your suggested test is actually less effective than the test already in the stator papers.
It need an additional (not inexpensive) piece of test gear.
It WILL give incorrect conclusions to anyone with an OEM Suzuki R/R.


So are there any reasons to use it? Yes, as an additional optional test it could be occaisionally but rarely useful, mainly in that if one of the coils is able to move slightly, and shorts out when it does, this behavior will show up when the stator is producing current.

You can now find cheap current clamps like the BK one below to do the test, you can test either the stator wire AC currents/voltages or you can also use it to measure DC output on the battery side of the R/R as well.

This is a BK model; there are some others for a similar price that have pretty descent specs if anybody is looking for an VOM upgrade.

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

There are others that are as good and perhaps even a little cheaper. Steve bought one for about $85 i think.

A quick tutorialon a clamping meter (for current measurements)

http://www.youtube.com/watch?v=m3dAFInO7i0&feature=related

This is a tutorial for using a current clamp attachment but the same applies to the current clamp meter. The 3 phase AC is going to be very similar to a GS stator.

http://www.youtube.com/watch?v=95vI-Xm3WHk&feature=related

PS: A MEGGER is just a Ohm meter that uses a large voltage to test the resistance rather than a much smaller one like a VOM would.

Here are some MEGGERS for just under $400; the clamping meter is a whole lot cheaper

http://www.tequipment.net/MeggerMIT230.html

for antique equipment buffs

http://physics.kenyon.edu/EarlyAppar...er/Megger.html

My conclusions are quite different than yours:

I think that all the tests currently in the stator papers should stay as they are.

The test Graham mentioned should be added. (with a mention to use a megger instead if available)

Also should be added: reconnect the stator as normal, drive the bike for 20 minutes to get everything good and hot, and then repeat all the above tests while the stator is hot. THIS is something that will actually help chase intermittent failures.

If you want to add your test as an optional: Its a low probability shot, and not as effective as the open circuit AC test; but sure, fine, add it, you might occaisionally catch something ...
BUT THE AC TEST STAYS PRIMARY ... and if you add your test, make DAMN SURE that there is a big warning next to it that THIS TEST DOES NOT WORK WITH SUZUKI OEM R/Rs

Flame away ...