GS Stator

[Brendan W]

I would expect thermal imaging systems to auto range for maximum contrast. The human eye frequency range is fixed and it will show white whether the top temperature in the view is an exhaust or a poorly insulated door on a house. Colours for effect and to show where to point the crosshairs for the messpunkt.
The casings and oil are taking away heat fairly fast so the true stator temperature could well be multiples of the indicated difference in the pictures.
BTW anyone notice that the sun was shining in one pic so the difference is more than you think
Then we already know that shunt types have higher average current in the stator and that integrated over a period should be enough to know considerably more energy is being dissipated in the windings and that for me is a more accurate measure than external imaging. In fact given the pathways for the heat to escape the stator, that there is any detectable difference at all on the outside is a strong indicator that there is a big temperature difference.

[posplayr]

Would it be correct to say that the rate of change of flux in the stator poles is what induces the emf in the windings. If you could somehow support all the windings in the rotor without a core the emf would be much less and that the stator poles saturate at some point making increases of speed and or number of windings irrelevant.

The simple way I like to think of it is that "current is produced in a wire when you move a wire through a magnetic field"(generator effect). Correspondingly "when you put current through a wire that is in a magnetic field a force is applied to the wire"(motor effect). The faster the velocity the more current/force, the higher the magnetic field the higher the current/force.

Generally speaking motors and generator designs try to minimize air gap because a much larger flux density (i.e. magnetic field) can be supported in the iron than in air. So a set of windings supported in air would be a very poor motor/generator. The rotor is so close to the stator to minimize air gaps and keep the magnetic field in the gap higher because there is less air. You can probably find a reference on line that will show the paths of flux for this type of generator.

If you want to talk about cutting lines of flux(wire moving through the magnetic field) or rate of change of flux (not sure what you are referencing here unless it is an AC machine), you are starting to get more into motor design principles that are probably beyond most folks here.



EDIT:
I found this link, apparently changing magnetic field also causes the voltage change. This is implicit in my statement that higher magnetic field produces higher current/force. The link talks about Maxwell, Faraday and Lentz all in the same context with not nary an integral so I think this is a good place to start for good understanding.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html

In an undergraduate (1st year Junior level) you take Electromagnetics I and that is where you have to cut your theeth on Maxwell's Equations including the integral and differential forms shown here.

https://en.wikipedia.org/wiki/Maxwell%27s_equations

[John Park]

I prefer Electrosport and with a Series R/R they are no problems. The GS1100E stators have been high quality like this one. Heavy epoxy to immobilize the winding. Most people probably do not realize that the are Electromotive forces on the winding which will cause flexure if not supported. A thermal epoxy as you see here is what is used. It is not just for insulation, it is to keep the winding from flexing under the EMF forces. If you see winding that do not appear to have anything but a thin insulation cover, they are going to be less tolerant to usage.


I don't know that all of Electrosport product coating are this heavy but there are superior to most I have seen from any other vendor. If you are still using Shunt R/Rs and burning stators well there is not much anybody can say to help...............

This picture was to document heat damage from a MOSFET Shunt R/R after a 250 mile ride on a brand new ES stator. It was getting hot.

I'm assuming that the brass fitting is an oil spray device. Is it a coincidence that the 'sautéed' section is directly in its path, or are we making an assumption that oil is cooling the stators? I've seen stators fried in a sectional area, but usually as a result of shorting directly to the core.

The stator shouldn't really see all that much oil, being inside a centrifuge. Hot oil as a cooling mechanism presupposes that the stator is hotter than the oil. The case is well drained and the only feed is from the main bearing spin off. I'd expect the flywheel to be above the oil level so all that normally gets to the stator is some transient splash which would be flung off pretty fast.

Or… it just got hot there because it did. And/or, the fitting is something else. ??

[posplayr]

Without a controlled experiment on a bench setup running at set speeds with a fixed load and a thermometer measuring precisely, we only have a guess as to what's going on.

There is far more already known than would be answered by the measurements you suggest and those measurements would likely do nothing to answer the naysayers on oil temperature drop using Series R/Rs.

[posplayr]

I'm assuming that the brass fitting is an oil spray device. Is it a coincidence that the 'sautéed' section is directly in its path, or are we making an assumption that oil is cooling the stators? I've seen stators fried in a sectional area, but usually as a result of shorting directly to the core.

The stator shouldn't really see all that much oil, being inside a centrifuge. Hot oil as a cooling mechanism presupposes that the stator is hotter than the oil. The case is well drained and the only feed is from the main bearing spin off. I'd expect the flywheel to be above the oil level so all that normally gets to the stator is some transient splash which would be flung off pretty fast.

Or… it just got hot there because it did. And/or, the fitting is something else. ??

Good eye on spotting the sprayer. I purposely avoided mentioning it as it would require going into more discussion really not relevant to the specific discussion of series R/R but more into the thermal properties of stators and how they cool themselves. The sprayer was added after the first 250 mile ride (on a new stator install) that burned the stator as shown, but before I found a Compufire Series R/R. I have since swapped out the stator using the Compufire and without the sprayer (I plug the line) and the stator is still baby blue. Overheating has been stopped

The sprayer was positioned to the 'sautéed' section" to keep it cool and after adding it seemed to lower the operating temperature of the oil and stop/reduce the burning. It aimed to spray into the air gap to get at the shrouded stator coils and not onto the rotor.

From the heating pattern it is clear (to me at least) that the lowest coils stay cooler due to oil picked up from the bottom of the cover. The coils at the top remain relatively dry or at least without much oil circulation.

Also when these little baby blue coils turn brown, my assumption it is because the thermal epoxy is getting over 400 degF which is a damn site hotter than the oil. My temps before the sprayer would run normally at about 270 degF as measured by teh OEM oil temp gauge. After fitting with the Compufire (and I have to admit teh sprayer in various forms). I'm hard pressed to get the engine to 230 degF with it remaining closer to 220 degF most of the time.

[posplayr]

Where I work we use a fair number of motors and differences in how the stator is wound and wire size have an effect on current consumption and performance in general. I don't know at what rpm the magnetic field is saturated on a GS charging system using various stators but I do know my bike sees a fair bit of time in the lower rpm regions, and if stators are burning up because of too much power being shunted back in themselves then what's the point in maximizing current output at a lower rpm when the system doesn't need it?

Everyone is free to do what they want but I don't see the point in high output stators unless you are driving electrical loads beyond the bike as stock. Every GS I've ever bought or owned had a stock stator and the charging system functioned okay after fixing R/R grounds in the system. Clearly though, a lot of stock stators burn out so there is value in fixing the wiring system and installing a series
R/R. My unofficial survey of stator failures has the chinese made aftermarket units (Electrosport and RM Stator) failing at a higher rate than stock or Rick's. That's why I spent the extra money on a Rick's recently. They make no claim about being high output and the quality seems good.

Ed if you are burning stator it is because of the R/R not the stators themselves. At best you can say one stator is more tolerant to the abuse of a SHUNT R/R than another. That doesn't necessarily mean the others are poor quality. However, I will propose that your best stator is based on the type of R/R you run. If it is SHUNT then teh electrosport is not the best choice. If you go series I think it is the best for reasons I already mentioned above.

[Nessism]

Also when these little baby blue coils turn brown, my assumption it is because the thermal epoxy is getting over 400 degF which is a damn site hotter than the oil. My temps before the sprayer would run normally at about 270 degF as measured by teh OEM oil temp gauge. After fitting with the Compufire (and I have to admit teh sprayer in various forms). I'm hard pressed to get the engine to 230 degF with it remaining closer to 220 degF most of the time.

Here we go again...

Figured this discussion would come around to this huge oil temperature reduction claim sooner or later. I'm not going to get into it again but have gone on the record having proven, with back to back testing, using both a shunt and series R/R on my bike, and it made no difference in oil temp.

[posplayr]

Here we go again...

Figured this discussion would come around to this huge oil temperature reduction claim sooner or later. I'm not going to get into it again but have gone on the record having proven, with back to back testing, using both a shunt and series R/R on my bike, and it made no difference in oil temp.

For your bike and your bike alone. Making categorical statements in the face of overwhelming evidence of multiple owners is something all together.

Anybody else following this, just go to the top of this link for other people (beside me)who have reported temperature drops. The bigger the engine the more drop is likely. It seems to be primarily liter bikes with BB kits (higher compression).

http://www.thegsresources.com/_forum/showthread.php?161397-Compu-Fire-SERIES-R-R-Install

Ed it must be a conspiracy...................... and your bike is in on it

[Nessism]

Jim, you must be an electrical guy because you don't know very much about heat transfer.

In order for the engine oil to heat up from 220 to 270F because of the stator then the stator must be significantly hotter than that. There is almost NO oil flow over the stator (oil jet nonsense notwithstanding) so the stator would have to be heated to something like 350+F to heat up a gallon of oil in the sump to 270F. You would need considerably more power than the extra stator power shunted back into itself to increase the stator temp that much.

I'm not getting into it any further since this is just more nonsense rehash. Go do a proper test like I did and report back with photo evidence like I did. Same bike, same day, 30 miles testing with each R/R back to back. Remove that oil spray nozzle first of course. I double dog dare you to do this test and report back. I did this exact test and it showed NO difference in oil temp.

[posplayr]

Jim, you must be an electrical guy because you don't know very much about heat transfer.

In order for the engine oil to heat up from 220 to 270F because of the stator then the stator must be significantly hotter than that. There is almost NO oil flow over the stator (oil jet nonsense notwithstanding) so the stator would have to be heated to something like 350+F to heat up a gallon of oil in the sump to 270F. You would need considerably more power than the extra stator power shunted back into itself to increase the stator temp that much.

I'm not getting into it any further since this is just more nonsense rehash. Go do a proper test like I did and report back with photo evidence like I did. Same bike, same day, 30 miles testing with each R/R back to back. Remove that oil spray nozzle first of course. I double dog dare you to do this test and report back.

Sorry Ed, there is really nothing worth sacrificing another set of WebCams to the stator gods for. The facts that exist tell the important story, I have too many other things to worry about that trying to put a finer point on what I already know today.

I will however update the power calculation that I published. Used a quality Fluke current probe (the raw data is published in the Compufire v.s. FH012A comparison back 2010)I measured the stator current in one of the legs and converted that to a three phase power equivalent of 26 amp RMS (all three phases).

In order to calculate the power, I used : P=I^2*R where R is assumed to be 1/2 an ohm(what you would measure at room temperature with an ohm meter). note 26^2/2=338 watts. If we scale the likely resistance based on a stator temperature of 400 degF which is what it takes to blacken the epoxy then R goes from about 0.5 ohms to 0.86 ohms which would now be 581 watts.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/restmp.html#c3

The question is what temp is your stator running at? It would also explain why my engine cooled from just spraying the stator with the MOSFET R/R.

The interesting conclusion which is supported by the theory is that the PM alternator is not a power limited device, it is a current limited device. If the output is regulated to 14.5V then there is no effective difference at the DC output. But when shunting the stator windings, you can not infer anything about stator power using Factory quoted power capability. Two completely different things.

Given a high enough RPM, the PM generator will push it's maximum current limited only by the magnetic saturation effects. If that current is going through a room temperature stator at 0.5 ohms (only at startup) it will dissipate less power. If the stator is at 400degF and has a resistance of 0.86 ohms expect 70% more power being dissipated.

[John Park]

One thing that occurred to me is that the oil flow to the cover would probably be considerably higher on a Twin because of the balance shaft bearing that dumps into the front of it. Whether that results in more oil getting to the stator is not assured, but it should help somewhat. It also adds a bit more heat sink to the cover as it's longer. It doesn't seem as though you would get the same high oil temps either, as the sump is pretty huge - 2.6-2.9 liters - and the pan area is more or less similar. I've done in a few stators on twins, but it took about 35,000 miles and usually a duff battery to do it.

As I understand it, the number of turns on a pole determines the voltage when the magnet is saturated. Basically like the output side of a transformer. I'm planning to rewind a stator soon, and had planned to go with three rows of ten [18ga] because that's what I've seen on stock stators, but since I spend almost no time in town and rarely below 4000 rpm I'm wondering if dropping that by ten percent would still give me enough idle voltage and put less strain on the system.

Is there a linear voltage/turns ratio at play or some other formula? How critical is wind number? Is there a 'right number'?

[Nessism]

In order to calculate the power, I used : P=I^2*R where R is assumed to be 1/2 an ohm(what you would measure at room temperature with an ohm meter). note 26^2/2=338 watts. If we scale the likely resistance based on a stator temperature of 400 degF which is what it takes to blacken the epoxy then R goes from about 0.5 ohms to 0.86 ohms which would now be 581 watts.

581 watts out of a GS charging system? Humm...

[posplayr]

581 watts out of a GS charging system? Humm...

Ed , You have not figured out from in yet huh?

if on the other hand you have anything to debate about the calculation lets hear it?

[posplayr]

One thing that occurred to me is that the oil flow to the cover would probably be considerably higher on a Twin because of the balance shaft bearing that dumps into the front of it. Whether that results in more oil getting to the stator is not assured, but it should help somewhat. It also adds a bit more heat sink to the cover as it's longer. It doesn't seem as though you would get the same high oil temps either, as the sump is pretty huge - 2.6-2.9 liters - and the pan area is more or less similar. I've done in a few stators on twins, but it took about 35,000 miles and usually a duff battery to do it.

As I understand it, the number of turns on a pole determines the voltage when the magnet is saturated. Basically like the output side of a transformer. I'm planning to rewind a stator soon, and had planned to go with three rows of ten [18ga] because that's what I've seen on stock stators, but since I spend almost no time in town and rarely below 4000 rpm I'm wondering if dropping that by ten percent would still give me enough idle voltage and put less strain on the system.

Is there a linear voltage/turns ratio at play or some other formula? How critical is wind number? Is there a 'right number'?

It is linear till it starts to saturate and a Lille more and it is maxed out no more current power limit; and yes the same physics for a transformer.

[Nessism]

Ed , You have not figured out from in yet huh?

if on the other hand you have anything to debate about the calculation lets hear it?

Well Jim, on my first 850 I wired the charging system with the R/R output line straight to the battery with a 15A fuse in-line. The bike ran fine this way until I decided to up rate to a 20A fuse just to be safe. Pretty sure my charging system isn't even getting halfway to your 581. Oh well, nevermind. I'm just an electrical heathen. You're doing the "new math" and this just doesn't compute in my head. My manual says "240 watts max output" from my charging system anyway so I'm good living where I am. You do as you like but my boat is staying right here.