GS Stator

[posplayr]

Hi I'm new here . I have been using the very informative site to better understand my 1981 GS750EX. Although I just bought the bike a week ago, and it is running fine, I have seen that it has previously had a small melt down. I originally thought that some bare wires were ground wires but now realize they are melted wires.

I ordered a new Electrosport regulator but did a little research into the electronics operation before doing that. While I do have a MS degree in Electrical Engineering, power electronics is not my specialty but some things jump out at me immediately about the charging design. It is way too simple!!!

Overall the combination of the permanent magnet stator with simple SCR shunt regulator will work but are suseptiable to upsets in load or bad connection issues. If it fails then you are likely to fry everything else on your bike with uncontrolled overvoltage conditions. The other main problem I see is that the simple generator can not be controlled because it is permanent magnet. If there was a field winding then the electromagnet could be controlled to reduce the generator output when not needed.

Since the generator output can't be controlled the voltage is basically proportional to the RPM and has to go somewhere. The SCR shunt regulator is a pretty scary way of controlling the output.
Without going into details I decided to at least upgrade the regulator which should eliminate a lot of the potential problems. The original linear regulator design is about as simple as you can make it and is probably way to simple for the real world.

I hope that the Electrosport is better designed although it might be asking to much to have a more advanced switching regulator.

Below are some links I found to describe the the three phase generator and the difference between Delta and Wye configurations. In "3 Phase Basics", formulas are provided and also shows that the Delta produces power in higher current but lower voltage that the Delta. I know these two different configurations were discussed in the Stator tutorial comments.


http://www.fieldlines.com/story/2003/9/11/84741/6758


http://www.windstuffnow.com/main/3_phase_basics.htm

Cheers

 

[Redman]

Pos,

Yes, your observations are correct.

I don't have MS in EE, but do have BS from 30 years ago, and years of troubleshooting industrial enquipment controls.

Biggest problem is if the R/R is not well grounded. Typically (on the Gs that I have, dont speciffically know about Es but would think are the same) the R/R is "Grounded" to battery box, and there is a ground wire from wiring harness connected to the battery box, but battery box itself may not be well grounded to the frame. IF the battery box ground to frame gets worse, then all the current the R/R is dumping to ground ("shunting" as you say) has to go thru the ground wire in harness, and then that ground wire in the wiring harness becomes a toaster wire burning not only itself but nearby wires in the harness, till that ground wire burns open, and then the R/R has no ground and voltage is then unregulated and goes high and then causes other problems.

So now that you know all this and understand all this, here is the practical advice of what to do about it: Add an additional "ground" wire from the R/R negitive (blk wire or the R/R case) to the battery negitive.

.

 

[davewallen]

Gee, for you EE guys, here's a question for you...

Can you wire an extra r/r in parallel with the first, as long as you keep the ground separate? I was considering this as a possible option to power accessories.

 

[PAULYBOY]

pos, if you have the electrical expertise to accurately identify the inherent weakness of the system right off the bat, and not from being a victim of it, is there anyway you could develop an alternative system that is more bulletproof without being more expensive. something with an easy to understand, illustrated, step by step tutorial? you know how much we'd be indebted to you, and maybe you could even make some money with it?
when my college kid son 1st got his gs450, and i accidentally stumbled over all this bad grounding mess in a last ditch poor mans attempt at getting his bike going again, not to mention now facing it on my own gs850, i didn't sign on for finnicky. i want a bike that rides well by just being tuned, fluids changed, and minimal down time. the last bike i owned was an old 81 yammy 920 some 12 years ago and thats why i shed that one. since i'm not an everyday rider, it got to the point where every nice day i had off (which sometimes is few and far between in the midwest) i spent more time trying to get it running then enjoying the ride/ and always in the back of my mind was "how to get home if/when it breaks on the road?"

 

[posplayr]

Sorry, I dont think there is any bullet proof solution, but with a replacement regulator/stator this probably will have a significantly improved margin of safety. Of course the proper grounding needs t o happen because the motor cycle configuration is much more suseptable to problems.

For cost reasons motorcyles use this simple permanent magnet generator configuration which is really only "good" for fixed speeds/fixed loads with no way to control the output power as speeds/loads change. With no way to control the generator power, you have to simply short (shunt) the excess power to ground and produce heat in both stator and regulator.

Unless you want to adapt some type of new electro magnetic exciter with brushes you have to work around the problem. The brushless PM is very simple mechanically. But extra care needs to be taken to make sure that the limitations do not bite you.


http://www.thegsresources.com/_forum/showthread.php?t=117925&page=2

More later after I have read some more links but got to get to bed now.

Posplayr

 

[SPARKSS]

Glad to have you aboard Posplayr. The design of this typical (of small engine) charging system is indeed a continuously sliding compromise with the exact problem areas you've described. I'd opt for a controlled field alternator if room could be found NOT in such a disasterous running environment. One idea (none of this is a quick idea) would be the brushless controlled field design (rotating claw pole) such as the Delco 30si etc. Another idea I've been mulling over (which might be more practical) would be a stator core (used with the existing or similar rotating PM) which would saturate and limit it's output magnetically as engine rpm increased. Certainly for best reliability and engine performance, any increase in rotating mass or offset drive could be detrimental. No engineer here.....just a working wrench and electronics tech (not of microscopic technology either).

 

[posplayr]

Hi Sparkss

Hi Sparkss

Thanks for the welcome. As I mentioned I am trained in this stuff (30 years ago) but it is not my particular area of expertise (if I had one).
I am concerned enough about both the stator and the rectifier/regulator to swap out to the Electrosport models.

lThough I don't have the motorcycle schematic yet (manuals still on order) I did discuss the schematic from the tutorial with two experienced electronics type at my work. The basic comment was that the brushless 3 phase with the simple shunt linear regulator was just "cheap crap". It was basically shocking if this is how Suzuki delivered bikes for many years.

The main suggestion short of trying to synchronously control the stator flux (to reduce output power) was to install a chopping series DCC regulator that was rated for the current and voltage. This would relieve both the stator and rectifier stresses at high RPM. I'm hoping (maybe wishful thinking) that the Electrosport model stator was rewound for reduced high RPM output and the regulator is a Series unit. At the very least I hope Electrosport did not use a SCR/Zener shunt regulator (geezz this is crap) in the R&R.

I have a digital scope with a current clamp probe which will allow me to upload screens to my laptop. I'm going to measure the original working units (current voltage of stator,R&R, headlamp, and charging currents etc) I have and compare the performance to the new Electrosport models. I will post the results of the assessment after I get all parts and can perform the tests. Give me till after Xmas.

Pos

 

[SqDancerLynn1]

If you are conserned remount it to get more air or hook up a computer fan to the regulator

 

[posplayr]

DaveWallen

DaveWallen

I just saw your post and I was considering the same today. It might help if the two units are closely matched so they share current. Then you have basically more power handeling capacity. Otherwise it might be that only one carries the shunt current and the other waits in reserve. Not the best solution but possibly better than no backup which is what a single regulator is. This also does nothing to reduce the stress on the stator when it is cranking mega amps at 10K RPM.

A better solution is to have the series regulator then if it fails (hopefully open) then the generator power goes no where. With the shunt regulator, if the shunt dies (open for example), then there is no place for the generator power to go but cook the battery and fry the electronics. If it shorts it is worse.

Even if the series regulator shorts it is no worse then the best case shunt. And more than likely the series will go open or have no output so it is hard to argue that there is any situation where the series regulator is worse than this shunt approach. 99% of the time it will be better.

Bottom line is that it will help about a 1/4 of the potential problems but ther are better approaches (I think).

Posplayr

 

[Guest]

You might want to hunt up the project by martin bakalorz (bakalorz@gmail.com) for a more robustly designed R&R. It's on this site...