MOSFET convert...

[ArrrGeee]

Thank you Jason, you are correct.
I was just about to comment on that...

[Rikugun]

You can't shut the magnet down but you can intermittently ground one or more stator coils thereby reducing output and heat generated.

[ArrrGeee]

no, I don't think I buy that, the magnets are creating power in
the stator. whether you do something with it or not.

shorting it to ground I suspect is where the heat is getting created.
typically if you short a wire out, it turns red hot and melts the insulation.
but with a simple light load on it, you'll find that the wire is maybe warm to the touch.

in my unqualified opinion, the reason the mosfet transistor is popular now is because
it is better able to fool the stator into thinking there is a slight load and allows it to run cooler.
someone who is more versed in the tech could probably give the details on the duty cycle
and how it behaves.


-Ron

[Rick G]

Where is leather when you need him?

[ArrrGeee]

sure, but lets look at it logically.
your typical alternator uses an electromagnet to create power in the stator,
alternators are what modern automobiles and many motorcycles use.
it's much easier to control your power output by energizing the magnet
as needed. That is my understanding of how current is regulated.
All alternators are AC and need a rectifier to convert to dc.

so now with many motorcycles including the vision, due to cost consideration,
Permanent magnets are used instead of an electromagnet.

The permanent magnets are always lighting up the stator, the regulator
either shunts to ground or goes into the charging circuit
and the current is rectified to before going back to the battery.
Now obviously this is just a simplified explanation
but this is what makes me wonder. would it be smarter to just go open circuit
so instead of shunting current to a ground, one or more legs of the stator circuit
become open, thereby ( in theory ) reducing the heat because there is no load.

so then if this is indeed how the switching transistor is able to to go open circuit
on one or more of the legs, then that might explain the cooler running and
how several bike manufacturers have ( potentially ) solved the stator problem.

if you hunt around on many honda / kawasaki / suzuki forums you'll find that they are having  stator/reg/rec failures as often as the vision does. the mosfet regulators seem to be the cure...
it's on my todo list

ymmv

-Ron

[kwells]

an open circuit will do nothing with it's power that is how one would turn 'off' a charging system. It would not matter what the configuration. Our permanent magnet systems will do nothing with the potential if they are unhooked from the system. There is no 'backup' of power if there is nowhere for it to go.

[ArrrGeee]

exactly, so, no load, no heat, no fried stator.
all praise to the technology gods  ;-)

[Rikugun]

no, I don't think I buy that, the magnets are creating power in the stator. whether you do something with it or not

Not true, when the stator is grounded it's no longer producing power otherwise stators that fail by shorting to ground would continue to function. The scenario I described was used way back when on some Japanese models that utilized current limiters. They were 3 phase full wave systems that had conventional 6 diode rectifiers. Connected in between the 3 sets of 2 rectifier diodes were 3 thyristors (linked to ground) and a zener diode linked to bat + which comprised the "limiter". It sensed and dealt with over charging by systematically shutting down stator legs by grounding them. There may have been 3 different resistors employed as well to incrementally stagger the stator's shutdown. It's been a while and I don't recall all the details.

Automotive and older motorcycle used AC alternators with an excitable DC powered field. AC output was determined by field strength controlled by a mechanical regulator. Whatever AC was made went through a conventional full bridge rectifier to charge the battery. In bikes, although an efficient system, the inherent complexity (both manufacture and diagnosis) and cost to produce was it's demise.

I think when you refer to heat generated by grounding current is the typical scenario described when talking about conventional R/R like the OEM Vision unit and others - maybe even the MOSFET? I never quite understood this explanation or merits of the system but the permanent magnet/stator produces full output all the time relative to RPM and regardless of need. The excess is then "shunted" to ground by the regulating part of the R/R where all the electrons zip around inside the frame forever and ever or until exhaustion and they fall asleep or die.  ???  :D  This system apparently generates lots of heat in both the stator and R/R. The latter was apparently addressed by MOSFET circuitry but not necessarily the former.

[Re-Vision]

True. When current flows and heat is dissipated, power is created. P=IE. The only way to stop current flow with coils moving through an magnetic field is to open the circuit. Even if you ground both sides of a coil, current will flow when magnetic and electrical fields move through one another.     BDC

[Rikugun]

Hmmm, interesting. So would you say there is less, more, or the same heat/current flow in a grounded stator vs. and ungrounded stator?  And what is the path of the current flow?

[Re-Vision]

I would say that there is approximately the same heat/current flow in a grounded stator leg as its all going to ground somewhere anyway. If you are grounding all outputs of stator I would think that a measurement of AC output at different RPM's would help to measure actual Voltages and calculate power losses. Whatever Voltage is generated by a stator winding will be dissipated as heat across any resistance the current meets in its flow to ground. The Vision system has an ungrounded neutral so current should flow into any two legs of the stator while flowing out one leg and so on ad infinitum. Its where the heat is dissipated that causes problems, better the RR unit and electrical components than the engine case or stator windings and wires. Shorting out one or more windings of the stator to ground is not what causes the stator to fail, its the heat build-up that causes the circuit to overheat and eventually open up.   BDC

[ArrrGeee]

Amen, Thank you Bobby.

a broken system is still a broken system. if it's a shorted stator it's broken.
what I found suggested somewhere else on the web is that the new style
regulator operates by cycling from shunt to open circut to control the voltage
and produce less heat. hence the term duty cycle. so if that is a given then
potentially, vision stator problems are a thing of the past..
now that_ is a bombshell, guess we'll have to lose the flame logo that I'm so fond of  :D

[Rikugun]

Bobby, thanks for the response and just to clarify I'm not suggesting grounding a stator causes it to fail. Overheating can open the circuit (more typically) but also can ground it when the insulative material burns/melts away allowing contact wrap to wrap and to the stator core. Obviosly it's cooked by then so my analogy of decresaed output is a mute point. Having said that I doubt the output (intact but grounded) is similar to an un-grounded stator or at least relative to what the R/R realizes. Speaking of heat, my understanding is the Vision system is prone to high stator and engine case temps - even with good connections. You seem to suggest the heat is isolated to the R/R but later site heat build up in the stator as a factor to it's demise? Maybe I'm misunderstand your comments.

ArrrGeee, that's a very interesting notion that of the hybrid R/R, can you provide a link? I wonder if any motorcycle used the open stator approach to voltage regualtion. It seems odd that the shunted R/R type became and remains the dominant in use yet opening the stator is apparently (in theory) the way to go. A hybrid system seems even more dubious. If one approach is vastly more effective and results in less heat why fool around with the other even in a partial capacity. Perhaps there's more to it than vague theory!?  ;D  :D

[ArrrGeee]

Rikki, I've been referring to the FET (mosfet) type regulator.
now obviously, I've been using some generalizations in my descriptions
but I was trying to convey the general concepts.

there are reasons for both style of alternators, and I believe that
all of the bike manufacturers would prefer a standard alternator type if there
was enough room or it didn't make the engine too wide.
ie you can't run brushes in an oil bath.

regulating a permanant magnet system has a different set of challenges
that apparently has eluded all of the bike manufacturers for some time.
a big one for us is the age of the bike and the quality of the connectors.

 so, again here's to hoping the technology gods have fixed the nagging stator problem once and for all

 {{ymmv}}

-Ron


http://www.youtube.com/watch?feature=player_embedded&v=YazISsTVGec

[Re-Vision]

Rikugan,

You can't shut the magnet down but you can intermittently ground one or more stator coils thereby reducing output and heat generated.

Normal output circuitry will always have rectifiers presenting a load to AC output Voltages (Which limits current flow and in turn, power dissipation.) plus regulated DC loads. Whenever a ground is introduced upstream of the rectifiers it no doubt will cause the Voltage to decrease because load resistance will move toward zero while current flow will rise toward infinity. Therein lies the problem area, coils and stator wires are not designed to handle this extreme power dissipation (heat). Below are arbitrary numbers showing how the stator system will have to dissipate heat while trying to maintain Output Voltage when the load resistance is reduced to zero.

Output Voltage  (E)           Load Resistance (R)              Current (I)           Power (IxE) Watts

100 VAC                          10 Ohms                             10 Amps               1000 Watts
100 VAC                          5 Ohms                               20 Amps               2000 Watts
100 VAC                          2.5 Ohms                            50 Amps               5000 Watts
100 VAC                          0 Ohms                               Infinite Amps        Weakest spot burns up and opens circuit  

Admittedly, Output Voltage will likely decrease beyond ability of coils to maintain normal Voltages. Even so,Ohms Law says that current will increase exponentially until something gives. Our system gives up when wiring overheats and opens. If we had heavier duty wires it would just have a heat build-up and that's not good either. Voila, the constant rectifier load plus whatever the regulator presents is within the design parameters of our system.

BDC

[supervision]

  Goggle, SSR-vs-FH0122AA  Best explanation of the series reg.

[Rikugun]

Ron, Well that is interesting. This is the first I've heard the MOSFET functioned by cycling between shunt and "opening" the stator circuit. Admittedly, I haven't done much research on them in general. I knew they charge at low RPM and run cooler so when the time came for replacement I used one. I've read claims (including on this site) that they're still a shunt style and the stators were therefore still vulnerable to heat damage so this is the first regarding the enhanced functionality. I thought the YouTube link would be a technical dissertation on the matter but was disappointed  >:(  Is that yours or just a random bike with the MOSFET mod?

Thanks for the explanation Bobby. I especially liked "Admittedly, Output Voltage will likely decrease beyond ability of coils to maintain normal Voltages." That must be where theory runs into practical reality!?  :D

[Re-Vision]

Rikugan,

Thanks for the explanation Bobby. I especially liked "Admittedly, Output Voltage will likely decrease beyond ability of coils to maintain normal Voltages." That must be where theory runs into practical reality!?  :D

I don't know for sure how well the circuitry works, reckoned I'd throw that out there and see if anyone would correct me. Used to work at a transformer company and engineers would tell me how little I knew, the engineer who owned the company said he thought that he knew transformers until he talked with a physicist.    BDC

[ArrrGeee]

  Goggle, SSR-vs-FH0122AA  Best explanation of the series reg.

"Your search - SSR-vs-FH0122AA - did not match any documents.  "


have a link ?

[ArrrGeee]

no, the video was just an example of another manufacturer having charging problems
and going with a mosfet convert, it's an epidemic evidently.

Sorry Rikki, Bobby has got me beat in the rocket science dept, I was just paraphrasing
what I had read elsewhere on the net.  The mosfet style regulator uses a fast switching transistor
that duty cycles between shunt and ground, possibly many times per second.
this reduces the load and also the heat created.

here is a brief ( possibly better) description from another site:


<quote>
What is the difference between a thyristor and a MOSFET based R/R?

The switches in the Regulator part are either type, but they both do the same thing... The rapidly turn on and off, shortcircuiting power to ground to keep voltage constant... That's called "Shunting", and almost every type of bike R/R used now is made this way...

Every time you short circuit something, it creates heat, just from the short circuit... That's the same for both types... But, the difference is in how you switch!

On a thyristor based R/R the most heat isn't from the shortcircuit, it's from the switching... A thyristor is basically a diode with a separate leg, acting as a switch... But the switch has a delay... The thyristor relies on the current flowing through it, to keep it open...

Basically the switch opens the door a crack, and then waits for the current to crash into the door, slamming it open... Closing it is similar... You slowly, slowly push the door closed enough until the current looses power and cant hold the door open, slamming it shut...

As a result, the thyristor is horribly inexact and inefficient... It takes time to switch, and it creates huge amounts of heat while doing it...

The MOSFET is a bit more intelligent... It doesn't rely on the current for opening the door, and it doesn't try to close it slowly... Instead the switch is really a switch... Switching it on means it starts to conduct fast, and switching it off means it stops almost as fast... That creates a lot less heat, and makes it more exact... A lot more exact.
</quote>



hopefully that helps.

-Ron