Second stator lost voltage output

[Sidewindo]

Hello Everyone

This is my first post as a long time reader. New to me low KM sidewinder first season started with two tows on trail. First was a busted chaincase next was stator failure. This season first ride was awesome. High voltage charge low coolant temps. Cable scratchers on skis help consistency. Second ride voltage is not picking up forcing me to turn around. I tested stator and all same symptoms as last year. Before I replace the second stator (RM stator 2 year warranty) is there something that can cause these to prematurely fail. Is this my luck to have two faulty stators in a row. I turn off the kill switch and tether cord between rides. No tune on this sled. What could possibly cause this. I do know some vehicles have coding for a choice of batteries either AGM or lead acid. I am waiting on an appointment with my local dealer to check for any problems. Are there any features in the YSDT that can help. Is there a common break in the wire harness to pay attention to.

 

[sideshowBob]

IMO...
I would never run anything but a Yamaha OEM stator. I don't know what would cause a stator to fail under normal conditions.

 

[Confused]

IMO...
I would never run anything but a Yamaha OEM stator. I don't know what would cause a stator to fail under normal conditions.

I'll 2nd this. I've never had an aftermarket stator last in anything.

 

[earthling]

Power draw is what causes failure. And poor quality. You can use a 1000w generator to power 100w bulb but you cannot put a 1000w load bank on a 100w generator. Other factors include heat which typically comes from generating power but their could be external heat sources. It could be a faulty ground on the other side of the voltage regulator keeping the stator at max load but... (shrug) who knows. I would have a really close look at the windings when you pull the stator. Inconsistent damage (burnt windings in one spot) probably says something about the uniformity of the windings, quality of coatings (presuming coatings), etc..

 

[jonlafon1]

I lost a stator on my 2017. No idea what caused failure. It just failed. I replaced it with a Yamaha one and never had another issue. I think I was around 5-6k for mileage when mine went out. Mine started acting funny the night before. It started kinda hard a time or two. I parked it for the night at the cabin next morning all that would happen was the sled would crank crank but not start. We tested resistance on it and bingo was his namo.

 

[turbogts22]

I don't really buy the whole "power draw causes failures". Whatever power the stator puts out in watts has to either be consumed by the load of the sleds electrical system or by the regulator in the form of heat. If you reduce the sleds power demands the regulator just shunts the freed up power to ground and generates more heat. If it didn't do this the stators voltage would creep up and start blowing bulbs, ect.

https://en.wikipedia.org/wiki/Linear_regulator

 

[earthling]

I don't really buy the whole "power draw causes failures". Whatever power the stator puts out in watts has to either be consumed by the load of the sleds electrical system or by the regulator in the form of heat. If you reduce the sleds power demands the regulator just shunts the freed up power to ground and generates more heat. If it didn't do this the stators voltage would creep up and start blowing bulbs, ect.

https://en.wikipedia.org/wiki/Linear_regulator

My understanding is that in practical terms and with windings in perfect condition you are right, its not draw so to speak but as you reach the rated capacity of the alternator (stator/generator/whatever) and as the windings age, load and heat matter. It is also not a matter of generating power, as generation (capacity) is fixed by engine speed and the rectification of AC into DC and regulation of DC. On the surplus of power production side you are completely right, excess gets shunted into heat. But we are not talking about excess production, we are talking about excess of load. All generators (alternators, whatever) are rated at a duty cycle and capacity. Pragmatically speaking you should never be near that because you have a battery to soak up excess demand but. excessive load comes in a lot of forms (a short to ground, running at capacity for over the rated duty cycle, a dead battery, etc). Of course poor quality, design, manufacturing defects or excessive environmental exposure can also cause problems. Completely misleading nonsense.. do not read the crossed out malarky.

Something was killing the first round of stators, there is massive evidence of that. The stator went through two revisions as I understand it while NONE of the other parameters have changed. The housing, gasket, rotator, mounting, engine, rpm, no environmental factors and no mechanical driving factors have changed. It wasn't a manufacturing defect because that wouldn't take two revisions to fix and would have been part of the upfront design specification. So what changed? What most likely changed is the capacity and or duty cycle rating (which is really a capacity and manufacturing thing). If it was the rectifier/regulator then that would have been changed, not the stator assembly.

Always willing to be wrong, and I could be, but it makes sense at least to me.

 

[turbogts22]

Hmmm, interesting. My take on it is that the rated output of the stator at any given RPM is always being consumed, either by the load or by the regulator. If you load the stator beyond its capacity the voltage will sag. If you don't load it enough either through actual load or the shunting of the regulator, the voltage will go up. Taking away load such as turning off heaters, ect only transfers the load to the regulator which converts it to heat. Very inefficient but it's simple and low cost which is why it's so commonly used.

 

[earthling]

Hmmm, interesting. My take on it is that the rated output of the stator at any given RPM is always being consumed, either by the load or by the regulator. If you load the stator beyond its capacity the voltage will sag. If you don't load it enough either through actual load or the shunting of the regulator, the voltage will go up. Taking away load such as turning off heaters, ect only transfers the load to the regulator which converts it to heat. Very inefficient but it's simple and low cost which is why it's so commonly used.

I wasn't going to get into the regulator but reflecting on my original post I realized that something didn't feel right, I was stuck thinking about the role of your linear regulator and after I wrote the above and hit save I realized that sometime during my scrumptious serving of apple pie that in trying to explain how heat matters I was very wrong about the cause which set off a misguided diatribe as to why. So I was (completely) wrong in my explanation to the extent that it was misleading. Misleading or mis explained is wrong so I was wrong. (he says in a monty python voice).

Staring over and fully caffeinated again.

First, there is no excess power generated by the alternator. I kept thinking regulator in the sense that if there was overvoltage then yes a regulator would perform the shunting function described and that would be perfectly right but then I realized that just isn't how its done. On chew number 2 of the pie I realized.. this can't be right. Off to find my old textbook, quick read... yup, I was wrong. The job of the regulator is to turn the alternator on and off, effectively creating a control loop by way of simply measuring available voltage and switching the alternator off when voltage exceeds nominal (14.5 or whatever) and turning it back on again when it falls below the threshold. It does this through control (excitation) of rotor windings using DC current. When you close (or activate) the circuit the alternator is engaged by way of DC current which is induced into the rotor and moves the field across the stator windings. This happens quickly. Those are the basics. The duty cycle (the ratio of on to off) is important because anytime you pass current through the system you generate heat. The more you excite the rotor the more often the alternator is generating voltage, the more heat you generate. So its not draw directly, as current isn't 'drawn' _through the stator_ its a byproduct of having to run the alternator more often (more duty cycle) in order to keep the voltage from sagging that induces heat and the only time you have to do that is if you have more current being consumed by whatever you are supplying voltage to. So the more correct and direct relationship is that more load (more lights, more heaters, more whatever) consumes more power which creates a sag in voltage which in turn causes the alternator to run more often. There.. that's a cleaner explanation.

Because it is on/off (very fast) or even if it is moderated more elegantly by microchanges in current these days (I only know 2o year old theory) , the alternator generates electricity (AC) but of increasing frequency. The more RPM the less the duty cycle (run the alternator less) because you have more opportunities (through the speed of rotation) to generate voltage. The lower the RPM the greater the duty cycle (the more you have to run the alternator). The job of the rectifier is to turn this AC back into DC and its the resulting DC voltage that the regulator uses in the loop to decide whether or not the alternator (stator) needs to be excited (or not). To complicate matters, the alternator has no excitation at rest when the vehicle is off so the battery voltage has to be in the ballpark to get the whole thing going. If the battery is in poor condition the regulator runs the alternator more. The role of the alternator relative to the battery is that only a portion of the alternator output is set aside for charging, otherwise your 'running' power is coming primarily from the alternator and spikes in load are backed up by the battery. If the battery voltage falls (or really system voltage because it is one bus) falls below nominal then the alternator must supply more voltage by being on more often. Conversely if your battery had a really high voltage the alternator would not engage until the regulator (which sees the load side) senses the voltage dropping below its threshold.

Now I feel better, of course I could be way more wrong

The relationship between load, duty cycle, and heat is real. Heat kills electronics, it weakens coatings, it ages insulators faster, etc..

Schooled! Does not apply to our Snowmobiles. Thanks for the education @turbogts22

 

[Simplespeed]

Something killing the first round of stators ? Massive evidence of that ? Does this mean there is good odds my low mileage 2017 may experience this problem??? To have a stator fail bites, to have 2 stators fail… it tells me there is another issue here causing it … Now if its the manufacturer of it thats the problem … then that really bites as we all rely on machine parts that are built and designed to work correctly as intended… Great write up Earthling…..

 

[turbogts22]

Something killing the first round of stators ? Massive evidence of that ? Does this mean there is good odds my low mileage 2017 may experience this problem??? To have a stator fail bites, to have 2 stators fail… it tells me there is another issue here causing it … Now if its the manufacturer of it thats the problem … then that really bites as we all rely on machine parts that are built and designed to work correctly as intended… Great write up Earthling…..

Your description is 100% correct... if we were discussing my Arctic Cat T660 Turbo. That sled uses a Suzuki car engine and alternator and works as described. The Yamaha engines and virtually every other snowmobile engine uses a permanent magnet alternator. The output of those cannot be regulated since the magnetic field of the magnets is, well "permanent". The only way to reduce "output" is to slow down the spinning magnets.

I can still remember working on older 60's - early 70's sleds when I was young. Most didn't even use a regulator. They simply matched the load to the max output of the stator which kept the peek voltage in check. When hand warmers came out they had to increase the output of the stators and utilize a regulator for over voltage protection since the load was no longer a constant. Whenever the heaters were switched off the regulator kept the voltage shunted. When the regulators died the lights on the sled would get REALLY bright at full speed, till they started blowing out.

I could be completely wrong here too, anything is possible.

 

[1nc 2000]

Put OEM stator in it. The aftermarket stators don't last. If you continue to use non yamaha stator you will change lots of them.

 

[earthling]

Something killing the first round of stators ? Massive evidence of that ? Does this mean there is good odds my low mileage 2017 may experience this problem??? To have a stator fail bites, to have 2 stators fail… it tells me there is another issue here causing it … Now if its the manufacturer of it thats the problem … then that really bites as we all rely on machine parts that are built and designed to work correctly as intended… Great write up Earthling…..

I probably overstated it with 'massive' but the changes to the rotor have been addressed in more recent machines (updated parts). The original stators and the 'massive' number of failures (to the point that it is a typical failure) seems to be pre-2010 (probably sooner) but it can happen to any machine. Our machines work in environments with giant temperature swings from frozen before you start to hot once you are going and thats going to be hard on any components.

 

[earthling]

Your description is 100% correct... if we were discussing my Arctic Cat T660 Turbo. That sled uses a Suzuki car engine and alternator and works as described. The Yamaha engines and virtually every other snowmobile engine uses a permanent magnet alternator. The output of those cannot be regulated since the magnetic field of the magnets is, well "permanent". The only way to reduce "output" is to slow down the spinning magnets.

I can still remember working on older 60's - early 70's sleds when I was young. Most didn't even use a regulator. They simply matched the load to the max output of the stator which kept the peek voltage in check. When hand warmers came out they had to increase the output of the stators and utilize a regulator for over voltage protection since the load was no longer a constant. Whenever the heaters were switched off the regulator kept the voltage shunted. When the regulators died the lights on the sled would get REALLY bright at full speed, till they started blowing out.

I could be completely wrong here too, anything is possible.

Ahhh, thanks for that. You are 100% correct. Thanks for being so tactful. Always trying to learn. The implication here is that with fixed capacity and only simple regulation then the battery must take up the slack. If you are overloading the system then you must be killing the battery. Interestingly, in those high draw situations the regulator is working less(?) although the entire circuit has to be rated for that continuous max load? Brutal but simple and it means that any failure in there (stator) means its only a matter of time before the battery is dead which explain the scenario where the sled starts but dies on the trail? Stator was bad. (those are implied questions, not statements)

 

[Turboflash]

Stators are not designed for 100% duty cycle meaning they are not designed to have to output at 100% continuous. Heat will kill it if that is the case.
I would definitely check (both visually and electrically via DVOM) carefully for a short to ground somewhere, especially up near fuse block area.