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What are the leading causes of stator failure?

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I've gone through more stators than I've like to admit in 16,000 miles. Failure seems to be at random and to varying degrees. Is it pure co-inkydink or is something wrong? I change my oil on a regular basis (Full Syn), run a 55W headlight (No higher wattage than OEM headlight on bright) and have done the free power mod.

What do you think? Both in my canse and in general...

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I don't think load has anything to do with it as the stator always runs at full power. Either your ancillaries take the power or the R/R will ground it, it's all the same to the stator - or is it?

If you run more than the stator has power to feed you'll just start taking from the battery and flatten it, the stator doesn't care.

Why some die and others don't is a mystery.

What I'm struggling to get my head around is power transfer. If the load resistance is equal to the stators coil resistance then you will get 50% voltage drop and the power will be dissipated equally - so that would mean approx 100 Watts of heat in the coil. If the R/R goes lower than equal resistance then it could mean 75% or more power getting dropped over the stator, which would mean more heat in the windings.

Best solution might be to have the power being used on the bike (headlight etc) as that will dump less heat in the coil.

When out riding my R/R is mostly cold, this could be due to the lower revs I do so the stator isn't generator so much power. Maybe people with high failure do higher sustained revs??

That would put more heat in the oil and in the windings...

Just my thoughts on this...:smirk::bonk:

Edited by DrzDick
typos...

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Yeh, I was responding to the OP.:smirk:

I think every time this topic comes up we get a little further to understanding it so I'm hoping this time could be the one lol.

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If the OP has had multiple stator failures in 16k miles doesn't that point to a problem with his specific bike? I have 15k miles with no failures and I think most here have not had multiple failures in that amount of miles...

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The rest of your post DrzDick seems to contradict itself. You have stated the stator is putting out full load at all times, to a powered device, the battery, or to ground.. And I agree.

So since that is a constant (above RPM x ) what the stator "sees" in load, heat generated by load is also a constant I think.

ah, I've only just seen the rest of your reply so sorry for not addressing it in my previous response.

The stator puts out full power not load, load is not down to the stator.

Full power meaning all the power it can give, this increases as the revs do.

The R/R attempts to make this more or less constant above a certain revs by shorting any voltage peaks to chassis (0 volts). This is not limiting the power in the stator but is protecting the bike electrics from it.

So the higher the revs the more power will be dumped by the R/R and the more will be dissipated in the stator. The stator resistance if fixed and will be higher that the resistance of the R/R when it is activated so in worst case you could be dumping most of the 200 Watts of power as heat in the stators windings.

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Not sure I follow this...

The electricity (power) is used by the R/R and remainder of the circuit. The resistance/load seen by the stator does not change, other than by RPM. The R/R should isolate it from the circuit. The power produced by the stator then "never" changes. It should not care where it goes as it always goes.... So regardless, the stator temp should be only it's "running" temp, which will vary by ambient conditions (engine and oil temp).

IMHO the failures are simply that. It may be quality, it may be environmental. It has been alluded to by some on this forum that it may also be oil related. But no one has studied it in any detail as Erik notes.

Given the total number of DRZ's out there and the total number of failures seen, it strikes me as a common problem but not that widespread. If a given bike has repetitive failures there is something else going on as well.

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Not sure I follow this...

The electricity (power) is used by the R/R and remainder of the circuit.

Yes, but the R/R effectively shorts the circuit so the power is both being created by, and used by the stator in the form of heat.

The resistance/load seen by the stator does not change, other than by RPM.

Nope, the resistance seen changes all the time. Resistance is Load seen by the stator and will change often.

The R/R should isolate it from the circuit.

Nope, The rectifier turns the stators AC output to half wave or full wave rectified DC. The Regulator is like a watch dog. If the voltage peaks too high it clamps it by shorting to 0volts. The R/R is not a transformer so will not isolate.

The power produced by the stator then "never" changes.

Nope, the frequency and voltage peak increases with revs so the total power generated is increasing with revs.

It should not care where it goes as it always goes.... So regardless, the stator temp should be only it's "running" temp, which will vary by ambient conditions (engine and oil temp).

It does not care where is goes but if it gets shorted to 0volts by the Regulator then the power actually get dissipated through the stator more than in the regulator. This power will add heat to the stator, probably lots of it hence why the stator is oil cooled.

Given the total number of DRZ's out there and the total number of failures seen, it strikes me as a common problem but not that widespread. If a given bike has repetitive failures there is something else going on as well.

Agreed.:smirk:

Edited by DrzDick

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ive said this before but every bike ive personally had in my presence for a stator failure has one thing in common. oil that was obviously way over due for a change.

not once have i said,"wow,this guy keeps up on oil changes". its always nasty.

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Yeh, I've got to say that after thinking about this for sometime... I don't think we realise how much wasted power gets dumped into the stators own coil. I wouldn't be surprised if an E, S or SM is dumping 150 watts of electrical energy into the stator windings which is being dissipated as heat.

If the oil is already spent, and hot it could burn on to the stator and act as an insulator.

A question to PO - what did the stators you replaced look like?

Burnt or just broken?

Were they Suzuki original new parts, after market or used?

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ive said this before but every bike ive personally had in my presence for a stator failure has one thing in common. oil that was obviously way over due for a change.

not once have i said,"wow,this guy keeps up on oil changes". its always nasty.

That is good to know!!! Thanks. :smirk:

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Yeh, I've got to say that after thinking about this for sometime... I don't think we realise how much wasted power gets dumped into the stators own coil. I wouldn't be surprised if an E, S or SM is dumping 150 watts of electrical energy into the stator windings which is being dissipated as heat...

So does this mean it would actually be better on the stator if we consumed this extra power elsewhere? For example: would running heated gear while at highway speeds actually better on the stator since the extra power isn't getting dumped into the stator windings?

Thanks,

WGW

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Not being an electrical engineer I'm out of my element here. Yes I also question what happens when the RR regulates power. I know the power is not dissipated as heat in the RR. (The RR gets hot from the inefficiency of the rectifier diodes passing power on down the line) The question in my head is does the stator produce the power then have to dissipate it as heat when the RR regulates? Or is the power just not produced (or severely reduced) when the RR is shunting the coils?

For excited field alternators, I understand how the regulation works - magnet strength is reduced and the power is not produced. For permanent magnet types, it's more vague. I understand that the RR shorts the windings to themselves but I don't understand the physics of that.

I have also read that there are 2 kinds of permanent magnet alternator regulators-those that go open and those that shunt. But for some reason the "open" style are not commonly used.

Since we are concerned with heat, I wonder how the following would compare for temperature?

- a normally connected fully functional normal load condition.

- All 3 stator output wires open circuit.

- All 3 stator wires shorted together.

There must be some electrical engineers out there with power generation knowledge.

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So does this mean it would actually be better on the stator if we consumed this extra power elsewhere?

I would say so.

As long as you are not pulling so much power that the battery isn't charging then the more you can use up around the bike the better in my opinion.

I'm an electronics engineer BTW so I'm not just regurgitating something I've read on another forum or anything. I generally do understand how the thing works but I must confess to not being a motorcycle R/R expert as I have never make one, up to now..., but could if I had too:ride:

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I know the DRZ uses old technology SCR type R/R and I wonder if a newer style MOSFET R/R would help the stator life at all? I don't know much about the differences between these technologies but I know the newer style is more efficient and cooler running - maybe it would be easier on the stator?

Just not a lot of room in the stock R/R location so it may be tougher to find a MOSFET R/R that physically fits.

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Outstanding .. Have you have a chance to look at the system diagram for this bike? :lol:

Im not an EE, nor do i play one on TV.. So only know what I know... Can always learn more :smirk:

Whoa, check the attitude please...

We're just trying to get to the bottom of a problem and not trying to prove anything. Unless that is genuine praise, I doubt it...:lol:

I was impressed by your previous post, about seeking advice from a specialist as I am keen to learn also.

I will happily admit if I'm wrong and I have previous looked at the diagram, as I've already said, I am familiar with electronics so it does make sense to me.:bonk:

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I know the DRZ uses old technology SCR type R/R and I wonder if a newer style MOSFET R/R would help the stator life at all? I don't know much about the differences between these technologies but I know the newer style is more efficient and cooler running - maybe it would be easier on the stator?

I don't think so, being more efficient would mean it drops less power over itself - that mean slightly less heat at the R/R and slightly more on the stator windings.

It does mean the MOSFET R/R should last longer though as heat is one of the main factors which effects semi-conductor life.

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I interpreted E. Marquez comment as directed at himself. (self deprecating and humorous)

If I remember my college days correctly there is a difference between EE and EL. Power generation and transmission in EE, right? About the only thing I remember is 3 phase "delta" vs "Y" wound configurations.

I tend to agree with DrzDick in regards to using most of the power generated. In my observation, permanent magnet alternators tend to be fairly closely matched in output to the load. This could be just economics but could also be limited ability to regulate down the output

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I know the DRZ uses old technology SCR type R/R and I wonder if a newer style MOSFET R/R would help the stator life at all? I don't know much about the differences between these technologies but I know the newer style is more efficient and cooler running - maybe it would be easier on the stator?

I've been reading up on the MOSFET R/R and it just might be kinder on the stator and also provide more power to your equipment!

It all depends how the in-built controller is operating the MOSFET's but potentially it can just chop the voltage peak rather than shorting out the whole pulse once it gets over the cut off point. If that is the case then it will be much better for the stator.

Might be something for the OP to try if stator burn out is a problem.

Edited by DrzDick

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