What would burn up a lawn mower stator? I have a Briggs inteck, 21 horse, one lunger, 5 amp regulated system on a Hustler zero turn. apparently quit charging over the winter. Went to start it for the fourth mowing, and the battery was dead. Found some specs on the 'net that showed a problem with the stator. pulled off the flywheel and 7 of the 8 coils are toast. I would put the battery on a Battery Tender for a couple of days at the first of every month to keep it charged. Can't find a shorted wire or anything not normal. Thanks.
- Thread starter Little Ed
- Start date
Billy Shafer
Well-known Member
How clean is it. Grass clogging the cooling air. Can cause them to overheat.
steve_in_mo
Well-known Member
A bad voltage regulator/rectifier depending on the application could burn up the stator.
Replace both, then test your wiring harness for shorts, and put her back to work.
Replace both, then test your wiring harness for shorts, and put her back to work.
MarkB_MI
Well-known Member
- Location
- Motown USA
I'd sure replace the regulator along with the stator.
Most small engines use a "shunting" regulator/rectifier. When the instantaneous voltage of a phase exceeds the regulated voltage, that phase is shorted out. A consequence of this is that the LESS current demand on the alternator, the MORE heat the stator generates. But the clutch and charging load of a ZTR should be more than enough load to limit the shunting to a minimum. My guess is the regulator failed some time ago and eventually the stator burned out.
Most small engines use a "shunting" regulator/rectifier. When the instantaneous voltage of a phase exceeds the regulated voltage, that phase is shorted out. A consequence of this is that the LESS current demand on the alternator, the MORE heat the stator generates. But the clutch and charging load of a ZTR should be more than enough load to limit the shunting to a minimum. My guess is the regulator failed some time ago and eventually the stator burned out.
Correct me if I am wrong, but . . Most of the Briggs charging systems I am aware of use permanent magnets in the flywheel. Stator windings can only get burnt up when an outside power source gets to them. Not enough power with the stator-magnet system to hurt itself. I have not kept up with the newest stuff so maybe what you have is different. On the older machines - burnt windings meant battery current getting to where it does not belong.
MarkB_MI
Well-known Member
- Location
- Motown USA
>...burnt windings meant battery current getting to where it does not belong.
And the only thing between the battery and stator is the regulator/rectifier.
And the only thing between the battery and stator is the regulator/rectifier.
regulator gone bad can cause it,but seldom ever seen that what idid see a lot of was jumping the unit from a running vehicle or mowing your lawn with the motor not running at full rpms both of these will make the stator/ alternator look like a molten puddle of plastic. sounds like your unit has not been working correct for some time if you been putting charger on it all time,thats always sign of no charge. also have seen mice nest chew wires so it can not operate correctly under the cowling. when you were charging did you unhook battery of just clip it on, some chargers will be to much. ran small engine shop for 11 years seen about every thing tried. also you need to double check the clutch have seen them short out but not very often.
I agree with Mark and I agree an outside power source (such as the battery) can burn up stator windings.
The stator has its output wires connected to the regulator/rectifier and it in turn is connected to the battery so it can receive a charge. The flywheels rotating magnet passing by the stator windings induces an AC voltage which the rectifier changes into pulsing DC which charges the battery. If sufficient energy and voltage, say from an outside energy source like the battery, got somehow ??? improperly connected to the stator windings, I sure agree it can possibly (under right circumstances) overcurrent and damage them.
At least that's how I've seen several brands configured, I cant guarantee its how the OP system is wired nor am I familiar with all the different brands and how their charging system operates.
Nice sparky chatting with yall, best wishes
John T
The stator has its output wires connected to the regulator/rectifier and it in turn is connected to the battery so it can receive a charge. The flywheels rotating magnet passing by the stator windings induces an AC voltage which the rectifier changes into pulsing DC which charges the battery. If sufficient energy and voltage, say from an outside energy source like the battery, got somehow ??? improperly connected to the stator windings, I sure agree it can possibly (under right circumstances) overcurrent and damage them.
At least that's how I've seen several brands configured, I cant guarantee its how the OP system is wired nor am I familiar with all the different brands and how their charging system operates.
Nice sparky chatting with yall, best wishes
John T
Just a guess but doesn't your mower have a plug-in master fuse rated at 15 amps? It seems that fuse should blow before the battery could burn up your stator behind the flywheel. Have you verified that the fuse is still the right size? I am wondering if a wiring problem developed and at some time, someone stuck in a larger then OEM fuse? The 5 amp charging system only maxes out at 14 volts alternating current. The regulator-diode assembly should blow before any stator wires melt. Again, just a guess.
Steve@Advance
Well-known Member
I'm trying to see how even a bad rectifier would let battery backfeed to the stator.
If 12v were backfed through the rectifier, it would simply apply positive voltage to one or both sides of the stator with no place for it to go to ground unless the stator was shorted internally.
I'm thinking maybe the stator is capable of generating enough heat, combined with engine heat, to burn the insulation. As in a shorted to ground stator wire, a bad rectifier/regulator, bad battery, overloaded electrical system...
Interesting, just the other day I was working on a B&S V twin something, The battery was low after starting it several times. It had an amp meter on the dash, and I noticed with it running at speed, it would charge heavy for a few seconds, then return to center, then charge again, then stop, repeat. Evidently there is some type thermal protection that cycles it. As the battery came up, it dropped back and charged steady.
So, if I found a burned out stator, I would for sure replace the regulator/rectifier, load test the battery and charge it if good, clean out the cooling fins.
I was looking at a B&B service page, there are many types and amperage charging systems, so there is no one size fits all answer!
If 12v were backfed through the rectifier, it would simply apply positive voltage to one or both sides of the stator with no place for it to go to ground unless the stator was shorted internally.
I'm thinking maybe the stator is capable of generating enough heat, combined with engine heat, to burn the insulation. As in a shorted to ground stator wire, a bad rectifier/regulator, bad battery, overloaded electrical system...
Interesting, just the other day I was working on a B&S V twin something, The battery was low after starting it several times. It had an amp meter on the dash, and I noticed with it running at speed, it would charge heavy for a few seconds, then return to center, then charge again, then stop, repeat. Evidently there is some type thermal protection that cycles it. As the battery came up, it dropped back and charged steady.
So, if I found a burned out stator, I would for sure replace the regulator/rectifier, load test the battery and charge it if good, clean out the cooling fins.
I was looking at a B&B service page, there are many types and amperage charging systems, so there is no one size fits all answer!
The flywheel magnet and stator charging systems on many small engine systems put out very low charging current at voltage not much higher then the 12.6 volt battery. HOWEVER the batteries are indeed big enough if one got its 12 volts incorrectly across the stators winding there could be enough current and resulting heat given sufficient time to fry the stator grrrrrrrrrrrr. To do so IF THERE ARE NO OTHER SHORTS OR WIRING ISSUES I, like the fine gents below, suspect a rectifier/regulator problem. However a short in the wiring that caused battery voltage to get across the stator, now that could fry one also.
Id first inspect the wiring for shorts then replace the stator and rectifier/regulator if needed. That's not all that hard or expensive once the flywheel is removed. Been there done that n got the T shirt myself lol
John T
Id first inspect the wiring for shorts then replace the stator and rectifier/regulator if needed. That's not all that hard or expensive once the flywheel is removed. Been there done that n got the T shirt myself lol
John T
Yo Steve, Indeed its tough to figure out from here just what happened or what caused it. Regardless a wiring short or a major defect in the rectifier assembly might somehow ???? cause it. I have no data as to the max voltage and current the magnet and stator system can generate (as I'm sure you know it depends on RPM and magnetic field strength) and how much heat it can dissipate into any maximum or short circuit load, but its hard to see it could be enough to destroy itself?? but what do I know sitting here ???????????
As always a pleasure sparky chatting with you, take care
John T
As always a pleasure sparky chatting with you, take care
John T
MarkB_MI
Well-known Member
- Location
- Motown USA
The schematic shows the regulator hard-wired to the battery. So a shorted diode in the regulator could certainly cause current to flow through the stator when the engine isn't running, resulting in the stator overheating.
In motorcycles, regulators and stators tend to fail together. A bad stator can cause a regulator failure and vice versa.
In motorcycles, regulators and stators tend to fail together. A bad stator can cause a regulator failure and vice versa.
MarkB_MI
Well-known Member
- Location
- Motown USA
> I have no data as to the max voltage and current the magnet and stator system can generate (as I'm sure you know it depends on RPM and magnetic field strength) and how much heat it can dissipate into any maximum or short circuit load, but its hard to see it could be enough to destroy itself??
John, the shunt-type regulators commonly used in small engines generate maximum stator current with no load. Which is one reason you always want to have a battery installed.
Some of the newer motorcycles with higher charging system capacities are going to series-type regulators that limit the output current to regulate voltage rather than shunt excess current. For these regulators, the higher the load the greater the stator current. The downside is the series regulator must dissipate a lot of heat at typical load conditions.
FWIW, motorcycle stators often rely on engine oil for cooling, which gives you an idea how hot they might get.
John, the shunt-type regulators commonly used in small engines generate maximum stator current with no load. Which is one reason you always want to have a battery installed.
Some of the newer motorcycles with higher charging system capacities are going to series-type regulators that limit the output current to regulate voltage rather than shunt excess current. For these regulators, the higher the load the greater the stator current. The downside is the series regulator must dissipate a lot of heat at typical load conditions.
FWIW, motorcycle stators often rely on engine oil for cooling, which gives you an idea how hot they might get.
"John, the shunt-type regulators commonly used in small engines generate maximum stator current with no load. Which is one reason you always want to have a battery installed."
Thanks Mark, that makes sense. Absent any details or specs I just don't know if the rotating magnet and stator charging system, which is relatively low energy, even at maximum conditions (whatever and when ever that may be) can over current and overheat enough to fry itself ????? perhaps so if its NOT incorrectly getting across battery voltage due to a rectifier problem ??
Love sparky chating with yall
If it were me Id replace the stator AND THE RECTIFIER and insure there's no wiring shorts WELL DUH lol
John T
Thanks Mark, that makes sense. Absent any details or specs I just don't know if the rotating magnet and stator charging system, which is relatively low energy, even at maximum conditions (whatever and when ever that may be) can over current and overheat enough to fry itself ????? perhaps so if its NOT incorrectly getting across battery voltage due to a rectifier problem ??
Love sparky chating with yall
If it were me Id replace the stator AND THE RECTIFIER and insure there's no wiring shorts WELL DUH lol
John T
Wow,that's a lot of information. The rectifier must be in the voltage regulator. No separate diode in the harness. and the fuse is correct and good. Things are all pretty clean. Stator and VR should be here tomorrow. not a difficult set up, just don't like throwing on parts and hoping for the best. Thanks to all that read and responded!
MarkB_MI
Well-known Member
- Location
- Motown USA
> The rectifier must be in the voltage regulator.
Correct. It's technically a "regulator/rectifier". The stator output is two-phase AC, which is rectified to DC in the regulator.
Correct. It's technically a "regulator/rectifier". The stator output is two-phase AC, which is rectified to DC in the regulator.
I agree with Mark, I've seen a ton of those small rectangular block devices with spade terminals, some call them a Regulator some call them Rectifier used on small engine charging systems. Indeed there are diodes inside that rectify the stators AC output to charge the DC battery. Anytime I have a flywheel off I clean up the magnet and hopefully with a new stator and Rectifier/Regulator if there are no shorts and a good battery what can go wrong ????????? hmmmmmm lol
Piece of cake right??
John T
Piece of cake right??
John T
If you are having to charge the battery every month, Probably you needed a battery a long while ago.
My experience is that usually the charging system burns up trying to satisfly an no-good battery or an electric clutch that is drawing way too many amps because it has a shorted winding.
My experience is that usually the charging system burns up trying to satisfly an no-good battery or an electric clutch that is drawing way too many amps because it has a shorted winding.
Hi.... on the off chance that you detach the 3 wire plug from the recti-frier , run the cutter and the electrical switch doesn't pop then the recti-frier, or the wiring to it are suspect.
The Kohler manual has directions for checking the opposition of the stator to decide whether it has a short.
The way that you are creating power implies that the circuit is finished however doesn't preclude a short.
https://www.7pcb.com/
This post was edited by JethTran on 08/06/2021 at 11:19 am.
The Kohler manual has directions for checking the opposition of the stator to decide whether it has a short.
The way that you are creating power implies that the circuit is finished however doesn't preclude a short.
https://www.7pcb.com/
This post was edited by JethTran on 08/06/2021 at 11:19 am.
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