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Back when dirt was new and I didn't know any better I used to mess around with Harley Davidsons. Changing the stator on a shovelhead Harley was a major undertaking and it wasn't unheard of to buy a new defective stator. I built a test fixture using a 1/2 horsepower 3600 RPM 110 volt induction motor. I was surprised to find there was a small but measurable load and a slight increase in temperature of the stator even though the stator wasn't connected to anything. That's when I learned about magnetic hysteresis. With a regulator connected to the stator but no load on the regulator there is a very significant load and a lot of heat in the regulator and the stator. The bottom line is this a 1/2 horse induction motor had no trouble speeding the rotor up to 3600 RPM no matter what the load on the charging system. Horsepower loss in the charging system is pretty much a non-issue.heat on the other hand is probably a matter of concern judging from all the fried stators I've seen.

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19 hours ago, joblock said:

I built a test fixture using a 1/2 horsepower 3600 RPM

 

I'm surprised the HD parts survived having that much power and RPM applied.  They are not meant for that.

 

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On 10/9/2020 at 12:25 PM, SwampNut said:

 

Since I'm not sure whether you don't know how each work, or don't know why one method is preferable to the other, here's a short version of a long story...  Regular shunt-type regulators just dump excess power to ground.  The excess energy is wasted as heat.  A series regulator interrupts the output of the alternator when it is not needed, so there's less heat and less power wasted.  On a large bike the power makes no difference.  The theoretical advantage for series is that they should last longer since they don't get hot.  I disagree.

 

There are multiple issues to consider. Here is a quick shot at a list.

 

A shunt regulator does get very hot , as the power it absorbs can be quite high and increases with RPM. High temperatures do lead to accelerated failure rates in solid state electronics. So putting lower load lighting on your bike actually increases the heat load in the RR unit.

 

Power loss; a permanent magnet alternator with a shunt regulator will always be at maximum load for a given RPM. As the voltage from the stator is directly proportional to RPM, higher revs will mean higher frag on the crankshaft. Given that the spec is around 300 Watts, the HP loss should be less than 1hp though this might very a lot over the RPM range.

Stator current; as the shunt RR shorts out the coils to limit voltage, the current through the stator coils will be quite high. I suspect that this is the primary reason for the stator to fail, as the unit should otherwise last decades like any other brushless induction motor or generator.

 

Stator connector; it is quite common to see the stator connections on bikes with shunt RR's to be damaged by heat. The high current is too much for the simple faston type connections and they tend to degrade badly over time.

 

Series regulators; More complicated electronics, as they need to synchronously switch a mosfet switching device. Likely  will have more power available at idle if designed well.

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Hi all, 

 

I’ve read through this and I’m not understanding why a series regulator would be better than a mosfet here?   My understanding is that Mosfets run cooler than original, I guess the series runs cooler again?

 

I swapped my R/R for a shindengen FH020AA mosfet and my carbie stator for the electro sport fi stator.  The idea being that the extra power will help run accessories I’m adding to the bike without overloading the stator.  Am I now to understand that the mosfet will run hot like the oem unit just not quite as hot?

 

i also have a VFR750FL that has had reg rec issues in the past and I’m aiming to get both bikes into a decent place with the charging circuit.

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The original and mosfet both consume all the unneeded current from the stator, basically it's a regulated short circuit to keep the voltage steady.  All the extra current being produced by the stator that isn't being consumed by stuff on the bike is consumed by the regulator which creates heat.  The mosfet does a better job and might run cooler.

 

A series regulator creates a controlled open circuit instead of short circuit.  It 'disconnects' the stator so that there is no extra power being created.

 

Imagine that you had no throttle control so the engine is always running at full power.  The only way to keep the bike at cruise speed is to hold the brakes, the excess energy from the engine is being consumed by the brakes, that's a shunt type regulator.  The series regulator is a throttle.  You added a higher output stator so any time that your accessories aren't on there's more power being consumed by the regulator.  In the stator/engine analogy you installed a more powerful engine pushing against the brakes.  Turning on your extra accessories would be like putting on luggage, it'll eat up some engine power so you can ease up on the brakes.

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21 hours ago, superhawk996 said:

The original and mosfet both consume all the unneeded current from the stator, basically it's a regulated short circuit to keep the voltage steady.  All the extra current being produced by the stator that isn't being consumed by stuff on the bike is consumed by the regulator which creates heat.  The mosfet does a better job and might run cooler.

 

A series regulator creates a controlled open circuit instead of short circuit.  It 'disconnects' the stator so that there is no extra power being created.

 

Imagine that you had no throttle control so the engine is always running at full power.  The only way to keep the bike at cruise speed is to hold the brakes, the excess energy from the engine is being consumed by the brakes, that's a shunt type regulator.  The series regulator is a throttle.  You added a higher output stator so any time that your accessories aren't on there's more power being consumed by the regulator.  In the stator/engine analogy you installed a more powerful engine pushing against the brakes.  Turning on your extra accessories would be like putting on luggage, it'll eat up some engine power so you can ease up on the brakes.

Professor Hawk. 😀  Not a jab, that was a good epexegesis. 

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On 10/21/2020 at 7:44 AM, superhawk996 said:

I'd never seen/heard that word, and I do it a lot.

Me too.  Who knew?

Too bad I'll never get the pronunciation right.

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