Standard alternator or stator

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slociviccoupe

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I have had this on my mind for a while now. But what is considered better or more acceptable. A standard alternator or a permenant magnet generator (3 phase stator, magnetic rotor and voltage regulator)?
Pros to an alternator is internal or external regulator, can be turned on and off manually. Voltage regulator will detect when battery low and charge automatically.

Cons. Belt driven, takes power to make power (field current)

Permenant magnet generator.
Pros. Simple, belt or direct drive, no parts to wear out.

Cons. Cant turn it off, any waste power made gets turned into heat at the regulator.

Figure if sized correctly it should output the power needed. Can bolt the mag cup to the crank pulley and bracket to hold the stator. No belts needed.

Seing what your thoughts are.
Seems all the smaller engines in powersports still using stators. Either packaging or weight or both.
 

Toobuilder

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"Better" is defined by requirements. My airplane requires 25 -30 amps just to stay airborne. What does yours?
 

slociviccoupe

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"Better" is defined by requirements. My airplane requires 25 -30 amps just to stay airborne. What does yours?
Havent built anything yet for myself. Working on firewall forward subaru.
But if 25-30a to stay airborn and if making correct 45a output then not far off from using the energy made and not wasting it as heat in the regulator. That is for permenant magnet setup. A stsndard alternator will either vary field current or just turn off till battery voltage drops and turn back on and start charging again.
 

Dan Thomas

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The alternator is the way to go. Easily controlled and efficient. A pm generator represents a constant max load on the engine, and dissipating 40 or 50 amps of unneeded energy makes a lot of heat that you burned extra fuel to create. If you don't dissipate it the voltage will run away and fry anything connected to the system. A tiny pm generator is fine for an amp or two to run a radio, but for anything serious you want an alternator.
 

TiPi

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The PM alternator does not have to be short-circuited to be regulated. A decent PWM regulator and a bridge rectifier will remove the load from the alternator when not required. The open circuit voltage of the B&S 16A PM alternator is about 30V AC. Many regulators can handle more than that. It does require some extra circuitry/components to be able to run without a battery, this depends on the type of regulator.
This is probably the simplest option (for single-phase alternator): KEY WEST PS030 REGULATOR / RECTIFIER | Aircraft Spruce
 

Dana

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The Key West regulator is fine for the "lighting coils" on many 2-stroke engines, but I wouldn't want it on anything much larger. Also they need some load to keep the voltage stable, I had a couple of big 10W resistors with a heat sink, the strobe wasn't enough.

There are lots of good reasons why all cars today have field alternators and not PM generators. Small engines use PM generators because it's easy to slap a couple of magnets onto the flywheel to handle both ignition and the lighting coil.
 

slociviccoupe

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Just inquiring but doesnt the new shindigen regulators use mosfets and pwm and instead sinking to resistors it hooks one phsse to another to cancel out the load on the stator. At least thats what i got from reading.
Im fine with one of the denso mini slternators but if i can mount an aluminum mag cup to crank pulley with a stator in it and no belts that would be ideal.

The only other reason ive thought or considered is because the john deer, kubota and others are just this. A stator, permenant magnets and a voltage regulator.
And lot of aircraft guys use them.
 

Dan Thomas

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One of the drawbacks of PM alternators is that they might not produce enough power at idle, depending on the load. You see it on machines that use them: the lights dim at idle. Modern radios need a stable voltage and many will drop offline when the voltage falls below 11 volts or so. Some of them need to reboot when the power comes back up.

The old generators were replaced partly for reasons like that. In old airplanes the generator didn't start producing power until the engine RPM was at 1200 or more. At idle the battery was supplying everything, and at night you could suffer considerably if you didn't get off the ground real quick. The other thing with generators was their weight for the power produced, and the fact that all the produced power went through brushes and commutator, both significant wear items. The carmakers went to alternators in the mid-'60s and the aircraft manufacturers followed almost immediately, a rare occurrence.
 

slociviccoupe

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Prety sure just going to drop the idea of pm and just mount denso alternator. Was good thought at first. Already have enough things sgainst me using subaru so better not make my charging system another.
That said though the wire thatvturns thecregulator on usually switched ignition source i would put on a fuse and switch so i can manually turn it on and off.
Mainly in case there were an issue i could switch the alternator off and run till battery voltage dropped and everything quit.
 

Daleandee

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There has been some really great information shared here by guys that know much more than I do. But I'll give you my thoughts on using a Dynamo and then a few caveats.

Many experimental airplanes use stators (Dynamo) for electrical power. The Corvair, Jabiru, and many VW conversions come to mind.

My airplane is electrically dependent so I need a reliable source of power to the ignitions. The Dynamo we use on the Corvair is used on John Deere lawn equipment. It is 20 amp and has permanent magnets. The only parts that move and wear are the front a rear bearings. We also use the same regulator as the lawn equipment. These units are very robust. Mark Langford describes them here:


20 amps in my airplane is enough to run everything as needed including the transponder and wig/wag lights. Admittedly at idle it doesn't charge much but bumping the throttle up to about 1200 brings it back into the charge range. That's only necessary if I'm idling on the ground with everything on.

Caveats would be that they need a good regulator. Cheap ones won't save you money. The one that it uses on the lawn tractor is made in Japan and it works very well. Also, keep in mind the wiring of your airplane if it is truly electrically dependent. For the sake of safety I have a B&C over voltage package on mine that will shut down the regulator if the voltage gets too high. It controls a relay that's wired into one of the A/C lines from the dynamo. My reason for this is that I seen a Jabiru that melted the regulator down the firewall because the disconnect was in the 12 volt line from the regulator. So the power from the dynamo was able to fry the regulator even thought it was disconnected from the system.

I like the dynamo system but it has its drawbacks as others have pointed out. Mine has worked very well for eight years so far ...
 

slociviccoupe

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There has been some really great information shared here by guys that know much more than I do. But I'll give you my thoughts on using a Dynamo and then a few caveats.

Many experimental airplanes use stators (Dynamo) for electrical power. The Corvair, Jabiru, and many VW conversions come to mind.

My airplane is electrically dependent so I need a reliable source of power to the ignitions. The Dynamo we use on the Corvair is used on John Deere lawn equipment. It is 20 amp and has permanent magnets. The only parts that move and wear are the front a rear bearings. We also use the same regulator as the lawn equipment. These units are very robust. Mark Langford describes them here:


20 amps in my airplane is enough to run everything as needed including the transponder and wig/wag lights. Admittedly at idle it doesn't charge much but bumping the throttle up to about 1200 brings it back into the charge range. That's only necessary if I'm idling on the ground with everything on.

Caveats would be that they need a good regulator. Cheap ones won't save you money. The one that it uses on the lawn tractor is made in Japan and it works very well. Also, keep in mind the wiring of your airplane if it is truly electrically dependent. For the sake of safety I have a B&C over voltage package on mine that will shut down the regulator if the voltage gets too high. It controls a relay that's wired into one of the A/C lines from the dynamo. My reason for this is that I seen a Jabiru that melted the regulator down the firewall because the disconnect was in the 12 volt line from the regulator. So the power from the dynamo was able to fry the regulator even thought it was disconnected from the system.

I like the dynamo system but it has its drawbacks as others have pointed out. Mine has worked very well for eight years so far ...
I certainly appreciate the reply and your input.
My thoughts on a dynamo/stator on the subaru conversion was to mount an aluminum mag cup to the crank pulley and mount stator on a mount infront of it. Was going to use the shendigen voltage regulator. The stator was sourced from a yamaha jet ski and is 3 phase 45a unit. In the ski it charges battery, runs fuel pump and ignition and bildge pump continuously.

Like your plane i will be electrically dependent for the fuel pump, ignition, efi, and all the other acessories.
 

Daleandee

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Like your plane i will be electrically dependent for the fuel pump, ignition, efi, and all the other acessories.
A little off topic but I mentioned the concern I have for being certain that I always have ignition power. I only use Odyssey batteries and have had excellent service with them. They have a three year warranty and usually when the warranty is out I put a new one in and put the old one in my Z-turn, motorcycle, etc. Odyssey batteries charge at 14.4-15.0 and recommended charge voltage is 14.7. My dynamo is right there at 14.7 or 14.8 depending on which voltage readout I believe. I tried to pay attention to the requirements of all the pieces and assemble them so that they would play well together. I started with a "Z" wiring diagram designed for my plane by William Wynne (Fly Corvair) & Bob Nuckolls (AeroElectric).

I wired my ignitions so that if the alternator shuts down there is no interruption of ignition power. I don't have dual batteries so I'm taking the odds that I won't lose the dynamo and the battery at the same time. If that should happen it will be time to execute an emergency landing or "fly it all the way into the crash" depending on my options.
 

rv7charlie

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Any links to the Yamaha pt nos, dimensions,etc for that unit? 45A is a useful size. BTW, a friend has run a Harley alt between the flywheel and reduction on a rotary, so it's certainly a reasonable idea.

Charlie
 

pfarber

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You're gonna save some weight with an alternator, and the proper under drive pulley will get you enough 'idle current' once you know what you need. Typically 2000RPMs is the magic number.

An alternator is a very high reliability device.

I use generators on my antique trucks and they are a PITA. Gotta magnitize them, then keep the commutator clean, then brushes wear/springs lose tension, undercutting mica is always fun. Or mount alternator. Run 1 wire to to the bus, enjoy.
 

slociviccoupe

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So very smart friend of mine who builds 3 phase brushless motor controllers mentioned to me thatca permanent magnet alternator is nothing more than a brushless motor. Most of us already knew that. But he also said instead of using a voltage regulator that uses a diode bridge to rectify current and then mosfets and resistors that make heat and waste, to use an igbt and a microcontroller. The igbt is exactly what is in a 3 phase brushless controller and prety much you would be using the regen feature of the controller as charging your battery and getting 14? Some volts dc out of the controller from the stator. He also mentioned one phase can be connected to another and as it is making current it is adding it to another coil on other side of stator and it cancels the load on the rotor and allows it to freespin with no load.

He said honda mopeds have been doing this for a bit now and the stator has even replaced the starter motor and is used as sort of a hybrid assist.

Its very interesting because now knowing you can essentially turn ofc the stator and use it to cancel eachother out to make no load it seems very viable to mount a rotor with magnets to the crank pulley and run a stator. No brushes, bearings or belts to worry about. Just spinning magnets and then your controller.
 

pfarber

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But he also said instead of using a voltage regulator that uses a diode bridge to rectify current and then mosfets and resistors that make heat and waste, to use an igbt and a microcontroller
Why not just get a one wire alt? Why mess with a stand alone regulator?
 
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