PMA's (permanent magnet alternators) up to 50% more efficiency :)

[jtanguay]

A little background information first. A PMA uses permanent magnets in the rotor rather than using generated voltage to energize the field. Benefits of this method are higher efficiency due to strong permanent magnets available, higher output due to not having to energize the field, and longer lasting due to the absence of brushes. PMA's are becoming really popular for wind and hydro power generation for the do-it-yourselfer. I say, why not use them in cars??? Check the picture below for what the rotor looks in comparison to the stock 'claw'.

vs.

I can predict that the rotating inertia will be greatly reduced simply by switching to the PMA rotor...

So now we get to the point of this thread... I haven't heard of anyone cracking the 'code' on how to get these things to properly regulate their output to what our cars need. 13-14V @ 90 amps requires a pretty complicated DC-to-DC converter. I'm learning a bit about toroidal transformers, and I think they could help regulate the current. The idea would be to create a 'mock' alternator with no moving parts, and regulate the inductance within the toroid using the stock voltage regulator (or a pwm/555 timer circuit... and a mosfet). The only problem is that toroidal transformers are quite expensive.

Now why would anyone want this on their car? How's about 2-3 mpg sound? That extra charging juice could also go towards an electric heating to warm the car up faster. VW added a much larger alternator AND battery to the glow plug heater equipped cars...

Maybe if we put our heads together we can find a way to make this work, and work right. I'd like to use the KISS (keep it simple stupid) approach 

[gldgti]

interesting idea. unfortunately i'm mech eng, not electrickery, haha.

from what aspect of the permanent magnet option makes it difficult to regulate the voltage? (oh, i think i know - the fact you cant reduce the magnetic field strenth at will, right? haha....)

the definatly non KISS method would be to do with a CVT belt drive.... but forget i even said that.

more thought required.

[macka]

PM motors can be tricked easily to vary output. The easiest is load resistance, you could use a circuit to control the output. Using a CVT would be interesting, considering you keep a fairly constant rpm until it maxes out at the top end.

[jtanguay]

PM motors can be tricked easily to vary output. The easiest is load resistance, you could use a circuit to control the output. Using a CVT would be interesting, considering you keep a fairly constant rpm until it maxes out at the top end.

hmmm sort of like 'dumping' excess voltage/current? wouldn't that increase the resistance on the engine though? i was also thinking that a pulsed charge controller (using capacitors to smooth it out) could increase the efficiency even more and use a transformer to get a bedini style circuit going and use some free electricity 

now i've been pondering a few other ideas... such as electric supercharger and the poor mans hybrid (yep!) by using many capacitors. the idea is that the caps are charged during normal driving, and using a controller, during acceleration the alternator can be switched to a motor to help the engine accelerate, and then switch back when the voltage gets too low. (that would be quite complex... 50amp relays might be needed, and large caps too)

for the supercharger, a complex circuit could be made to turn an alternator into a variable frequency motor. a PWM circuit could be used to spin an alternator at around 16,000 rpm and not use too much juice. once the alternator is spinning above a few thousand rpm, energizing only one phase could bring it up to its maximum speed. best part about this, is that when its shut off, theres no pulley load on the engine, and it can be mounted much easier. however, i think the stator would need to be re-wound in a different pattern to be effective in this type of setup. (three phases separate from eachother, not inter-linked)

i've also thought about using power MOSFETS to regulate the a/c juice, and then send it to a rectifier pack. the problems that i forsee, is trying to get the high amp output regulated at 13-14 volts... i'm thinking a mosfet like this one would be cheap enough to use one on each phase... any inputs?

[rabbitman]

The hybrid part would be neat but I wonder how the vee belt would like it

[macka]

the mosfets controlling a charge into caps seems to combine the best of 2 worlds without putting excess load on.

[maxfax]

Yep it's about time this was discussed..      Although ya'all blew away my limited electronics knoledge now..  I'd just been looking at simple ole "cut-outs"..   With a cap in the line to even things out..    But then again my old IDI isn;t quite as suseptable to spikes and drops in voltage as something mroe modern.......

[jtanguay]

The hybrid part would be neat but I wonder how the vee belt would like it

i'd say the v belt could support 1-2hp or just a tad bit more. nothing spectacular, but imagine the engine free revving without the alternator? that is essentially what would be achieved

[jtanguay]

Check out the Bedini circuit below. a lot of people have had great success with charging non rechargeable batteries, and using very little energy to do so. not sure how this could be worked into the system yet, but i'm thinking... check out youtube for bedini circuit or bedini charger for more info.

[burnt_servo]

isn't this really not much different than what was used before alternators ? fixed magnet generators .

wouldn't it be easier to  go back in time and see how the various companies back then used to control  voltage output , rather than try to reinvent the wheel ?

[jtanguay]

isn't this really not much different than what was used before alternators ? fixed magnet generators .

wouldn't it be easier to  go back in time and see how the various companies back then used to control  voltage output , rather than try to reinvent the wheel ?

hmmm you might be on to something! thanks for the input

edit: after some reading, the generator's use electro magnets as well to generate the magnetic field??? hmmm...

[Turbinepowered]

Just out of sheer curiosity, what's the efficiency of a current-tech alternator? Isn't it something like 60-75%? 

I know we have AC motors that are 85% efficient, induction drive and all that.

I'm just not seeing a "50% increase" in efficiency with something that's going to add parasitic equipment to the whole system, and especially not from a starting point of already 60-75% efficient.

[maxfax]

isn't this really not much different than what was used before alternators ? fixed magnet generators .

wouldn't it be easier to  go back in time and see how the various companies back then used to control  voltage output , rather than try to reinvent the wheel ?

hmmm you might be on to something! thanks for the input

edit: after some reading, the generator's use electro magnets as well to generate the magnetic field??? hmmm...

This is tha angle I have been loking at...   Basically about the same thing as used on small engines too.. I *think" the magnetic fields in generators had something to do with regulating current..  Energized when the load was higher, etc..   That would however be counter productive..   

Now if we go to REALLY old stuff the generator was a simple fixed magnet generator with what was called the "cut out"..  IF voltage got above the setting (say as in a high rpm situation) the circut would be broken between the generator and everything else..   IF the voltage dropped too low (high loads, low rpm) then cut out would complete the circuit again...  THe down fall was that if you were in the high load/low rpm situation the generator would still not be making much power and you;d be heavily relying on the battery..  Most of these coudl at least maintain battery voltage at slightly above idle... Alot of the old service manuals (we're talking back in the 20's) would say to adjust the cut out to the driver's habits..

Alternator efficiency is around 50% - 65% pending on the load..   A 50% gain may be pushing it a tad, however with a PMA if a good way of regulating could be found the effeciency doesn'y change all that much with load if I understand correctly...  ANd since load wouldn't decrease efficiency one could opt to electrically operate other things (such as a water pump or power steering) and remove that load from the engine..   OR as mentioned electrically heat the engine for faster warm ups...

[Turbinepowered]

Okay, now I found what I was getting that 60-75% figure from. A Bosch press release.

According to their release, part load efficiency is about 55%, with one of their newest line of big commercial alternators hitting about 70% efficiency.

Some of the wikipedia article's sources give a range from 55-62% efficiency, with small PMA systems already in existence being about 65-68% efficient.

[maxfax]

The 55% - 65% would be the older Delco Remy alts that GM used over 20 years ago..  I'm sure (or would at least hope) that something a bit more modern woudl be a bit more efficient..  A PMA in place of a regular alternator most likely would not be beneficial enough to warrant the hassle..

I've switched to one of the wind blue PMA's attached to the water wheel on the spill way of my pond..   It spins a fairly constant 300 RPM..  (Faster after heavy rains and snow melt)..  I have the pond lighting and pavilion lights all powered from it, even with the meager water flow it powers everythign nicely, no battery needed except in a drought...

The 2 electro magnet alts I tired (modified for this purpose) could barely keep themselves energized and I ultimately needed to have a battery connected in the system..  It did manage to keep the battery charged most of the time...

On the car, I'd like some electric heating to help switch to WVO faster..  A standard alternator of say 130 amps would be a hideous draw running such a large load, and probably inadequate still..