Any Input on this PMA rotor for 10si or12 si

[ncgyver]

http://www.windbluepower.com/Permanent_Magnet_Alternator_Rotor_Fits_Delco_10SI_p/pma-rot.htm

[mobile_bob]

depends on what you plan to use the alternator for?

if you plan on an engine driven alternator?  perhaps it will be ok if you can regulate the output sufficiently for your needs

if on the other hand you plan on using the alternator for a windgen, i would suggest you pass and go check on far more
efficient and useful designs from "fieldlines.com"

bob g

[ncgyver]

Yeah, It would be engine driven Battery Charger.

[rl71459]

At the risk of sounding stupid... What is the benefit of a PM alternator other than self excitation.

Not looking for a "White Paper".... just a brief summary.

Rob

[DanG]

It's "White Paper" or nothing...  here is a 20 minute thumbnail of your question...

An automotive style alternator is designed to be a small parasitic load off the motor both mechanically & electrically - in a vehicle its' peak 1/3 to 3/4 horsepower 'hidden' load is forgettable. They work at 'high' RPMs via a dependable mechanical attachment, and consume some small electric power as a simple way to decouple the alternator when the systems needs are satisfied (the excitation regulation scheme).

Automotive alternators are not really designed to be long-lived on purpose, 12,000 driven miles in a year at 50mph average is 240 operating hours - or just under 3% usage per year, or 40~ minutes a day. They are installed in an area with cool(er) airflow and minimum vibration, and drive only a known load - and suffer from mass-production cost cutting to get 100,000 units sold for a nickle less, a sealed disposable unit. The premium for modified internal parts is steep since there is no mass-market for them. To get a better quality alt, look at the 24V over-the-road truck alternators, http://www.prestolite.com/pgs_products/alt_search.php but be prepared to choke on the suggested prices!

The PM alternator has no electrical parasitic load and usually operates at a lower RPM level so matching one into a purpose-built charger-source is maybe easier. The PM alt is dedicated to where the costs of running the engine figures in, and can be made more efficient input/output wise. If building a PM unit the bearings and cooling can be tailored to the application...

Ran out of time - someone else may finish the post (or not)

[mobile_bob]

fwiw,

for an engine driven alternator, the pm converted gm alternator is a miserable choice in almost everyway except from maybe
first cost of the alternator itself, however factoring in the cost of a pm rotor and you are getting close to the cost of a "real"
alternator that can do some series work and do it at much higher efficiency than the pm converted gm alternator ever thought to doing.

the field coil in a hd alternator might consume somewhere around 50 watts or less, for the cost of those watts you get very easy control
over the units ability to charge.

there are two ways to control the output of a pm alternator (within reason) the first and cheapest is to vary the rpm  of the engine, however
this calls for you either baby sitting the charging and reducing the rpm as needed to keep the charging in check, or you can run the engine
at a fixed rpm and use a charge controller much like a solar controller to vary the output power via pulse width modulation or some other scheme.

the use of such a controller means additional cost, but you don't have to baby sit the charging either.

pm alternators are fine for windpower, (at least those that are able to effectively charge in reasonable winds) where the loss of 50 watts
to power a wound field would be seen by some as an unexcuseable loss.

depending on what you have in mind, what voltage you want to charge, whether or not it will see significant run times and not just a backup
duty used once in a blue moon, you probably will be better off considering the following...

buy a 110-555jho alternator (prestolite- leece neville), and a sterling 3 step regulator,  the combination can be had for less than 300 bucks if you shop around. this setup will run circles around a pm converted delco  or any other small frame alternator. it will be more efficient, longer lived and capable of much higher output. you won't have to babysit the charging of your batteries either.

this suggestion is for 12 volts nominal, however the same parts can be repurposed to do 24volt charging too, however you will need to take a look at the white paper to learn how that is done.

the only way i would use a pm converted delco is if someone gave it to me, and i only planned on intermittent use for charging a dead battery in one of my cars/trucks. i would never buy one of them, nor would i allow a friend to do so.

ymmv
bob g

[RogerAS]

Bob,

Excellent post. I agree with every single point you raised.

When one uses a PM rotor the excess power generated toward the end of change cycle must be dumped off into a load of some kind, and to me that's a bigger waste than the power consumed in a wound rotor. Unless one can use that excess end of cycle power for something useful it's a waste of fuel too.

R

[rl71459]

Thanks

It all makes sense to me now.

Rob

[ncgyver]

10-4 thanks for the info. I really need to get this going so I'm going to go with Bob's recommended equipment. Anything else I should consider ?
What is the best source to purchase the 110-555jho  alternator from? I an have 8 hp B&S waiting to be hooked up/

[SteveU.]

Hi All
I am glad you succinctly clarified this Mobile Bob.
I have been sitting on my tongue not to blab in. I was in the automotive generator/alternator/starter/battery business for 16 years. The Delco 10SI was an excellent auto production unit superior to all of it's 60's-70's contemporaries when limited to ~63 amps ~790 watts. The 12SI was better with a wider two lamination stack stator wider heavier rotor claw pieces and better cooling strategy. Good for ~75 amps - 940 watts. Limitation on any of these is conversion efficiency X the ability to get rid of waste heats. Why the truck, industrial and marine units were always large case, heavier, larger bearing slower RPM units to keep the operating temps down, the RPM wear factor down for 2X-5X the longevity.
Sure. Sure. I hot-rodded small case units especially the Delco's to get them to up to and past 100 amps. All about taking a $45-65 quality rebuild ($20 profit) of a $120-150 when new unit ($30 profit) and pimping it up to over $100+ with $60 profit. Really, really does helps out the profit line. Chrome High Amp? Sure. They overheated the worst if actually used at full output. I even painted one pink - don't ask. Best longevity I found was a 10SI JD tractor unit with cabs and an AC package if they were painted flat black with the 12SI vacuum fan and open ventilated front case, 15SI bearing enhancements and the Ag swing arm brush holder pkg. OE manufacturers knew all of this  - why for small case units they have mostly evolved into dual internal fan open cases designs for thier small cased units. Chrysler had it right but could never pull off the build quaility. Why they finally just went Nippon Denso for OE.  The most power/fuel efficiency conscious of the OE's if there was any advantage to PM rotors would have changed over just like they did with many of the starters. They have NOT.

Bottom line the 10/12SI PM rotors conversion units are to transfer money from your pocket into someone else's. Crank up the output watts past 1000 for over 45 minutes continuous, they will overheat. Keep this up for a couple of hours and you will let the magic smoke out stator windings.

Don't want to go with a truck unit? You should if you can - they ARE more conversion efficient. Then go with a reman of a factory  larger case 15/17SI Delco, a larger case 70-90 Amp 70's Ford light truck/automotive #7072-74

My money stays in my pocket anymore
Washington State Steve Unruh