Source for PMG's? Seem to be all gone...

[RJ]

Is it me, or has the supply of 60hz PMG's vanished...


Tom doesn't seem to list them anymore. George... same story.

What's the scoop? Did they note live up to expectations?

Could be in the market for a smaller 3kw and larger 10kw unit....

As usual a google search brings up all sorts of vendors from china.

-Randy

[sailawayrb]

Perhaps priced out of the market by the Chinese?  I think the Chinese are holding the rare earth material closely so as to use it for manufacturing the associated products and thereby obtain a higher return on investment.  A very capitalistic play from a so called communist state...

Bob B.

[bschwartz]

I'd love to have one myself.

Due to an error somewhere along the line, I ended up with a 8k PMG generator head....... but it's 50hz.

[mobile_bob]

quality control became a serious issue with the pm heads,

the design of a pm head dictates that the magnetics be nearly perfect, and remain so over the life of the machine, under the full range of operating parameters with temperature being the biggie.

getting quality neo magnets that are certified to do the job became very difficult at the price point acceptable to the buying public. they got so expensive and the guarantee of quality so uncertain that it became to risky to continue bringing them in.

there were and are some other wannabee manufactures that assemble with neo's of questionable quality, questionable design and cooling capacity, that will sell you a pm head, some of them are just plain garbage and will not produce their rated power over the long haul.

with china tightening up on neo sales, and with all the electric car crap, all the quality neo stuff is likely not going to end up being used in a very niche market.

its buyer beware now.

i don't think this is likely to change anytime soon either, so we probably ought to consider the pm generators a thing of the past.

bob g

[Henry W]

I tested a 8Kw 1800-RPM PMG About 3 years ago and it failed miserably. It was supposed to be a 60-Hz unit but turned out to be a 50-Hz. Under  load it measured 220 volts @23 amps @ 50-Hz which is only 5060 watts. When I loaded it full output voltage droop went to 207 volts.

Not very good in my opinion.

Henry

[TimSR2]

I'm not surprised. PM alternators give up control over regulation to the magnets that they are built with. If the magnets decay, due to age, quality or overheat, they become an expensive door stop.  There is an extremely tight design process to make a successful fixed voltage pm alternator. They are also very intolerant of airborne contaminants.

They were/are considered the 'holy grail"  in wind power  applications because there is no field power requirement.  But the voltage is wild and varies upon rpm...  I'd rather design a controllable alternator with field control, and perhaps sacrifice the 50 watts  field power to have control over the output voltage.

On an engine set, the field power consumption is  inconsequential. There is just no advantage to PMA.  On a wind power setup, it makes more sense to go PMA, but still I think that with good design a proper electromagnetic field controlled alternator system could do better, and be easier to control. Perhaps a tiny PMA wind gen or solar panels , or a better controller would offset the field losses of a  wind system based  on a more controllable EM field system.

PMA's are more efficient, but don't we really want our voltage supply within a controllable range, if we are trying to charge batteries? 

[Henry W]

Now lets the Eagle Pitcher PMG Alternators.

I like them very much when rectified to 24 volt or 48 volts DC. They are efficent. No need to worry about 60 Hz. So voltage droop will not be a problem. These are not cheap run of the mill PMG's. I have three  Eagle Pitcher PMG's and They are very well built. I am planning to finish a system with an Eagle Pitcher in the future.  

Here is the link of the project   http://www.microcogen.info/index.php?topic=2800.0

Henry

[sailawayrb]

You make a very good point Tim.  I had forgotten that some folks actually use PMGs for AC applications.  I have always thought them only useful for efficient wild AC rectified DC applications.

Bob B.

[BruceM]

+1 TimSR, I'd rather have voltage control via excitation, at least for a ground mounted 60 Hz generator.

I think it was Ronmar who tested one of George B's top quality units, and found that efficiency wise, there was no gain for PMG (60Hz generation)  compared to an ST head.

It's value was a high reliability,  EMP proof, electronics free generator head. It did meet those goals quite admirably, and that's no small feat.

I was interested in PMG because they are free of the high frequency noise from the excitation system- diodes, etc.  

I settled for my ST-3 with noise suppression added to the excitation bridge, and my own low EMI AVR which uses a soft switched bipolar power transistor.  I badly needed the flicker suppression that the AVR provides, and I couldn't get that via PMG.

[RJ]

Now lets the Eagle Pitcher PMG Alternators.

I like them very much when rectified to 24 volt or 48 volts DC. They are efficent. No need to worry about 60 Hz. So voltage droop will not be a problem. These are not cheap run of the mill PMG's. I have three  Eagle Pitcher PMG's and They are very well built. I am planning to finish a system with an Eagle Pitcher in the future.  

Here is the link of the project   http://www.microcogen.info/index.php?topic=2800.0

Henry

Perhaps Henry is on to something.... Basically what I want is a dual speed long run time gen set.  One that I can spin down to 400-600 RPM at night/low demand periods then crank up to 1200 or so when high demand is in order. (ac, well pump etc... ) I have selected an engine which puts out 16hp at 1200 RPM. I would really like a 6 pole ~10kw gen head.... The engine will develop ~8hp at 600 RPM. Which is still more then I need, I'll have to see how it runs down to 400 RPM or so. Perhaps a DC alternator tied to some inverters is the way to go. I'm not sure if they make 240v output 60hz inverters... something I will have to look into.

Can a PMG be tied directly to an inverter or would I need batteries to regulate the voltage. Perhaps one of those 48v alternators is the way to go....

-Randy

[mobile_bob]

if you are wanting to run from 600 to 1200rpm, depending on load
i would go the alternator route and generate DC to charge batteries

if you don't need storage capacity, there is no need for expensive deep cycle batteries
you could easily series connect 4 twelve volt automotive batteries to get the 48volt dc required by an inverter

most if not all of the big boys make 240vac inverters 60hz so getting one is not a problem.

this leaves you with how best to generate the power, DC pm alternator or DC wound field alternator.

me? i would go with the wound field, because of the relative ease in controlling the charge stages, and not have to regulate the engine rpm's. this would allow for a simple two step control for the engine rpm, which can be done with two syncrostart solenoids, energize one for 600, the other for 1200rpm use, deenergize both and the engine shuts down.  very simple and off the shelf solution.

two modified 110-555jho alternators (upgraded rectifiers) controlled by one balmar could produce all the power the engine is able to deliver at full rpm, and do very well at the 600rpm level. the efficiency would be quite good too.

nothing wrong with the eagle picher pm alternators other than availability and price, they are costly and i am not sure they are in current production. however if you have one of them, you could do what you want to do but will need to regulate the rpm to control the charging stages.

lastly i would never recommend direct connection of an alternator to an inverter without a battery bank as a buffer. to do so leaves the inverter vulnerable to load dump voltage overshoots that could take out the front end of an expensive inverter.
the battery bank even if modest provides some protection from these voltage overshoots, which are inevitable with any alternator system, and most particularly those that rely on rpm to regulate the voltage.

you just can't go from full load, then dump the load to some fraction and have the rpm of the engine respond instantaneously.  when you dump the load, the voltage will spike momentarily (maybe even a couple seconds ) this spike is hard on any electronics connect downstream.

there also is another pleasant advantage to the use of a battery buffer, that is it will provide some measure of short term surge capacity "if" the inverter can make use of it.  for instance if you have 5kwatts of generator capacity you can only supply 5kwatts of load (save for maybe a couple seconds of surge), however the same generator connected to a 5kwatt inverter with battery buffer can provide anywhere from 7.5kwatts for a few to several  minutes, to as much as 11kwatts for several seconds depending on the inverter used and the battery banks capacity to deliver short duration surges. this is why i like automotive batteries for this scheme, even small car batteries can deliver lots of kwatts for several seconds and do so over and over again.

just a few things to consider

bob g

[RJ]

Bob, thanks for the great info!


I just did a little digging on the 110-555jho. It appears this alternator is rated at 160 amps at 12 volts, or about 2kw. So two would equate to about 4kw, which would be adequate at about the 600 RPM mark of my engine, which is rated at 8hp. You had mentioned that this setup would handle the full output power of the engine at 1200 RPM (or 16hp). Perhaps I'm missing something.

Regarding batteries. I have a few old military 24v lead acid batteries. I'm not sure of the capacity. They have never been filled with acid so they're essentially NOS. Perhaps these would do. They're about the size of an average car battery.  I have no need for a lot of storage.

I'll have to look into inverters. Perhaps best to for go the 60hs alternator all together....

[RJ]

Bob I sent you an e-mail. let me know what you think.

randy

[RJ]

Now lets the Eagle Pitcher PMG Alternators.

I like them very much when rectified to 24 volt or 48 volts DC. They are efficent. No need to worry about 60 Hz. So voltage droop will not be a problem. These are not cheap run of the mill PMG's. I have three  Eagle Pitcher PMG's and They are very well built. I am planning to finish a system with an Eagle Pitcher in the future. 

Here is the link of the project   http://www.microcogen.info/index.php?topic=2800.0

Henry

Henry did I buy all three or do I have two of these unit. I can't remember.... If you still have one did you ever further test it?

[Henry W]

RJ, did you buy the propane converted vanguard engine with one mounted? I can't remember? If you did, then you have all three.