PMG who's to buy

[billswan]

I'm not offended rob, most people would have a very hard time doing that. but the crumptater busts my chops everytime i say something he doesn't like. that's what my comment was about.

  Scott R.

By gosh thats right, I have not seen any posts from him in a while.

I went and just checked his last post it was back on august 24 and it contained this line "Health has not been good - I've spent over a month in bed"

Hope you are ok out there crumptie I miss getting chewed out by you.

Ok side tracked another thread bad bill bad ...................

Billswan

[billswan]

Checked crumptie's stats one more time this morning and noticed he has not been here since august 26.

I guess that probably says something.

Anyone know anything about him?

He was a moderator.................

Billswan

[wagspe208]

I just want to be sure I am on the right track here...
So, I have an 8/1. This means I should be able to pull 4kw.
Is there a disadvantage to getting a 7.5 KW gen? If I do not overload my usage... or meaning if I only use 4kw of power my engine will pull the gen, correct? Or put another way... a 4 kw generator and a 7.5 kw generator will take the same amount of HP to produce the 4kw??
(I am planning on updating to a twin in the future, and don't want to buy 2 gens if I don't have to)
Thanks for helping a new guy.
Wags

[AdeV]

I just want to be sure I am on the right track here...
So, I have an 8/1. This means I should be able to pull 4kw.
Is there a disadvantage to getting a 7.5 KW gen? If I do not overload my usage... or meaning if I only use 4kw of power my engine will pull the gen, correct? Or put another way... a 4 kw generator and a 7.5 kw generator will take the same amount of HP to produce the 4kw??
(I am planning on updating to a twin in the future, and don't want to buy 2 gens if I don't have to)
Thanks for helping a new guy.

In theory, you'll lose a little bit of efficiency (alternators, like diesels, apparently like to be well loaded). On the other hand, you'll gain the ability to start hard-starting loads which take a spike of >4kw - the flywheels will cover that off - so long as your constant load is 4kW or less.

Personally, if I had an 8/1, I'd cheerfully run a 7.5kw gen head on it.

[Henry W]

Losing some efficency on running a slightly larger gen-head can be heavily debated. I found when running a 12kw gen-head at 7.5kw it showed no loss in efficency. A matter of fact efficency might be better on a 12kw gen-head running it at 7.5kw than using an 7.5kw gen-head running it at full load.

Henry

[Crofter]

Another advantage to having a larger gen head than the engine can drive fully loaded, is that you dont have to be so carefull not to smoke the gen by overloading one 110 leg of a center tapped 220 system.

[wagspe208]

Ah... I did not think about the start up loads and overloading. Thanks for the input. I will get the 7.5 kw piece. It gives me room to grow.
How do I check to see if the les are balanced? Just an amp meter after setup? Or calculate?
Thanks again.
Wags

[Crofter]

Usually just calculating loads roughly. They dont need perfect balance though some generators give out with a very pronounced growl when only one leg is loaded. It seems in them the two poles producing a single 110 output happen to be 90 deg. to each other not at 180. B Swartz has a thread on finding the problem and reconnecting the leads in a more user friendly and quieter mode.

If I am pulling the full 5 KWs balanced load on my 10-1 reduced to about 9 hp at 900 rpm I dont need to worry and black exhaust smoke will tell me I am at the limit. If I was pulling 3 or 4KW from only a single leg it would be no load for the engine but would be exceeding the amperage limit of the one loaded winding.

To do over again, for the difference in price I would jump up one or two sizes in gen head

[Henry W]

I was very happy with the ST-12 hooked up to an S195. I overloaded the S195 many times on purpose and never had the gen-head get noticibly warm. I feel it is best to oversize some. The generator head was quiet. No growning noise at all.

Henry

[wagspe208]

So everyone think the 7.5 from georgia gen is the way to go for me? Or am I missing something else?
Thanks
Wags

[mobile_bob]

for an 8hp engine the st7.5 is about minimum i would consider, you might look into stepping up to an st10 or even an st12
which would be a bit of overkill however we have some evidence that would indicate that the st12 might be a percent or two
more efficient than an st7.5

so if the price for the larger unit is acceptable, you might consider getting the larger head

one thing for sure, you will never overpower an st10, or an st12 even if you loaded it all on one leg, with an 8hp engine.

bob g

[wagspe208]

I was looking at the PMG gen heads. I hear they have "cleaner power". Is that true? The st pieces are ceretainly cheaper. Are the PM pieces worth 2x the cost?
Here is what I was looking at.
http://cgi.ebay.com/6-5-KW-Rare-Earth-Permanent-Magnet-Generator-Alternator-/160499729388?pt=BI_Generators&hash=item255e8783ec
Wags

[mbryner]

heck, wags, I run a 7.5 kw ST from a 6/1.   The upfront cost difference was negligible and really the only difference  in efficiency is keeping the slightly heavier 7.5 spinning.

As far as a PMG, look at Utterpower.com.

[sailawayrb]

I was looking at the PMG gen heads. I hear they have "cleaner power". Is that true? The st pieces are ceretainly cheaper. Are the PM pieces worth 2x the cost?
Here is what I was looking at.
http://cgi.ebay.com/6-5-KW-Rare-Earth-Permanent-Magnet-Generator-Alternator-/160499729388?pt=BI_Generators&hash=item255e8783ec
Wags

The 6/1 and ST combination exhibits the infamous 5ish HZ incandescent light flicker, but this is the consequence of the  6/1 power stroke and not the ST.  I would think the 6/1 and PMG combination would result in a similar situation, but I don't have one and can't confirm.  Perhaps someone who has one can comment about this.  Other than the incandescent light flicker which can be solved by using compact fluorescent lights, this "noisy ST power" runs everything for me quite well.

Like Mbryner suggested, I would look to Utterpower if considering a PMG.  George has a good reputation with this gang.

[bschwartz]

I've run both, and I think the PMG has a cleaner output.  The microwave doesn't buzz as much on the PMG, power output is a little higher, and voltages are quite stable.  But.... flicker is only slightly better if at all, and everything from computers and TVs to refrigerators run just fine on the ST head.  If the flicker bothers you, just use higher wattage bulbs.  Yes they will suck up all your juice, but they don't flicker as much