| Author |
Message |
Craig Smith (Craigs) (65.202.123.254)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 1:01 pm: | |
Hi All,
Well, we survived Frances. Lost power for 6 days. I ran the old Onan 6.5 gas for the first 4 days, off and on, to keep the refrigerators cold. The Onan quit running and I had to run the MC8 on fast idle to keep the power coming. While looking for a replacement genset(the old one won't turn over even with a fresh battery, and yes it had oil), I got the idea, which I probably heard here first, to get a small diesel engine and put a large 150-200 amp 24Volt alternator on it. This would feed the 2 big 2Ds and in turn run the SW4024 inverter. Does anyone know how many horsepower I'd need to do this. I've taken a SWAG at it and came up with about 8HP. I'd look for something a little larger maybe 10-12HP. Isn't there a busnut out there that rebuilds alternators that would be a good source for the 24v alternator I'd need. Can't remember the guy's name. If anyone has done this or has any comments about this idea, please let me know.
Thanks, Craig S |
TWO DOGS (65.177.144.76)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 1:11 pm: | |
why not turn a 110/220 generator ???Harbor freight has them on sale...10,000....and why not use it going down the road with the 8v-71...can't figure out why everybody wants to use inverters.... |
cgoodwin (208.12.29.127)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 1:23 pm: | |
clean power |
Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 1:39 pm: | |
Has anyone had the courage to try one of these harbor freight genheads?
I looked at them and they scare me, like any expensive item that says "Made in China"
Gary |
Jim-Bob (12.46.52.74)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 1:41 pm: | |
Two Dogs, the problem with the 120/240 generator driven from the main engine is frequency. The generator has to turn at either 1800 or 3600 depending on whether it's a two pole (cheap) or a four pole (better) rotor. There are six pole that run at 1200 too but they are more rare.
When the main engine goes from 450 to 2100 RPMs, the frequency would change from 15 to 70 cycles (assuming it is the 1800 rpm gen end driven at crank speed).
But 12 or 24 volts DC feeds the inverter at any RPM where it is converted into 60 cycles. Just easier that way & it gives you 120 volts from the batteries when the engine is off, too. |
Sean Welsh (Sean) (66.82.9.62)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 8:50 pm: | |
"..can't figure out why everybody wants to use inverters...."
Well, let's see. I live full-time in my rig, so, in order to have all the conveniences of home (home-type entertainment system, microwave oven, icemaker, drip coffeemaker, etc.), I'd have to run a generator 24/7. I don't know about you, but I don't want to listen to a genset that constantly, or deal with the exhaust, or, for that matter, have to find a genset that is rated for 365-day-a-year, 24-hour-a-day operation. I'm sure my neighbors in the campground, where applicable, don't want to hear it either. Come to think of it, most developed campgrounds (e.g. NPS, USDA) prohibit generator operation between certain hours...
Does that help? ;-)
-Sean
p.s. As to the original post -- this is a fine idea. To figure the required HP, you'll need to know how much energy you need to supply to your loads, then add in for inverter losses, and lastly, the efficiency factor of the genset itself. There are a handful of Alternative Energy websites that provide some guidance on doing just this, although I think they more commonly focus on small gas-powered engines. Incidentally, the newer Honda gensets are actually variable-speed engines coupled to DC heads with sine-wave inverters behind them. Very efficient. |
Buswarrior (Buswarrior) (64.229.211.4)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 9:03 pm: | |
Hello Craig
Ian, please stike this, if I'm out of line.
In Busride Magazine, (www.busride.com) regular advertiser by the name of Penntex makes a 330 amp, 24 volt air cooled alternator (PX-833), as well as 12 volt ones from 130 to 350 amp.
My large transit employer uses their stuff on the 136 dedicated disabled transit buses they run with great success. Good voltage at low city RPM's is their claim to fame.
They also have their own line of external regulators.
Might be good source of new stuff for a converter.
Penntex Industries
www.penntexusa.com
As usual, no profitable benefit for me, as I am not the owner, or even know their sales guy...
Rats.
happy coaching!
buswarrior |
dwight (67.213.8.161)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 9:24 pm: | |
I think it takes like 20 h.p. for a 6000 watt gen.
(1800 rpm) so using those figures 6000/20=300 per h.p.
200 amp x 24 volt = 4800 / 300 = 16 h.p.
200 amp x 12 volt = 2400 / 300 = 8 h.p. |
Clark Lane (67.136.120.70)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 20, 2004 - 9:36 pm: | |
The new prevost conversion at FMCA rally had the setup with a generator that ran off the main engine like two dogs is talking about.Big selling point about this new feature. |
Johnny (4.174.109.203)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 21, 2004 - 1:42 am: | |
Another source for hi-power, compact alternators is Premier Power Welders. |
Craig Smith (Craigs) (65.202.123.254)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 21, 2004 - 9:35 am: | |
Thanks guys for all the input.
Craig S |
Tom Caffrey (Pvcces) (65.74.66.104)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 22, 2004 - 12:26 am: | |
Dwight, a horsepower is equal to 746 watts. I've seen a rule of thumb for engines running generators somewhere. IIRC, it was 2 hp per kw for gasoline and 1 1/2 hp per kw for diesel.
We've had the problem come up with rental equipment. There is something that can throw this way off, however. If the peak torque required by the generator occurs at too low of an engine's RPM, the engine can be bogged down an not reach its working RPM unless the load is reduced.
This problem can easily crop up with an alternator, so care must be taken to get the ratios right.
An alternator's peak torque occurs at or near the lowest speed that produces maximum current. If they are speeded up beyond that point, the torque falls off even though the current stays at maximum.
This can lead a person to think that it takes a much larger engine even though it doesn't, really. It's just a case of matching the curves.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher |
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