# modifying 3phase gensets for lower speed??



## Tirediron (Jul 12, 2010)

I have a couple of older (80s) 150 ish KVA gensets, 60 cycles @ 1800 rpm , I am curious if I could pull off different points or something to get 60 cycles @900 rpm for low load situations , and still be able to switch back to 1800 rpm for more load. :scratch


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## longtime (Nov 22, 2009)

The 1800 rpm gets you 60 cycle. If you drop to 900 rpm the frequency will also drop to 30 cycles. 1800 rpm is nice and slow, but 150 KVA is very large and wastefull for just a couple KW that most people will need most of the time. You might try to sell them and buy something better suited for your needs.

I have two sets wired to my house, a 6.5 KW for low loads and a 25 KW for full capacity (including my shop).


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## ZoomZoom (Dec 18, 2009)

I agree with longtime.

I have a couple 225 KW gensets that are just too big for most of my application needs. A smaller one gets everything done.

If you do want to use it, keep it at 1800 RPM's. I'm assuming a main reason you want to drop it down is fuel savings. By reducing your load, it'll inherently burn less fuel. On my large generator, it uses 44 gallons per hour at fuel load. Under low load or no load but at the same RPM's, it drops down to 11 gallons per hour.


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## JeepHammer (Oct 10, 2008)

I use batteries and solar panels for low consumption,
Go with Welder/Generator for higher loads in the shop, like heavy welding or machining.

I have an Onan low RPM genset for house backup.
Works VERY well. Swiped from an old motor home, so it's sized about right.


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## nj_m715 (Oct 31, 2008)

If you are using it many hours a day to power small loads, you might be able to run it less if you charge some golf cart bateries. run down the batteries and recharge as needed. Only run it to charge the batteries or power a large load for a short time. 
It would also be the start of a solar / wind system. Check ebay/ craigslist for cheap panels and build it as time/money allows. 
I know it doesn't answer your question, but it's just a suggestion.


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## Tirediron (Jul 12, 2010)

WTF after all of the replies to "how a generator works" I get the get a smaller gen answer . 
IT's 3 phase, it must have other tap points to be able to pull 60 cycles at ditferent speeds


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## longtime (Nov 22, 2009)

Don't get pissed, it's three phase, that means it has three 120 volts to ground legs not the two that you have in you house. You can use it for single phase applications (try to keep it balanced). But there is no way to get 60 cycles out of it at 900 rpm without buying a frequency changer$$$$$$$

If you are pissed, I suggest that you learn how a generator works. we are tired of trying to educate.

Won't be returning to this thread!


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## Tirediron (Jul 12, 2010)

longtime said:


> Don't get pissed, it's three phase, that means it has three 120 volts to ground legs not the two that you have in you house. You can use it for single phase applications (try to keep it balanced). But there is no way to get 60 cycles out of it at 900 rpm without buying a frequency changer$$$$$$$
> 
> If you are pissed, I suggest that you learn how a generator works. we are tired of trying to educate.
> 
> Won't be returning to this thread!


Single phase is 1 120 v


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