Generator size for rotary phase converter

OK, if you are looking for at a generator, I assume that you don't already have one. So why not get a 3 phase generator and skip the rotary phase converter all together? IF the generator is 208 3 phase, each phase to ground/neutral is 120 volts so you have your 120 power source covered. And depending on the generator some can be wired 240 3 phase. These are typically 12 wire generators and can by wired in any configuration up to 480. But unless you have equipment that is specifically 240 volts, then I would skip the rotary converter all together, get a 3 phase generator and be done with it.
 
The idea of a three phase generator crossed my mind too.. (Great minds)..... I have been actively looking for a surplus military generator..
MEP- 803A this is a 10 kw single or three phase generator ... this I believe, will be the answer to all my problems....

unless you can recommend a better three phase generator...
 
Can you rent a generator similar in size to what you are thinking of purchasing? Try it out and see how well it works.
 
Not familiar with these gen sets, as opposed to the more common brand names. Certainly sounds like these military units should work well. My question on the MEP-803A is it does not show that it can be switched to 240 three phase. I shows 120/208 three phase with the ability to adjust the voltage to 220V which may be enough? This also effects the amp draw, from what I have seen elsewhere you would need a minimum of a 15KVA+ generator to start a 7.5Hp motor. See reference.
http://www.nationalpump.com.au/calculators/guide-to-choosing-generator-to-motor-size/
Gen Spec.jpg
 
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like said above by chipper5783, before i spend any money i will be testing out the setup with a rental i am hoping....
well now with second thought that may be too close to the upper end of the three phase......
I think my balloon just popped....
 
It's really going to depend on what you are doing. If it's a temporary setup then any 3 phase generator should be fine. If you are looking to do this 8 hours a day for months at a time you want a prime power rated generator. This means the gen set is rated to be run as a primary power source and not just a backup generator for a few hours a year. They are different animals. You will not find a prime rate d unit with anything close to a lawnmower engine. And the engine sizing is typically double. My prime rated RV gen set is 4000 watts and has a 16 hp Onan twin on it. A typical 4000 watt gen set has a 6 or 8 to Briggs on it. Hope that helps
 
My little shop is in a storage area. I have two spaces giving me about a 600 square foot shop.. NO 220/240 is available.... not gonna run 8 hrs a day, but if I want to make apart would like to be able to fire up the lathe...
7.5 HP biggest piece I have everything else is max 2HP...
think maybe a smaller lathe might be the only way to go....
 
Home Depot and others sell wire,run anther hot lead from the house. Even pro done would probably be cheaper/more reliable than gen with RPC.
Whole lot less noise.
 
timcki,
I have a MEP-003A milsurp diesel generator. Got it for the winters up here in Wisconsin. It is a 10kw and have it professionally wired as a whole house back up power source. It easily runs the entire house (A/C, lights, etc all on or running) plus the shop (AR 7.5 HP RPC, lights, single phase machines, and multiple 3 phase machines all running. Added all the loads up on paper and it looked like it would handle anything I had. I was curious how well it would handle it. One by one turned on everything I could. No real difference in the sound from idle to full load.
In a power outage I shut off the main breaker for the house, start the generator, flip an interlock switch at the generator then another on the main panel. Then the generator power is fed into the main panel and sub-panel for the shop.

The MEP-003 will also produce 3 phase directly. I've never done it though. Have to pull out the manual to see what the voltage is in 3 phase.
 
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