Rotary Phase Converters for 1 Phase + N supplies

Are you wanting to set up an artificial 3 phase system?

It can be done but it's a bit weird. I built one in the 70's using info from a 30's text book.

Have a look at inverters first. I'll see if I can find my books

Hi TonyS,

Thanks for the speedy response! I'm simply trying to power a few small machine tools with 3 phase motors... these in particular have some unfortunate characteristics... the casings are integrated into the machine + the terminal boxes do not permit reconfiguring the connections from star to delta. The inverters work well (I'm using one already) where the motor can be swapped or reconfigured... I guess the problem is budget; its a step change in price to go from an inverter that synthesises 3 phase at 240V to one that will give 400V from the same 240V supply...

Well my idea of the artificial 3 phase goes out of the window if you can't change the connections.

Just an idea to run past you, have a look for a second hand transformer. Your in Cyprus there's got to be military surplus for sale. Then inverters come back in to the equation also artificial 3 phase.

Believe me artificial 3 phase is weird but you can run a full workshop from it. In fact the more motors running from it the better it gets.

I've seen some surplus for sale... had the chance to by some nearly complete Phantom engines a couple of years back... I'd heard that once another motor was running with a rotary converter it all got better and better... until the poor old single phase cabling got too stressed... owt for nowt etc. I notice you are in Mansfield; just up the road from where I studied (Nottingham) a long time ago it seems.

I'm from Buxton, Derbyshire originally, arriving in Mansfield via a 12-year stop over in Nottingham. I'd like to go back to Nottingham though. Good pubs, music, etc.

Why didn't you buy the engines? Could have been the start of a good project!

was tempted... having had experience with Adours and RB211s in my first 'proper' job in Derby... decided my car parking spot was too small and it would be a bugger dismantling it to take it up in the elevator... Nottingham certainly had some highlights (other than having the highest crime rate in the country... in Hyson Green)... still got some friends there.

As you may well know, a 3 phase motor will not start on single phase but it will run on it. I have a 2 HP milling machine and a 7.5 HP lathe and both are started with this. The option of me getting 3 phase was far too expensive so I tried this route, 22 years ago. As described, they are quite inexpensive and as long as you aren't expecting to use the machines for any more than about 50% capacity, they work just fine.

What they do is to split a single phase leg through a switched capacitor and either by current or timing open that leg upon starting.......Or something like that. I know, one leg is dead (after starting) and the other two aren't particularly balanced, but it works for me.

The simplest way to do a 1 to 3 phase converter is to use a 3-phase squirrel-cage motor. It should be about twice heavier than the 3-phase power you need. You have to power it on one phase and start it with a phase shifter (capacitor or resistor) and then let it run freely. It will provide you 3 phases. The name of the configuration is Arno-Ferraris phase converter.

Didn't know it had a fancy name like that. But it does work, just don't catch your fingers flicking the pilot motor.

Thanks for the pdf - it looks like my dilemma is resolved on the first page! I will read it through carefully before taking any action. Great name; there is power in giving things names!