Single phase motor from 2 phases possible?

[Hood]

Is it possible to run a single phase induction motor from 2 phases of a 3 phase supply? I was at first thinking a small transformer to drop down from 415v to 230v would work but then thought that the single phase motor might not be happy on that.
Is it possible to do?

 

[8ob]

Is it possible to run a single phase induction motor from 2 phases of a 3 phase supply? I was at first thinking a small transformer to drop down from 415v to 230v would work but then thought that the single phase motor might not be happy on that.
Is it possible to do?

Cant you find a neutral anywhere?

Bob

 

[Hood]

I could but it was just that the Stealth Tig I have has an output socket on the back for a cooler and it would be nice to plug my cooler into it so that they both operate together and that way some idiot wouldn't forget to switch the cooler on

I was going to just use a 3 phase motor on the cooler but as there are only 2 phases present on the welders socket that would mean I would have to fit a capacitor of some sort and have never done done that before.

 

[WorkshopChris]

In theory it should be ok as the cooling fan motors in older welder are often on a tapping of off a 3 phase transformer. Although a fan is running a lot less load than a pump.
(In my head at the moment i am struggling to see the AC waveform the motor would see)

EDIT. Just thinking are there any difference in a US 220v motor and our 230v motors in the way they are wound? as they would be running 2 phases of a 110v supply?

 

[Hood]

Are the fan motors conventional single phase motors though? I don't think they have a capacitor to start them but then maybe with the two phases they don't require one? But yes as you say there would be 120 degrees between the phases one way and then 240 to get back again.

 

[bwservices]

simaco do a 2 phase 400v pump

 

[Luke]

Phase to phase is 415 V. Phase to Neutral is 230 V. They are not the same thing!

If you need 230V and don't have a Neutral, use an isolating 415/230 V transformer. If you tie one of the secondary outputs to ground, this becomes your new Neutral, for the 230 V load on the transformer (Only, not any other loads).

 

[MattH]

Phase to phase is 415 V. Phase to Neutral is 230 V. They are not the same thing!

If you need 230V and don't have a Neutral, use an isolating 415/230 V transformer. If you tie one of the secondary outputs to ground, this becomes your new Neutral, for the 230 V load on the transformer (Only, not any other loads).

Yes, what Luke said.

I was surprised to find my mill doesn’t have a neutral even with all the CNC controls.
Turned out the 415v is fed to an isolating transformer with an output tied to ground to act and the new neutral which then feeds all the additional CNC equipment.

 

[Luke]

It's pretty common in industry. We can end up having to derive 230 V and 115 V supplies from a 415 V supply without a Neutral.

 

[Hood]

simaco do a 2 phase 400v pump

Thanks, will maybe lookout for one at some stage but not at themoment, funds are limited

Phase to phase is 415 V. Phase to Neutral is 230 V. They are not the same thing!

If you need 230V and don't have a Neutral, use an isolating 415/230 V transformer. If you tie one of the secondary outputs to ground, this becomes your new Neutral, for the 230 V load on the transformer (Only, not any other loads).

Yes I know that phase to phase is 415v hence the reason I mentioned a transformer but also the reason I said I didn't think it would work as although it was dropped to 230v between phases it would still be two phases.
However the second part is exactly what I was looking for, thanks.

 

[Pete.]

Going on from what Luke said if all you're doing is running a motor then wiring the primary of a normal yellow box portable site transformer across two phases will yield approx 198V at the secondary and they nearly all have a centre-tapping on the secondary that you can bring to earth (which is how they get the +55v/-55v output in normal use). You'll end up with the 'neutral' output at -100V but if it's just powering a motor then the motor won't care.

I can't see any problem with this but one of the more electrical-savvy might say it's a no-no.

 

[bwservices]

you might be 50 quid richer in a weeks time?
https://www.ebay.de/itm/Wasserpumpe...332602?hash=item23ae9c467a:g:cvUAAOSwikpb5bnJ

 

[Stueeee]

My BOC ADR 300 TIG welder has a two phase motor for the internal fan, which is about 12" diameter. When the fan motor went sizzle phut several years ago, I had to get it rewound as I couldn't find a similar replacement and the massive flexible supply lead on the welder doesn't have a neutral.

However, the point is that apart from having 415V windings, it was a bog standard 4 pole capacitor start motor with a centrifugal switch for the starting capacitor, so from that I assumed that there isn't sufficient phase rotation from two phases to run a plain induction motor properly.