Thread: Running 3-phase gear off single-phase power.

Originally Posted by POD

I've never understood what is meant by 2-phase power. I have single-phase power yet there is a bore pump (50m down a hole) wired from my shed that I've been told runs off 2 phases. This is a mystery to me. After a bit of reading, I kind-of understand the concept and purpose of 3-phase power, but that's stretching it.

There is 2 types of 2 phase power

1. 2 phases from a 3 phase transformer, sign wave 120* out of phase to each other

2. centre tap transformer, grabbing both legs, its actually commonly known (atlease in Vic) as 480V or farm supply, sign wave 180* out of phase to each other....These are sommonly from a SWER (single wire earth return transformer, from a single phase

Lots of Rural areas use this, lots of old dairy's had 2 phase 480V motors, which know single phase stuff is alot better are never seen new

As an industrial breakdown sparky, I get to replace motors regularly which didn't have good 3 phase supply (once the smoke gets out you can't put it back, won't run without the smoke in). Never seen a "phase converter", industrial customers always have 3 phase supply available, sounds pretty fishy to be honest.
Single phase to 3 phase VFds are common and cheap but only up to around 1.1 kw. Price goes up from there. They only output 220v 3phase so you need to connect a 415v motor in delta (often chinese motors are internally connected in star and the motor needs to come apart to do this). Big single phase motor might be the easiest.
Either way, remember you're playing with power.
Edit, if you change the motor you might still find the lathe has a control transformer that's 415 to something lower and will not work on 240v supply.

One of those phase converters might be a proposition if your machine has an integral motor which can not readily be replaced with something else. If, however, your motor is freestanding or separate and drives the machine via belts or other transmission devices then buying an appropriate 240 volt motor is likely cheaper.

My experiences at auctions are that 240 volt machines fetch quite a bit more than three phase machines. This made me think that if buying new machines and a 240 volt version is available at little or lower cost, then buy the 240 volt jobbie for the better resale value.

Three phase motors have little resale value. I have seen pallets of them go at auction for $200 - $400.

Originally Posted by 2stroke

As an industrial breakdown sparky, I get to replace motors regularly which didn't have good 3 phase supply (once the smoke gets out you can't put it back, won't run without the smoke in). Never seen a "phase converter", industrial customers always have 3 phase supply available, sounds pretty fishy to be honest.
Single phase to 3 phase VFds are common and cheap but only up to around 1.1 kw. Price goes up from there. They only output 220v 3phase so you need to connect a 415v motor in delta (often chinese motors are internally connected in star and the motor needs to come apart to do this). Big single phase motor might be the easiest.
Either way, remember you're playing with power.
Edit, if you change the motor you might still find the lathe has a control transformer that's 415 to something lower and will not work on 240v supply.

Phase converters are very legitimate devices, I've sold a couple and know of a few more that are a decade or so and forever faithful

Best you do some reading on them

Originally Posted by 2stroke

As an industrial breakdown sparky, I get to replace motors regularly which didn't have good 3 phase supply (once the smoke gets out you can't put it back, won't run without the smoke in). Never seen a "phase converter", industrial customers always have 3 phase supply available, sounds pretty fishy to be honest.
Single phase to 3 phase VFds are common and cheap but only up to around 1.1 kw. Price goes up from there. They only output 220v 3phase so you need to connect a 415v motor in delta (often chinese motors are internally connected in star and the motor needs to come apart to do this). Big single phase motor might be the easiest.
Either way, remember you're playing with power.
Edit, if you change the motor you might still find the lathe has a control transformer that's 415 to something lower and will not work on 240v supply.

You sound to me like someone who knows what he is talking about.I think a lot of answers on here appear to have come from experts who got it all out of a book.Lots of them around and they are dangerous,
John

Originally Posted by Disco44

You sound to me like someone who knows what he is talking about.I think a lot of answers on here appear to have come from experts who got it all out of a book.Lots of them around and they are dangerous,
John

would you like a resume?

Originally Posted by rovercare

Phase converters are very legitimate devices, I've sold a couple and know of a few more that are a decade or so and forever faithful

Best you do some reading on them

Okay, read it, for the money I'd rather a 240v motor or a VSD, and the change. After 10 years I guess it must work but...

Originally Posted by 2stroke

Okay, read it, for the money I'd rather a 240v motor or a VSD, and the change. After 10 years I guess it must work but...

The places I've used them have multiple lathes and mills, so it's a more economical solution

One if the long term units I speak off has 3 lathes, 2 mills, crank grinder, cylindrical grinder, camshaft grinder and 3 phase welder