Running 3-phase gear off single-phase power.

[POD]

rather than continue to hijack another thread, I thought I would post this as a new topic. I did some research into this when I bought my lathe (actually my wife bought it for me for my 50th birthday, but that involved me doing the choosing, the buying, the drive to Sydney and towing it home, etc...), it's a big machine with a 3hp 3-phase main motor and a separate 1/8hp 3-phase motor for the coolant pump.
There are essentially 3 ways to run a 3-phase motor off single phase input. One is to use a capacitor wired into one leg of the single-phase input, and, via a momentary switch, the capacitor is used as a starter, i.e. the motor is switched on via a normal on/off switch and the momentary switch is held for about half a second to start the motor, then the motor continues to run on 2 of the 3 legs. This works in low-load situations, the motor will only produce 2/3 of it's rated power. I've wired the coolant pump motor on my lathe this way. There are diagrams for this readily available on the web.

Another way is with what's called a 'rotary phase convertor', this uses a separate 3-phase motor as an idler which, by powerful white-man magic, produces the third phase. The idler motor is generally started with a capacitor as above, or in really basic setups can be pull-started with a cord like a mower. Rotary convertors can be set up as a plug-in, wheel-around unit with a 3-phase socket (or several) that you can plug any 3-phase machine into, or multiple machines up to it's rated output. No alteration is necessary to the machine itself. These are available as commercially produced units; in fact, a good friend of mine has just established a business manufacturing these units for domestic and commercial applications. A machine plugged into one of these units will behave exactly as if connected to 3-phase mains power.

A third way is to wire the 3-phase motor via a Variable Frequency Drive (VFD) as mentioned in another thread. Like this one (incredibly cheap): eBay Australia: Buy new & used fashion, electronics & home d (http://www.ebay.com.au/itm/130654404214'ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_15112wt_1139)

These units can only run one motor, and if running an existing machine, like my lathe, from a VFD the machine has to be re-wired so that the single-phase input goes into the VFD input, the VFD output goes directly to the 3-phase motor, and all switching is done via the VFD. I stripped all the 3-phase wiring out of my lathe and re-wired the machine so that the original switches now act as controls for the low-voltage switching circuitry of the VFD. You can't just set it up to plug a machine into, as you can't have any switching between the VFD's 3-phase output and the motor. A benefit of the VFD is that it provides a speed control for the motor, which is a boon on machines like lathes and big drill presses etc.

I'm surprised more people with home workshops aren't aware of this stuff. My neighbour sold his 3-phase lathe when he moved here as he couldn't run it, he was spewing when I showed him my 3-phase lathe running off single-phase power. Again, there's heaps of info on all these methods on the interweb.

[Blknight.aus]

Just gotta watch the power draw and the motors start up current.

you can in a pinch on some electric motors just wire up the single phase and so long as you give them a rolling start and let them get up to speed they'll work.

[steveG]

POD, how efficient are they - ie what rating single phase input do you need to run for a 3hp motor like you're using?

Steve

[Graeme]

One of my sons uses a VFD for his mill, having recently moved from a 3-phase site to single phase. He just has to start it slowly to avoid current overload.

[Killer]

[QUOTE=POD;1852527] You can't just set it up to plug a machine into, as you can't have any switching between the VFD's 3-phase output and the motor. QUOTE]

You can, but you run into complications with the switching contactors on the machine. If you have the VVF controller set to the standard frequency and voltage of the machine, you can have the controller running continously, and operate the machine as normal. You would be able to run the coolant pump as well under this system.

Cheers, Mick.

[Bigbjorn]

Yonks ago when Brisbane City Council was our electricity supplier, I acquired a large Mars lathe (three tons) which had a three phase motor of around 4 horsepower.
I applied to the electricity dept. to have a three phase service connected. I was told I had to first apply to town planning. Town planning virtually refused then to permit three phase in a residential A zoning unless you were up a long easement and voltage drop was a factor. They feared you were going to be running a factory or business in a Res. A zone. I eventually acquired a used 240 volt motor of quite some age and physical size, 4.5 horsepower. Starting up caused lights to brown out and tv picture to momentarily reduce to postage stamp size. I had good neighbours who were amused rather than annoyed. Besides I did their little machining jobs. The electricity dept. said the solution was for them to fit a residential pole transformer on my service. They gave me a quote which shocked me and I didn't go ahead, just kept using the existing supply.

[rovercare]

Just gotta watch the power draw and the motors start up current.

you can in a pinch on some electric motors just wire up the single phase and so long as you give them a rolling start and let them get up to speed they'll work.

Pffft.

[rovercare]

Phase convertors are the best, you can buy one just up the road in longwarry:D

With 2 phase you can "growl" a motor, but it's pretty crude, with one phase you ain't doing lick, without a vsd or converter

Single phase to 3 phase vsd's only go up in size so much

[Blknight.aus]

a star wound single phase motor will run on a single phase, just, if you get it started...

Wouldnt want to be using it to try and drive a compressor.

[Hymie]

Phase convertors are the best, you can buy one just up the road in longwarry:D


A mutual friend also makes them in Drouin Matt.

[POD]

As mentioned earlier, you can run a 3-phase motor on a single phase, but you have to have a means of starting it- e.g. pull start or capacitor- and it will only run at 2/3 rated power. There is a technique for wiring the third leg via 'run capacitors' as well as 'start capacitors' so that the motor will operate more smoothly (another form of white-man magic) but I think this still produces 2/3 rated output.

My 3hp lathe motor is actually running on a VFD rated to 2hp that was given to me by a friend. Not an issue in general use, but would not be able to run at full load such as heavy cuts on large diameters. I'm running it off a 20 amp circuit that I had installed for my welder. A lot of VFDs require 3-phase input for 3-phase output, something to watch out for if buying. One of the things with these gadgets is you can program all sorts of running parameters such as spool-up time, gradual slow-down to stop, emergency stop which uses electrical braking, forward & reverse, speed control etc.
I'm not by any means an expert in the subject, just did a bit of reading and internet research for my own purposes. I don't know how the current draw would compare between the various arrangements. The reading I did made it pretty clear that having switches between the VFD output and the motor input would be detrimental to the VFD, my understanding was one motor, one VFD.

[steveG]

Phase convertors are the best, you can buy one just up the road in longwarry:D

With 2 phase you can "growl" a motor, but it's pretty crude, with one phase you ain't doing lick, without a vsd or converter

Single phase to 3 phase vsd's only go up in size so much

In the 3-5HP range (which is all I could ever see myself using), what advantages does a phase converter have over vsd?

Ebay has Aussie made 3HP converters like this (http://www.ebay.com.au/itm/Single-to-three-phase-converter240V-to-415V-3HP-2-2KW-Complete-and-Ready-/251157100769) for around $1600, which is a LOT more than a 3HP VFD.
I note that you can run welders on them (up to 450A on that $1600 one), whereas internet opinion seems to be you can't run a welder on a VFD.

Still a high premium to pay for having that flexibility - there must be more to it than that...

Steve

[POD]

I think the main thing is that with a phase-converter you can plug any machine, or multiple machines, into the unit up to it's rated output. Good for a workshop that runs several machines, including welders as you mention. A VFD is dedicated to one piece of equipment. Also with a phase converter, no modification is needed to the machine.

[rovercare]

I think the main thing is that with a phase-converter you can plug any machine, or multiple machines, into the unit up to it's rated output. Good for a workshop that runs several machines, including welders as you mention. A VFD is dedicated to one piece of equipment. Also with a phase converter, no modification is needed to the machine.

That

Single phase to 3 phase vsd's have a high failure rate from my experience, that's Allen Bradley gear, so not rubbish

Running a 3 phase motor on star limits torque and trying to crudely make it growl will see another drop, then using a phase and neutral as opposed to 2 phases is even worse

Single Phase motors are extremely cheap these days also
Making a motor turn is different to making it do "work"

[roverrescue]

Matt,
My shed has two phases to it?
If I happened along some 3 phase gear - how much hassle is it to jigger the power to run it?
Just thinking thats all? Would most likely be a mill or hori bandsaw.

S

[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.

[isuzurover]

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.

This website has a very good explanation.
What You Might Want to Know About Electricity Before You Talk to Your Electrician (http://www.thecoffeebrewers.com/electricity.html)

[warren9981]

Power companies in our area won't install 3 phase either for the reasons listed above, however, if you are planning to install a 3 phase air-conditioner to your house they will install the power for you. Hmmm, then have a source for 3 phase. ;-)

[DoubleChevron]

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.

I think a lot of old farms have this. It's not true 3phase. One of my mates has it on his farm. You can get away with far less current pull using "two phase". I pretty sure the phases are 180degrees apart... they must be the two sides off a center tapped trannie (I'm sure google would give the answer in seconds if you searched). I've seen old 240volt motors that have wiring instructions/tappings for 2phase.

I made myself a phase converter for a big grinder a while back. You need to have the correct 3phase motors. They need to be wired delta @ 240 across the phases from memory (check that, don't trust my memory). It worked ok, I just pull started the 2nd motor with a rope around it's pulley. Using cap start too run the 3phase motor ... it just didn't sound happy.

Honestly though?? 3hp motors are cheap in single phase these days .... it's probably going to be cheaper and less hassle just to by the single phase motor to suite. I did miss out on a 5hp single phase (monster sized ancient job) at the closedown of a motor rewinders a couple of years back. I'm still kicking myself for not grabbing it. Imagine the compressor I could run with that :twisted: I'd have to switch off everything in the shed to start it though .... could you imagine the startup current pulled by a 5hp motor :eek: The compressor used to dim half the street with a 3hp motor.

seeya,
Shane L.

[SuperMono]

A third way is to wire the 3-phase motor via a Variable Frequency Drive (VFD) as mentioned in another thread. Like this one (incredibly cheap): eBay Australia: Buy new & used fashion, electronics & home d (http://www.ebay.com.au/itm/130654404214'ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_15112wt_1139)


In a domestic situation be aware that using a VFD is likely to drive someone nearby nuts through the RFI getting into their radio or TV enjoyment.
Technically if you buy something like this from overseas you are now also the importer and responsible for all compliance issues like C-Tick.
Chances of coming unstuck legally are minimal, more likely to face the RFI complaints during the cricket.

[rovercare]

Matt,
My shed has two phases to it?
If I happened along some 3 phase gear - how much hassle is it to jigger the power to run it?
Just thinking thats all? Would most likely be a mill or hori bandsaw.

S

Easy, if its a machine with one motor and bugger all control gear, purchase a single phase motor:D

[rovercare]

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:D

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

[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.

[Bigbjorn]

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.

[rovercare]

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

[Disco44]

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

[rovercare]

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

:eek: would you like a resume?

[2stroke]

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...

[rovercare]

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

[POD]

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

Well, I hope I have not appeared to representing myself as an expert on this subject, everything I know about this has come from either the internet or conversations with others, and my own very limited experience with one machine. I posted what info I have simply to raise awareness of the possibilities, as a lot of very good, cheap, heavy-duty second hand machinery is overlooked by people like me with a home workshop, on the assumption that they cannot run it.
There wouldn't be much discussion on these forums if everyone had to pass an exam before entering a conversation.

[Sheppie]

[QUOTE=DoubleChevron;1854253]I think a lot of old farms have this. It's not true 3phase. One of my mates has it on his farm. You can get away with far less current pull using "two phase". I pretty sure the phases are 180degrees apart... they must be the two sides off a center tapped trannie (I'm sure google would give the answer in seconds if you searched). I've seen old 240volt motors that have wiring instructions/tappings for 2phase.

I made myself a phase converter for a big grinder a while back. You need to have the correct 3phase motors. They need to be wired delta @ 240 across the phases from memory (check that, don't trust my memory). It worked ok, I just pull started the 2nd motor with a rope around it's pulley. Using cap start too run the 3phase motor ... it just didn't sound happy.

Honestly though?? 3hp motors are cheap in single phase these days .... it's probably going to be cheaper and less hassle just to by the single phase motor to suite. I did miss out on a 5hp single phase (monster sized ancient job) at the closedown of a motor rewinders a couple of years back. I'm still kicking myself for not grabbing it. Imagine the compressor I could run with that :twisted: I'd have to switch off everything in the shed to start it though .... could you imagine the startup current pulled by a 5hp motor :eek: The compressor used to dim half the street with a 3hp motor.


I have a brand new 5HP single phase motor if anyone wants it.
I was going to put it on my car hoist but I moved and now have 3 phase power :)
Love it.
Anyway, the 5HP is for sale if anyone is interested. I paid $700 for it.
Make an offer. A realistic one please.
on another note, 3hp (2.1kW) VSD's are pretty good, Ive got one of these as well. Having frequency speed control beats changing belt configuration every time you want to slow down or speed up your lathe. Its not used anymore since im now on 3 phase.
Cheers,
Phil

[wrinklearthur]

I'm a bit vague on how it was done, the fitter and turner not far from me has a thumping big lathe in his shed and only has single phase to the shed.

Noting this, I asked him how did he run it?

Well, he went over and checked all was clear, then turned a key, a engine started and then using a automatic shifter, selected a forward gear and away the lathe rotated.

The power source is a old Cortina and he has permanently set the car up next to the shed and drives the gear inside with a shaft connected to the back axle.

It's impressive way to get around the problem, but it did cost him a new car for his wife at the time, less an amount for a no trade in deal. :p
.

[rovercare]

I'm a bit vague on how it was done, the fitter and turner not far from me has a thumping big lathe in his shed and only has single phase to the shed.

Noting this, I asked him how did he run it?

Well, he went over and checked all was clear, then turned a key, a engine started and then using a automatic shifter, selected a forward gear and away the lathe rotated.

The power source is a old Cortina and he has permanently set the car up next to the shed and drives the gear inside with a shaft connected to the back axle.

It's impressive way to get around the problem, but it did cost him a new car for his wife at the time, less an amount for a no trade in deal. :p
.

I was at an old dairy the other day, still had the functional pro input for the milk pump for power outages:D

[Vern]

Geoff 'junior' hallidays dairy I presume. I seen that as well a while back. You must have been fixing the job I couldn't get to.

[Blknight.aus]

I was at an old dairy the other day, still had the functional pro input for the milk pump for power outages:D

Pro or PTO?

[rovercare]

Pro or PTO?

PTO

On a phone, just back from monash with surgery on the newborn young fella, so proof reading hardly took priority

[rovercare]

Geoff 'junior' hallidays dairy I presume. I seen that as well a while back. You must have been fixing the job I couldn't get to.

Yes

[steveG]

PTO

On a phone, just back from monash with surgery on the newborn young fella, so proof reading hardly took priority

That's not too good Matt - hope he's doing OK.

Steve

[rovercare]

That's not too good Matt - hope he's doing OK.

Steve

All is good now, discharged back home etc, wife went through a bit. 3 months of terrible pelvic instability, 12 hrs labour the emergency c section, then off to monash to get his nuts fixed up! No more breeding, I'll be off to see the surgeon and have mine fixed up soon

9 pound 14 ounces out of a girl that's normally 54kg ringing wet is an ask

[wrinklearthur]

All is good now, discharged back home etc, wife went through a bit. 3 months of terrible pelvic instability, 12 hrs labour the emergency c section, then off to monash to get his nuts fixed up! No more breeding, I'll be off to see the surgeon and have mine fixed up soon

9 pound 14 ounces out of a girl that's normally 54kg ringing wet is an ask

Ouch! poor mum, hope all are doing better now.
.