What should I know about converting from single to three phase? The shop I work out of has only single phase. I was thinking about getting a welder and wanted to know if I could widen my options by considering a 3 phase unit and what I would need to do to run it off a single phase power. What are some sites or sources I might go to to read up on this?
- Thread starter JimS
- Start date
gene bender
Well-known Member
you need a phase converter
Mike(NEOhio)
Well-known Member
- Location
- Newbury, Ohio
I've been told a three phase motor run on single phase will generate three phase current but it will not start on single. You can couple a smaller motor to start it or even rig a rope start. I can't say if it's true or not, just something I heard.
Steve@Advance
Well-known Member
I don't see any advantage to trying to run a 3 phase (that you don't already own or have found a great deal on one) welder on single phase.
About the only advantage I could see would be balancing the line load in a factory with multiple welders and 3 phase already in place.
I've never tried running a welder on a phase converter, but I see more problems than it would be worth.
There's information out there, what I see looks complicated.
Phase Conversion
About the only advantage I could see would be balancing the line load in a factory with multiple welders and 3 phase already in place.
I've never tried running a welder on a phase converter, but I see more problems than it would be worth.
There's information out there, what I see looks complicated.
Phase Conversion
Janicholson
Well-known Member
No reason to go 3phase. The welder would then reconvert the 3phase into DC or single phase AC to weld with. Just use a solid 50 or 100 amp circuit far a 230 single phase welder. Jim
Yes, that works...I made one several years ago. I belted a small single phase to a three phase motor, with the single on a hinge so I can tighten the belt til the 3 ph is running, then disconnect. The 3 ph keeps running, and generates the third phase thru the third wire. Wire 220 hots to two of the wires, then leads from all three wires go to your 3ph machine. You can look up diagrams by googling home made 3 phase converters.
timcasbolt
Well-known Member
I have a Cedarburg rotary phase convertor. It's used to run my Bridgeport, surface grinder, and band saw. I've found it is more robust and far superior to Phase-a-matic. No idea how it would be running a welder.
buickanddeere
Well-known Member
The welder input maybe single phase 480V . Thus only a transformer, this three phase is not required ?
morgan in ar
Member
I've been an electrician for more than 20 years, I've never heard of a three phase welder before. Learn something every day.
RedMF40
Well-known Member
I'm following this because I have similar situation with a 2-post automotive lift for my home shop. Good deal on the right-size lift and it's a Benwil, good brand. Regular 240V but motor is 3 phase. Master electrician friend told me to go for it, and he'd fill me in on the details. One possibility is to run the motor as-is and it will probably operate at painstakingly slow speed. Another option is to replace the lift motor with single phase 240V. Probably much different scenario for the welder, however.
Mike(NEOhio)
Well-known Member
- Location
- Newbury, Ohio
Jim, you didn't say if it is a transformer type or motor/generator?
Stephen Newell
Well-known Member
I have doubts a phase converter would work for a welder. I have a rotary phase converter and it will turn a motor but it's not true three phase, there is capacitors that bump up the voltage on L3 to compensate but for a welder the current draw would be continuous.
Steve@Advance
Well-known Member
Red, I hope your electrician didn't tell you it would work but be slow, 'cause it won't! LOL
You can change out the motor, or use a 3 phase inverter like this one.
You do have to over size the inverter to make it work single phase.
Also must start/stop the motor with the inverter controls, not an external switch.
If you get ready to do this, post again the motor HP, voltage, amp load, figure out which inverter you need.
Inverter
You can change out the motor, or use a 3 phase inverter like this one.
You do have to over size the inverter to make it work single phase.
Also must start/stop the motor with the inverter controls, not an external switch.
If you get ready to do this, post again the motor HP, voltage, amp load, figure out which inverter you need.
Inverter
Andy Martin
Well-known Member
I've run my mill for several years this way. The rule is your idler motor needs to be at least as big as the biggest motor you want to start. My mill is three HP and my idler is 5 HP.
Years ago an electrical engineer did an analysis of this system on Fine Woodworking magazine. He claimed you could get 85% of the driven motor HP out of it.
I've heard you can use a capacitor to kick off the three phase idler but mine has a sheave on it, I just kick spin it then close the switch and it takes off.
You best bet on a welder these days is a solid state one anyway, and as others have said, single phase predominates. The only three phase welders I've come across are industrial eight packs and the old Lincoln bullet welders.
RedMF40
Well-known Member
If you get ready to do this, post again the motor HP, voltage, amp load, figure out which inverter you need.
Inverter
[/quote]
Steve, thanks for the info. Deal on the lift is pending. I'll post in Tool Talk about the specifics for my lift. Didn't want to gum up this thread with my separate issue.
Inverter
[/quote]
Steve, thanks for the info. Deal on the lift is pending. I'll post in Tool Talk about the specifics for my lift. Didn't want to gum up this thread with my separate issue.
Here's how we do it where we need to run large electric motors when there is no 3-phase power. If you need a higher voltage than 240 such as 480 volts, you first need a transformer to convert from 240 volt single phase to 480 volt single phase. You then input the 480 volt single phase into a variable frequency drive (VFD). The VFD will spit out 480 volt 3-phase. You have to figure your total amperage load and use a VFD double the size that would normally be required if you had 3-phase power already available.
dr sportster
Well-known Member
A 3 phase motor on two phases will burn out the overloads quickly [and won't spin]
buickanddeere
Well-known Member
Use a VFD to make true three phase power from single phase .
Andy Martin
Well-known Member
Are you saying you can't idle a three phase motor on single phase?
buickanddeere
Well-known Member
Inverter welders .
buickanddeere
Well-known Member
A three phase motor will operate on single phase up to 57.7% of it’s rated load .
Andy Martin
Well-known Member
OK, I can see that. but running with no load mine never gets warm even though it is generating the third phase for my mill. I've heard claims an idler motor will cause the windings to fail through vibration on the driven motor but I haven't experienced that. Of course a milling machine is seldom loaded near it's capacity for most work.
timcasbolt
Well-known Member
Not just inverter welders. Factory where I used to work had all 3 phase welders. A big ESAB mig, a Lincoln tombstone, (both on wheels) and a 250 Linde in the tool room. The logic behind it was that it was easier to move around the factory because 3 phase was everywhere.
buickanddeere
Well-known Member
Most transformer welders just use single phase . Only using two out of the three live lines .
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