2 phase vs 3 phase welders

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Can someone explain why I've been told that 3 phase welders are better than 2 phase (some people call it single phase)? I can sort of understand the idea for a regular old style transformer type welder and the diode bridge but within the voltage limits of 2 phase supplies and with inverter technology, is there any real difference? After being 'processed' by the electronics in an inverter machine the output should be the same so where is the difference or is there one? Is it that the 3 phase supply is more efficient and therefore more cost effective?
Reply:http://en.wikipedia.org/wiki/Three-phase_electric_powerThermal Arc Fabricator 2101970 Lincoln RedfaceMiller 150 STLStill need a Syncrowave and a plasma and a milling machine and a lathe and a bigger shop and a....
Reply:Originally Posted by laverne3ca Is it that the 3 phase supply is more efficient and therefore more cost effective?
Reply:While the above offers a very good explanation of 3 phase power, it does not seem to answer your specific question.Forget "2 phase". Welders are available as single phase or three phase. While three phase residential power was common many years ago, particularly in the north east, that is no longer the case. It can be had but the cost is generally prohibitive. So if you are talking residential, you will need a single phase powered welder. You must also pay attention to your residential service to be sure that you have enough "available" power for the welder without overloading your service. Most standard new residentilal service is 200 amps. A very large residence might have 300 or even 400 amp service, but the standard for most residences is 200. Older residences may have 100 or even 60 amp service if the house was built in the '50s or '60s or earlier. Three phase power is generally for commercial use and is more economical for heavy loads. It also provides much higher levels of power for commercial companies. In summary, if you are looking for a residential welder, look for one that uses single phase power and make sure that your service is large enough to handle it. Inverter welders are great and loaded with features. They are lighter weight and use much less power for a given output, but they are much more expensive. Happy welding.Last edited by davido30093; 12-23-2011 at 09:07 AM.
Reply:To add on to that, a lot of guys start digging around online and come across the idea to run a phase converter and then they are set for three phase welder.  This is generally not so.  The quality of the three phase generated by a converter is not suitable to run a welder, plasma, or other "electronic" type equipment.
Reply:My shop is supplied with 575 vac, 3 phase, and my inverter welder uses what I think is technically 2 phase, L1 @ 120v, L2 @ 120v and a neutral from the utilities transformer that supplies lights etc. so that across L1 and L2 there is 240 vac and yes, the power bill here is less than at home but I only wish the industrial power was that much less expensive here. I recognize that you generally can't get more than 240 volts as 'single' phase and I more or less understand the losses in transformers so my question really is, is the a three phase welder inherently more efficient or is it just the power supply?
Reply:Regardless of what an inverter "should" do, they are apparently smoother on 3 phase and they draw a lot less current on 3 phase regardless of whether they are transformer or inverter machines.However, unless you have an active 3 phase feed to your garage it is much cheaper to run with regular 240 single phase. You get 99.9999% of the welding ability on single phase and the average welder will not know the difference between 1 and 3 phase feeding his machine.And unless you are in an obscure location there are no "2 phase" systems currently in use in almost all modern countries. 2 phase power has its phased seperated by 90 degrees, all single phase power in the US is split phase with its phases at 180 degrees.
Reply:This provides a good description of "why" three phase is more efficient.http://www.threephase.info/benefitsthreephasepower.htm
Reply:and my inverter welder uses what I think is technically 2 phase, L1 @ 120v, L2 @ 120v and a neutral
Reply:Thanks David, I think you answered my question. I have an industrial shop that is supplied with 575, 3Ø but I picked up a 220/240 volt single phase welder and wanted to know where the efficiency lies. As for 3Ø welders being less expensive, around here they are nasty expensive, old junk sells for $2k.I appreciate all the answers, I've learned something from all of them.
Reply:Originally Posted by jmtebbensThis provides a good description of "why" three phase is more efficient.http://www.threephase.info/benefitsthreephasepower.htm
Reply:I always heard you could just use a 3 phase motor as a converter. just excite 1 phase and it puts out power on all 3.any sort of converter will kill any efficiency gains. they are really only to use second hand equipment.
Reply:Digital phase converters are getting cheaper and will give you the cleanest converted power of anything. They are basically an inverter that puts out a 3 phase waveform. Size can be a problem but I have seen them running up 15hp motors
Reply:Tagged (for link)http://www.threephase.info/benefitsthreephasepower.htm"Where's Stick man????????" - 7A749"SHHHHHH!! I sent him over to snag that MIC-4 while tbone wasn't looking!" - duaneb55"I have bought a few of Tbone's things unlike Stick-Man who helps himself" - TozziWelding"Stick-man"
Reply:3 phases of current as such ensures "a more stable" supply.When it comes to electric motors, 3 phase usually implies a more robust/industrialmotor and possibly lower rpms/noise. For the welder, 3 phase wouldlimit where you could use it but for "stationary" high power equipment,I would always recommend 3 phase.
Reply:I would like to clear up a couple things on this post. First 2 phase power is not all that uncommon. It is used mainly in rural areas to run farm motors (irrigation pump motors, grain elevators etc.) 2 phase does supply 3 phase power to the customer although Open Delta banks are not as efficient. 3 phase is what is generated and distributed and the phases are at 120 deg apart. Single phase is what feeds your house. 2 120 legs and a neutral from a single phase transformer. You can run a phase converter for welders but it takes a large generator approximately 25 or so hp to handle the load of most welders. I built one that is 8 hp that is capable of testing welders but I wouldn't weld too long. You would never want to run an inverter drive to run a welder. They are designed to run motors and provide a pulsed dc output to mimic an ac sine wave but have adjustable frequency for motor speed control.You cannot use a dc drive to make a phase converter simply because yoou need 2 legs of real ac to generate thethird leg and two of the line legs are also the load legs if that makes sense. wow that was long.HammerFile Big Hammer------------------------------Here, let me Google that for you...
Reply:Originally Posted by laverne3caCan someone explain why I've been told that 3 phase welders are better than 2 phase (some people call it single phase)? I can sort of understand the idea for a regular old style transformer type welder and the diode bridge but within the voltage limits of 2 phase supplies and with inverter technology, is there any real difference? After being 'processed' by the electronics in an inverter machine the output should be the same so where is the difference or is there one? Is it that the 3 phase supply is more efficient and therefore more cost effective?
Reply:I'm not sure the consensus is accurate.  Here is the spec from the Miller XMT304 CC/CV, A very common Inverter welder in industry:This shows that you get more power from a 3phase setup.  This was consistent with my previous Thermal Arc Inverter Welder.  More power is available from 3phase than 1 phase, even at the same voltage, it seems. Attached Images-DaveXMT304 with: 22A Feeder, or HF251 Hi Freq DC TIG air cooled
Reply:That is efficiency!  Exactly the point, three phase is more efficient = more power.
Reply:In the above example, the efficiency in single phase is very slightly higher.But with three phase, the available welding power will be significantly more.Single phase:Input power 7.6Kw, output power 6.525Kw (29v x 225A) efficiency 85.85%Three PhaseInput power 11.6Kw, output power 9.6Kw (32v x 300A) efficiency 82.75%This is not really surprising, because the exact same inverter is used in both.But the three phase unit has a higher dc input voltage available to that inverter, so it is able to work quite a bit harder, almost 47% harder.Cheers,  Tony._________________________________Transmig 310 + Argoshield LightOxy acetyleneOxy propanePrehistoric stick welder_________________________________
Reply:Originally Posted by laverne3caMy shop is supplied with 575 vac, 3 phase, and my inverter welder uses what I think is technically 2 phase, L1 @ 120v, L2 @ 120v and a neutral from the utilities transformer that supplies lights etc. so that across L1 and L2 there is 240 vac and yes, the power bill here is less than at home but I only wish the industrial power was that much less expensive here. I recognize that you generally can't get more than 240 volts as 'single' phase and I more or less understand the losses in transformers so my question really is, is the a three phase welder inherently more efficient or is it just the power supply?
Reply:Yes, if there is only L1 and L2 that is always single phase, either 110v or 220v is still single phase.Three phases always have L1, L2, and L3 with equal voltages between all three.Cheers,  Tony._________________________________Transmig 310 + Argoshield LightOxy acetyleneOxy propanePrehistoric stick welder_________________________________
Reply:In davec's example above, the efficiency (in watts) is similar but the power factor (the ratio of input KW to input KVA) is much better for 3-phase. This is because older inverter designs simply rectify and filter the single-phase power, which gives a low power factor.Newer inverters (e.g. the Miller XMT350 or the Lincoln C300) have what is called "active power-factor correction" which allows near-unity power factor on single-phase power. This circuitry also allows these machines to run on a wide range of input voltages without changing jumpers, a major advertizing point for the mfrs.However, no matter how efficient a welder might be, it will always draw less current on 3 phase than on single-phase power.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Originally Posted by jmtebbensThis provides a good description of "why" three phase is more efficient.http://www.threephase.info/benefitsthreephasepower.htm
Reply:one method of 'smoothing out' your power when using a phase converter is to run it through a 1:1 transformer. another method i've used is toput a cap bank between 2 legs, IIRC the caps are wired in parallel, at a rate of 1 mfd/ motor amp.someone please correct me if this is wrong.I only drink when I'm by myself or with somebodymiller deltaweld 452 w/s62 and xr-wmiller trailblazer 302lincoln dc400 w/ln7eutectic tig rig hypertherm 900lincoln stt II w/ln742Originally Posted by laverne3ca After being 'processed' by the electronics in an inverter machine the output should be the same so where is the difference or is there one?