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Phase converter for a shear

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  • Phase converter for a shear

    I'm stuck with single phase 220 and am in the process of buying a hydraulic shear that has a 20 HP motor on it, What size phase converter do I need.

    I've talked to a few people and I'm being told that I need to go 1-1/2 times the size of the motor so I will need a 30Hp phase converter.

    Is anyone running a shear or press brake off a phase converter.

  • #2


    • #3
      For a single machine, wouldn't it be easier and cheaper to simply change the motor? Since you are still buying single-phase power, only advantage to a phase converter I can see is the ability to buy other 3-phase equipment, and run them off the same phase converter.


      • #4
        I've never seen a single phase motor bigger than 7.5 Hp so let me go and see.


        • #5
          Isn't your overhead crane 3 phase? Or didn't that come about.


          • #6
            Variable frequency drives

            In addition to the rotating converters, which I think you are referencing, there is an electronic alternative. Some Variable Frequency Drive units have the ability to change single phase to three phase. I think that would be a less expensive solution. With a VFD you can also incorporate soft starts, etc. You would have to do some research, and change some of the controls, but this is another approach. You don't need the variable frequency, but the unit would do what you want, just leave the frequency at 60 hz.

            There are companies that you could call and have them help you size a VFD.

            With today's electronics, I would sure look at an electronic alternative. But if you can get a 30 hp motor cheap that might be the way to go.

            20HP is a large motor, of course, so would need an appropriately sized rotary converter or VFD.

            Note that 20 HP at 240 volts is around 70 amps, and that does not include the start-up current, which could be 4 times the steady state current or more. Do you have 400 amp service to your shop?

            Last edited by raferguson; 03-01-2013, 05:36 PM.


            • #7
              Raferguson, I might be in trouble, I only have a 200 amp service thanks for the advise.

              JS fab, A problem with the single phase motor is that this machine has a powered back gage, I'm not sure if they are hydraulic or electric motors that operate that and single phase motors dont normally spin both ways like a 3 phase motor does.

              MMW. I'm working on the 4 bridge beams this week end, my end trucks are done,
              I'm starting on the 4 bridge beams this week end and my ( 4 ) 2 ton hoists were ordered yesterday. By the time I bought the festoon cable trolleys ( 64 ) of them, the chain container and because my beam is 6.75" wide I had an up charge for a wider trolley I spent a little over $ 3,000.00 per hoist.

              To answer your question no my hoists are single phase. I bought Harrington hoists which is what I have in the front shop and they have been working good for the last 6 years.


              • #8
                Broccoli 1, Ya I looked at that site also, I left a message with the accurpress and still awaiting their call back.


                • #9
                  It may pay to build your own rotary phase converter as a VFD in the 20hp range for severe service like a punch press, shear or ironworker needs is going to run in the minimum of $4000 range. Even the rotary set-up is going to be devastating unless you have a cheap source for the 3-phase motor. The one good aspect of a VFD for your set-up would be it's ability to minimize the motor start-up inrush through the soft start feature. A large rotary converter could be started off a smaller pony motor to aleviate the initial amp draw demand. Best of luck.


                  • #10
                    Wont help but 10 hp single phase motors are available.


                    • #11
                      I use 20 H.P from to run a lathe with 20 H.P. and haven't had a problem. The company helped to size also.
                      The price was not as bad as that earlier post.


                      • #12
                        Originally posted by Lund Machine Works View Post
                        I use 20 H.P from to run a lathe with 20 H.P. and haven't had a problem. The company helped to size also.
                        The price was not as bad as that earlier post.
                        Excellent prices!!


                        • #13
                          Given your electrical entrance limitations have you considered using or converting your electric/hydraulic power pack to gas or diesel? Bit of a pain to have to start it up to work but much better than a hand pump. Might also consider a PTO drive from a tractor if that sort of thing is available close by or direct coupled to the tractor hydraulics if they are sufficient. Also reversible single phase electric motors are readily available.
                          Last edited by Meltedmetal; 03-02-2013, 05:51 AM.


                          • #14
                            Wyo Roy, I built my own before out of a Y- wound 3 phase motor so I kinda know how to do it, I used a little 115v motor with a vee belt pulley to get a 7-1/2hp motor going and then would energize the 3 phase motor and unplug the 115v motor. But that was a pain in the butt.
                            The professional ones use what they call caps to get the 3 phase motor going which is a little out of my league.

                            Lund, Thanks for the site, I will have to check their price. They offer a rotary and an electronic one ( Not sure which one would be best for my application.

                            Melted metal, I have to belive that I could start a 30 hp phase converter and the machine on less than 100 amps. but thanks for the ideas.


                            • #15
                              Originally posted by Portable Welder View Post

                              Melted metal, I have to belive that I could start a 30 hp phase converter and the machine on less than 100 amps. but thanks for the ideas.

                              I hope your faith is very, very powerful to get that 30 hp phase converter started...


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