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Powering 5.5KW (7.5hp) lathe with clutch

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  • Powering 5.5KW (7.5hp) lathe with clutch

    First of all, I'm no sparky so go easy... I've been trying to determine how to power this thing with minimal expense. I have another lathe that does most of what I need. This one would see only occasional use when I need the larger size.

    I just acquired a 1960s vintage lathe with a 5.5kw 3 phase drive motor. Currently wired 440. Motor says 220/440 on the tag. I have plenty of 240 single phase available.

    I have a 5hp idler motor and static converter on hand. Do you think I could start this lathe with a 5hp 3 phase idler and a static converter? I cannot imagine needing the full 5.5kw of the lathe motor. Possibly need to adjust something with the motor starter or overload heaters, not sure. I'm content to have less power available as long as I can start it.

    I have wired up VFDs and feel comfortable with that but I really don't want to risk a cheap vfd. Automation Direct I'm looking at $1000+ for a vfd. Ouch.

    A commercial rotary converter and step up transformer would do this job with zero modifications I believe. But that's going to cost $1000+ too.

    I really don't want to swap motors in the lathe but that is a possibility.

    Looking for suggestions! What would you do?


  • #2
    The cheaper type converters, i think one uses diodes.. are less effecient.. you lose a bit of power..
    but i think 2 to 300ish range.. if you have a KBC catalog, might be info in there..

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    • #3
      If your motor is wired for 230v, then you have paralleled windings. Be it Y or Delta.
      Open up one set of windings and start the motor on half the windings.
      This should allow for lower current starting.
      If I am wrong, maybe Jerry can comment, but it seems workable to me.

      -D
      DZER

      Comment


      • #4
        Dude it's clutch lathe. They start almost as easy a plain motor. You could start it with a 7.5 HP static box. Or yours with an additional cap hanging out the side. Add in the idler and some run caps if you want full power.

        Doozer you know, the same way your P&W came. Stroker should just emulate that setup.
        21" Royersford Excelsior CamelBack Drillpress Restoration
        1943 Sidney 16x54 Lathe Restoration

        Comment


        • #5
          Hmmmm. Sounds like I might be able to make this work with the static converter I already have with or without the 5hp idler. Just need to wind up the motor, four vee belts, and the headstock input shaft. Full power is not needed.

          I need to do some more investigating on the controls. Starter contactor, etc.

          I will post back with what I find and probably another question or two.

          Thanks for the suggestions!

          Comment


          • #6
            Honestly I feel like this is one of the rare situations that is appropriate for a static box. I hate the term "converters," because after all, what are they really but start caps and a potential relay. But on a clutch lathe you're idle any time that you're stopped, and there is very little starting torque required. So it's really well suited.

            If you wanted to you could do a very clean installation by putting it in the electronics cabinet (if there is room). If you start switch is a dual pole, you could use it to fire the relay, but probably better to use the potential relay if it's a reversing machine. I'm not too educated on that so I'll let others guide there.

            PS, on the motor, if all 9 wires come up to the control panel and are labeled you can re-wire it there. If not, you'll have to get into the motor peckerhead and rewire it there. So long as you have 9 wires you're good and don't need (or want) any transformer. You will need to swap your overload heaters or they will trip very prematurely.

            I would try your 5hp static box as is to see if it works. You might be fine. Check your wiring to make sure that all the controls are on the real legs and not getting buzzed by the cap. If it fails to start it or starts it slow, one additional start cap may be enough.

            Lastly if you just want to try the machine out, you could spin it up with a big drill or something and a rubber contact wheel before hitting the button.
            21" Royersford Excelsior CamelBack Drillpress Restoration
            1943 Sidney 16x54 Lathe Restoration

            Comment


            • #7
              You might be able to get a big 10 HP or larger 440 VAC VFD for cheap, under $100. Then you just have to get a step-up autotransformer for 220 to 440 VAC. A 3 kW 220-220 isolation transformer can provide 6 kW when wired as an autotransformer, and such units are often available for maybe $200 or so.

              https://www.ebay.com/itm/18462674991...UAAOSwnR9gBbaE

              https://www.ebay.com/itm/13339746511...IAAOSw9EteqHoD

              https://www.ebay.com/itm/13347728846...gAAOSwwvtfIF4e

              http://pauleschoen.com/pix/PM08_P76_P54.png
              Paul , P S Technology, Inc. and MrTibbs
              USA Maryland 21030

              Comment


              • #8
                Don’t rule out a 1ph motor if you have a 3 or 5hp laying around,I’ve been running a 18x60 with 5hp that was equipped with 10hp 3ph.Mine is clutchless style so motor runs fwd & reverse.

                Comment


                • #9
                  Stroker6,
                  Use a VFD, give me a call, you have my #. Just did this in my shop. Tom

                  Comment


                  • #10
                    If I understand the post title correctly this lathe has a spindle starting clutch, so the motor runs continuous while the lathe is in operation. Sense this is not your primary go-to workhorse machine you should be fine running off a static phase converter with its inherent power loss.

                    Comment


                    • #11
                      I am inclined to agree with the idea of using the "static start box". It's simple, far simpler than the VFD or RPC, each of which has cost and/or demands for rewiring of controls.

                      Yes, being a clutch type machine really makes the case for it, as you will never have to start it loaded. OK, it might depend slightly on exactly where the clutch is..... if it is in the headstock, the motor will have to start a certain amount of moving mass, but the static box will do that (if of the right size for the motor). If down with the motor, before the pulleys etc, then the motor will start essentially totally unloaded.

                      It only has to start once per session, and never into a load.

                      It really is the best case for a static box, assuming you have no need for sustained operation at higher than 50 to 60% of power. And it is your cheapest way in for a machine that is not the primary lathe.
                      4357 2773 5647 3671 3645 0087 1276

                      CNC machines only go through the motions

                      "There's no pleasing these serpents"......Lewis Carroll

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                      • #12
                        Originally posted by PStechPaul View Post
                        You might be able to get a big 10 HP or larger 440 VAC VFD for cheap, under $100. Then you just have to get a step-up autotransformer for 220 to 440 VAC. A 3 kW 220-220 isolation transformer can provide 6 kW when wired as an autotransformer, and such units are often available for maybe $200 or so.

                        https://www.ebay.com/itm/18462674991...UAAOSwnR9gBbaE

                        https://www.ebay.com/itm/13339746511...IAAOSw9EteqHoD

                        https://www.ebay.com/itm/13347728846...gAAOSwwvtfIF4e
                        Confused an curious Paul. Why recommend a transformer when he has a dual voltage lathe? They were meant to be set to the operators voltage. All that needs to be done is the following:
                        1. Open the motor peckerhead and rewire. Should be a diagram. If not, as long as the wires are labeled an internet diagram will help. If not still... there are ways. Steve Watkins on youtube has a video.
                        2. Change the controls transformer for the new input voltage. Again, should be a diagram.
                        3. Look up the appropriate heaters and buy and install them.
                        Even at a leisurely pace that's a 1/2 hour of work and nearly free. Unless his motor was been chopped and modified or there is no reason that can't be a 240V lathe.
                        21" Royersford Excelsior CamelBack Drillpress Restoration
                        1943 Sidney 16x54 Lathe Restoration

                        Comment


                        • #13
                          There are two reasons for what I proposed. First, 440 VAC VFDs for high power are very inexpensive on the used market. I bought a 5 kW 7.5 HP Toshiba VFD for something like $85, and I was given a couple others of similar HP by a member of HSM. Adding a transformer to get 480 VAC from a 240 VAC supply is also inexpensive, especially if you can find a transformer locally to minimize shipping cost.

                          The second reason for using a 440 VAC VFD is that it is possible to use a 240 VAC 1750 RPM 5 HP motor on 480 VAC 120 Hz to get 10 HP at 3500 RPM.
                          http://pauleschoen.com/pix/PM08_P76_P54.png
                          Paul , P S Technology, Inc. and MrTibbs
                          USA Maryland 21030

                          Comment


                          • #14
                            Originally posted by PStechPaul View Post
                            There are two reasons for what I proposed. First, 440 VAC VFDs for high power are very inexpensive on the used market. I bought a 5 kW 7.5 HP Toshiba VFD for something like $85, and I was given a couple others of similar HP by a member of HSM. Adding a transformer to get 480 VAC from a 240 VAC supply is also inexpensive, especially if you can find a transformer locally to minimize shipping cost.

                            The second reason for using a 440 VAC VFD is that it is possible to use a 240 VAC 1750 RPM 5 HP motor on 480 VAC 120 Hz to get 10 HP at 3500 RPM.
                            It doesn't need a VFD.... like... at all. That's just throwing bad money after good.

                            Second... 15HP at 3500 RPM is the last thing he is gonna want. It would probably be pouring oil out of every joint and crevice due to the pump running at twice the speed. And probably screaming. What he needs is a couple caps at min, an RPC at most.
                            21" Royersford Excelsior CamelBack Drillpress Restoration
                            1943 Sidney 16x54 Lathe Restoration

                            Comment


                            • #15
                              Motor data plate on this lathe: Anything jump out as a problem? I'm curious why the amp rating isn't exactly half for 440v. Also noted 1165 rpm.Click image for larger version  Name:	motor plate.jpg Views:	0 Size:	1.19 MB ID:	1943890
                              Last edited by strokersix; 05-22-2021, 10:59 AM.

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