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VFD for lathe

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  • VFD for lathe

    I want to install a VFD on my lathe. I have a 220/440v 2hp 3 phase motor and recently picked up this drive at an estate auction. First, is this a practical unit to use for this application? Input will be 220v single phase. From what I see per the instructions it is already wired for that. There is a jumper for hp, and I have reset that for 2hp. Second, is there anything I should know or do before powering it up?

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  • #2
    Looks good to me.
    21" Royersford Excelsior CamelBack Drillpress Restoration
    1943 Sidney 16x54 Lathe Restoration

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    • #3
      That’s not quite what I was expecting to see when I clicked on this thread.

      It looks like a nice unit to power a machine with.

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      • #4
        I's very close for 2 HP. Likely enough for most motors, maybe not enough for some. UL gives 6.8A for 2 HP, although their ratings do tend to be high. The 7.6A is higher, although not by the sort of margin I prefer.
        CNC machines only go through the motions.

        Ideas expressed may be mine, or from anyone else in the universe.
        Not responsible for clerical errors. Or those made by lay people either.
        Number formats and units may be chosen at random depending on what day it is.
        I reserve the right to use a number system with any integer base without prior notice.
        Generalizations are understood to be "often" true, but not true in every case.

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        • #5
          Originally posted by Stu View Post
          Second, is there anything I should know or do before powering it up?
          What has been mentioned many times on this forum, is that the big capacitors don't necessarily age well. It has been suggested that the voltage be brought up in steps. Do you have a variac, by chance?
          The experts here can elaborate better than I am able, should this be applicable.
          Location: North Central Texas

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          • #6
            Watch for cap smoke when you power it up the first time.

            Electrolytics will be dried out after a couple of decades, especially if it's sat without power for a long time.

            You can probably find replacements, however big "lytics of a high voltage rating are one of the main BOM cost drivers in a VFD I'd reckon.
            -paul

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            • #7
              If it were mine....

              I would set it up as you have described, and energize it with 110V, Just the VFD, Not connected to any motor at all.

              See if the display and controls all appear to function as expected. Leave it powered up for a day. Reforming the capacitors.

              Then I would connect it to 220V and again check things out and leave it connected for a day.

              Then I would connect the unit to a fractional HP 3ph motor (if available) or connect it to the motor you have, but don't put a mechanical load on it.

              Run the motor, play with speeds / accel /decel times etc. Make sure all the "features work, and the control wiring is the way you want it and needs to be.

              All "bench work".

              Run the motor for a few hours. play with frequencies between 15hz and 75 hz Does it growl at some frequency? Make a note!

              If all is well, Hook it up to load, and see if the unit over current faults on rapid accel / decel. adjust times to suit.

              Good to go!

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              • #8
                Originally posted by CalM View Post
                If it were mine....

                I would set it up as you have described, and energize it with 110V, Just the VFD, Not connected to any motor at all.

                See if the display and controls all appear to function as expected. Leave it powered up for a day. Reforming the capacitors.

                Then I would connect it to 220V and again check things out and leave it connected for a day.

                Then I would connect the unit to a fractional HP 3ph motor (if available) or connect it to the motor you have, but don't put a mechanical load on it.

                Run the motor, play with speeds / accel /decel times etc. Make sure all the "features work, and the control wiring is the way you want it and needs to be.

                All "bench work".

                Run the motor for a few hours. play with frequencies between 15hz and 75 hz Does it growl at some frequency? Make a note!

                If all is well, Hook it up to load, and see if the unit over current faults on rapid accel / decel. adjust times to suit.

                Good to go!
                Thanks, exactly what I was looking for, I got it for less than 20$ so it's no big lose if it does go up in smoke. Stu

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                • #9
                  Looks like a good idea, but just having motor control is no complete substitute for mechanical speed changing. I have one for the Tom Senior mill which I converted from MT2 to R8 spindle and from a 1/2hp single phase to a 1hp three phase with a VFD. The motor which is 6 pole runs from 1/2 to 1 1/2 basic rpm, but the 4 speed belt drive is still used for the slow speeds especially.
                  Be careful of reversing if the spindle is threaded without some form of lock, except at very slow speeds.
                  Also make sure of the requirements, star or delta motor connections that match the inverter.
                  Last edited by old mart; 05-31-2022, 01:22 PM.

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                  • #10
                    Originally posted by Stu View Post

                    Thanks, exactly what I was looking for, I got it for less than 20$ so it's no big lose if it does go up in smoke. Stu
                    So you got it cheap, so you are going to be careless with it?
                    Does low price equate to low value ?
                    I hope your logic serves you well in life.

                    -D
                    DZER

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                    • #11
                      Here's my story. Professionally retrofitted CNC lathe.

                      2hp spindle motor, nominal 1800 rpm. Yaskawa VFD rated to 5 hp with 230V single phase input.

                      Worked fine on smallish parts which was its intended function. Then I got an ongoing big job hogging lots of material off 5" aluminum rounds. The machine bogged down when I needed the rpm to break chips at the major diameter. I changed the motor to one with 3 hp, nominal 1200 rpm. Made all the difference in the world.

                      Another VFD oddity.... I bought a new Teco brand 1hp capacity VFD, 120V single phase input.. It runs some 1 hp motors and not others. In this case I attribute the problem to the VFD rating too close to the motor's hp.

                      Another VFD story.... This one was an old Parametrics Variable Speed Drive (I guess before the term "VFD" came into use). Rated for 2 hp motors with 230V single phase input. I bought it at a scrap yard for the case it was in. I decided to give it a try. it worked like a charm. Then I sold the machine it was used on. The unit sat unused for at least 5 years. Sold it to a friend and it wouldn't work. Probably bad caps as others mentioned.

                      I had the same situation with a factory made rotary phase converter. Got a killer deal at an auction. It worked fine initially. Then it was in my storage area for close to ten years and it wouldn't work after that.

                      A RPC story. Bought a new locally made 10 hp converter, company had been in the business for a number of years. 10 years into my use I was running my CNC mill on it. I heard a load noise like a piece of metal falling to the concrete floor. Didn't think too much of that, just vibration knocking something off the shelf. Then I happened to glance at the RPC and the enclosure burst into flames with fire coming out of all the enclosure's seams. Quickly shut off power. The fire went out. A capacitor had exploded. 20 mile drive to the manufacturer, 50 bucks to install a new one and I was good to go again in 4 hours.

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                      • #12
                        Originally posted by Doozer View Post

                        So you got it cheap, so you are going to be careless with it?
                        Does low price equate to low value ?
                        I hope your logic serves you well in life.

                        -D
                        I don't think that's my logic, but then again I don't know myself as well as you do. I have to ask, where in my statement did you get the idea I was going to be careless. Stu

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                        • #13
                          Old caps on something like that are likely to need the current applied slowly.
                          Think a variac or at least a 60w lightbulb in series to limit the current.
                          Else having them explode is a real possibility.

                          I have two 10hp VFDs that I have had in storage for 12 years.
                          I absolutely will use a variac and a light bulb to slowly apply the current
                          for the first time.

                          Caps that blow up sound like a good sized fire cracker.

                          -D
                          DZER

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                          • #14
                            Originally posted by Doozer View Post
                            Old caps on something like that are likely to need the current applied slowly.
                            Think a variac or at least a 60w lightbulb in series to limit the current.
                            Else having them explode is a real possibility.

                            I have two 10hp VFDs that I have had in storage for 12 years.
                            I absolutely will use a variac and a light bulb to slowly apply the current
                            for the first time.

                            Caps that blow up sound like a good sized fire cracker.

                            -D
                            Thanks, I'll try that. Stu

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