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Variable speed AC Drive

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  • Variable speed AC Drive

    Has anyone experience with using these new type AC variable speed controllers with 3 phase motors for drives on lathes. I see new controllers and motors in the 1/2-3/4hp range that come with prices under $300.00. The controllers I have seen can do constant torque variable speed and do forward and reverse as well! How well do these work with respect to the DC units?


  • #2
    I have one on a 3hp colchester & love it... nice to be able to fine tune speed, instant stop for threading, etc


    • #3
      My company makes hundreds of thousands of them every year. For running a lathe spindle, you really can't beat them for price, power efficiency, features, and maintenance. Unless of course you can get an old DC system for free, then it would win on price.


      • #4
        I haven't heard of anything new. How are they different from a VFD?
        Southwest Utah


        • #5
          You may want to try using the search function. There is a lot of previously posted information on this subject.


          • #6
            Could someone tell me the difference between an AC variable speed controller & a VFD?
            I have 2 VFD's and love them.


            • #7
              It's the same thing just different names......

              There are different types, they do the same thing, but vary in the bells and whistles, like "vector control" vs "V/Hz", etc.

              Those things can be important, but in general, they all output a variable frequency, which in turn makes a 3 phase AC induction motor into a variable speed motor. The details are in exactly HOW they do that.

              You can get a 1 HP VFD from Dealer's Electric for as little as $120. That one is a TB Woods (made by Invertek in UK). They have TECO, and others as well.
              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.


              • #8
                Define these? It's a huge subject. A link to an example might help you get useful input.


                Originally posted by skipd1
                ..... these new type AC variable speed controllers with 3 phase motors for drives on lathes.


                • #9
                  afaik they are just a VFD, some are more sophisticated than others, but unless you have a specific need for the advanced features why spend the extra


                  • #10
                    Originally posted by philbur
                    Define these? It's a huge subject. A link to an example might help you get useful input.

                    If he is referencing them to DC drives, any VFD (Variable Frequency Drive, aka AC variable speed control) is one of the new ones.


                    • #11
                      A VFD can be set-up to mimic a DC drive such that you would have an extremely difficult time telling the difference between the two, with the exception of the VFD's carrier frequency. On mine it seems to occur in a limited range.

                      I have 2 Monarch 10 EE's, one with a Sensorless Vector Drive, and one with original DC drive. Both machines are 5 HP drives. The VFD has external braking resistors added, as the internal braking couldn't do the job. My baseline is stopping the spindle with a 6" 3 jaw Set-Tru chuck from 1500 RPM is less than 2 seconds. The VFD does this in about 1.5 seconds, the time is adjustable, but I was afraid of tripping the overloads with a faster stop. The DC machine with a 5-C collet set-up stops in about 2 seconds, and stop time is not adjustable.

                      As far as low end torque is concerned, the DC drive may have the advantage under 150-250 RPM in direct drive, but I do have backgear on both machines, so it is a non-issue with me.

                      If the DC drive ever has major issues a VFD will replace it, no questions asked.