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    VFD Newbie questions

    Have a 3-phase, 208 v, 3 HP motor.

    It is currently setup with typical motor starter/fused disconnect with forward/reverse contacts and thermal OL's.
    A direction selector switch (non-latching) is located on the side of the unit.

    The customer wants to set it up with a VFD to control the speed, minimize the sudden jerk of starting and stopping.

    I don't have first-hand experience. I understand how VFD's work, but have questions about getting it setup to do what the customer wants.

    I plan to leave the existing motor starter box where it's located and mount the VFD in an adjacent box with a nipple between the 2 enclosures.

    -I'm assuming that I'll by-pass the existing contactors and re-route the conductors (load side of fuses at disconnect). Does a typical VFD perform OL functions, or do I have to continue to use the existing OL's?

    -they want controls mounted to the side of the enclosure that will allow the operator to choose the direction (forward/reverse) of motor and the speed.
    My understanding is that the speed is controlled by some sort of potentiometer, typically does each manufacturer provide a potentiometer for their VFD or are there "universal" potentiometers that I should look at choosing?

    -how does the operator select the motor direction? I.e., what sort of button setup should I be looking for?

    -I'm sure the customer will want a display of some sort that shows which direction is selected before using the potentiometer to operate the button.

    These are all fairly basic functions, I know how to do this with your typical motor starter setup. I just don't have experience with VFD's.

    Thanks for any basic info/answers!

    #2
    Go online and download an installation manual for a VFD. Read it. Then go for the operators manual. Pick a basic VFD like an AB PowerFlex 4, or AD GS2 or 3.

    Leave the more complicated and higher end ones alone. You don’t need the confusion at this stage. Nobody doese.

    eta: https://literature.rockwellautomatio...m001_-en-e.pdf
    Tom
    TBLO

    Comment


      #3
      FWIW

      We always had a contactor on the output side of the VFD. For safety reasons, we had to have a physical disconnection means But we had a shutdown sequence that ensured that the VFD was shut off before the contactor was opened.
      Reversing?
      Normally available via the keypad but you can very likely use an external relay into a VSD input if you needed to do it from a remote rather than local position.

      Comment


        #4
        Originally posted by ptonsparky View Post
        Go online and download an installation manual for a VFD. Read it. Then go for the operators manual. Pick a basic VFD like an AB PowerFlex 4, or AD GS2 or 3.

        Leave the more complicated and higher end ones alone. You don’t need the confusion at this stage. Nobody doese.

        eta: https://literature.rockwellautomatio...m001_-en-e.pdf
        The customer has a referral to a Mitsubishi VFD that is used for this application in other locations similar to this one. I have already downloaded the manual and am reading through it.

        My local supply house carries AB. I have a call in to them to get info on a comparable AB version.

        Any thoughts about AB vs Mitsubishi? The only reason I was looking at AB is tech support from the supply house regarding peripheral items, like the enclosure and potentiometer, etc. but maybe I'm overthinking things...

        Comment


          #5
          Originally posted by sw_ross View Post
          The customer has a referral to a Mitsubishi VFD that is used for this application in other locations similar to this one. I have already downloaded the manual and am reading through it.

          My local supply house carries AB. I have a call in to them to get info on a comparable AB version.

          Any thoughts about AB vs Mitsubishi? The only reason I was looking at AB is tech support from the supply house regarding peripheral items, like the enclosure and potentiometer, etc. but maybe I'm overthinking things...
          I try to use what is available locally if I feel I need an immediate replacement or help (AB). I don't remember working on a Mitsubishi, so I can't compare. Do you have a supplier of Mitsubishi in State?
          Tom
          TBLO

          Comment


            #6
            If you get a unit with interface keypad/display you generally can stop, start, change direction, monitor output, etc all from that interface unit as well as change operating parameters with it. Usually set up for keypad control as default, but you can change settings to allow remote devices to control it. External potentiometer for external speed control - usually requires either a 5k or 10k 3 wire pot. Other speed control options may be 4-20 mA or 0-10 V input by some other analog device and works great if automatic speed control is necessary for an application. Then there is usually other digital communications abilities for control by PLC's or other digital items., just need to know how to set parameters and use these features, but simple start, stop, FWD,REV and three wire speed pot are pretty common on simpler installations, and so is just using keypad on the unit in some instances.

            Many of those units even are capable of remote location of the keypad if you don't want the drive located right at the operator station but still want to use the keypad for contol.
            I live for today, I'm just a day behind.

            Comment


              #7
              Originally posted by ptonsparky View Post
              I try to use what is available locally if I feel I need an immediate replacement or help (AB). I don't remember working on a Mitsubishi, so I can't compare. Do you have a supplier of Mitsubishi in State?
              My customers referral is to the website VFDs.com
              I'm not sure if the link was sent to them (referral) or if they googled the VFD that was referred to them.

              Maybe I'll contact the tech support and see how helpful they are regarding the installation...

              Comment


                #8
                They are not that hard to install and it sounds like you have a very basic operation.

                You may want to meg your motor and conductors to it, before applying a VFD. It will find problems you didn't know you had and of course, you will be blamed.
                Cooling of the motor via its fan will be reduced as the rpm is reduced, so continued operation at low speeds can be a problem. A minimum speed can be set.
                Newer motors are more likely to have better insulation rated for use with VFDs and in that context, try to limit your distance to the motor as indicated in the manual.
                Line reactors are a good idea, as are load reactors for older motors and/or the distance to it is excessive.

                In short again, read the manual.
                You will be fine.
                Tom
                TBLO

                Comment


                  #9
                  Originally posted by ptonsparky View Post
                  They are not that hard to install and it sounds like you have a very basic operation.

                  You may want to meg your motor and conductors to it, before applying a VFD. It will find problems you didn't know you had and of course, you will be blamed.
                  Cooling of the motor via its fan will be reduced as the rpm is reduced, so continued operation at low speeds can be a problem. A minimum speed can be set.

                  When driving a variable torque load such as a fan or pump, this may not be a problem. constant torque loads cooling of the motor can be a problem at lower speeds. Externally powered cooling fans sometimes is necessary.

                  Newer motors are more likely to have better insulation rated for use with VFDs and in that context, try to limit your distance to the motor as indicated in the manual.
                  Line reactors are a good idea, as are load reactors for older motors and/or the distance to it is excessive.

                  That insulation rating of motor is usually more critical on older motors (that are not using same magnet wire as newer motors usually have) if operating at 480 volts as the base 60 Hz volts. If running a dual voltage motor on 208-240 volts you simply won't stress the insulation on same windings with the voltage spikes seen at the low voltage as you will at the high voltage. 480 volt drive output can see voltage peaks that are over 800 volts and that tends to be a problem for the winding insulation, is worsened by long circuit runs from the drive to the motor.

                  In short again, read the manual.
                  You will be fine.
                  I'm not trying to educate you tom, I think you know most of what I said, just adding some content to what you said for possible benefit of OP.
                  I live for today, I'm just a day behind.

                  Comment


                    #10
                    Originally posted by kwired View Post
                    I'm not trying to educate you tom, I think you know most of what I said, just adding some content to what you said for possible benefit of OP.
                    I had already forgot he said 208v. Educate me. Someone has to. Over and Over and over. CRS!!
                    Tom
                    TBLO

                    Comment


                      #11
                      Thanks for the words of wisdom!...

                      Comment


                        #12
                        So I called the 1-800-# on the VFD's.com website to get some sort of tech support to ask questions about the Mitsubishi VFD.

                        The person tells me they don't have any tech support, but I can "schedule" tech support with Mitsubishi for a fee!...

                        I asked him about if a customer has an issue with their VFD, or other products, how is it dealt with.... He didn't have an answer.

                        Kinda crazy!

                        Comment


                          #13
                          Originally posted by sw_ross View Post
                          So I called the 1-800-# on the VFD's.com website to get some sort of tech support to ask questions about the Mitsubishi VFD.

                          The person tells me they don't have any tech support, but I can "schedule" tech support with Mitsubishi for a fee!...

                          I asked him about if a customer has an issue with their VFD, or other products, how is it dealt with.... He didn't have an answer.

                          Kinda crazy!
                          Sounds like AB just got a sale, or at least closer.
                          Tom
                          TBLO

                          Comment


                            #14
                            Originally posted by sw_ross View Post
                            Have a 3-phase, 208 v, 3 HP motor.

                            It is currently setup with typical motor starter/fused disconnect with forward/reverse contacts and thermal OL's.
                            A direction selector switch (non-latching) is located on the side of the unit.

                            The customer wants to set it up with a VFD to control the speed, minimize the sudden jerk of starting and stopping.

                            I don't have first-hand experience. I understand how VFD's work, but have questions about getting it setup to do what the customer wants.

                            I plan to leave the existing motor starter box where it's located and mount the VFD in an adjacent box with a nipple between the 2 enclosures.
                            Why leave the old box there? No reason for it any more.

                            -I'm assuming that I'll by-pass the existing contactors and re-route the conductors (load side of fuses at disconnect). Does a typical VFD perform OL functions, or do I have to continue to use the existing OL's?
                            Yes, the VFD will have OL protection for the motor, no need for the old OL heaters. Again, no need for the old starter at all.

                            -they want controls mounted to the side of the enclosure that will allow the operator to choose the direction (forward/reverse) of motor and the speed.
                            My understanding is that the speed is controlled by some sort of potentiometer, typically does each manufacturer provide a potentiometer for their VFD or are there "universal" potentiometers that I should look at choosing?
                            It would be any standard potentiometer, but the resistance value might be different from one brand to another. Most will want a 10kOhm pot, but some are 1kOhm, I've seen others that are looking for a 100kOhm. RTFM (Read The F***** Manual)

                            -how does the operator select the motor direction? I.e., what sort of button setup should I be looking for?
                            All you need is a selector switch that closes one contact to tell the VFD to run in reverse, the "normal" direction will be Forward. the drive will then swap a phase going to the motor electronically.

                            -I'm sure the customer will want a display of some sort that shows which direction is selected before using the potentiometer to operate the button.
                            Most VFDs come with a display (or option for a remote one).

                            These are all fairly basic functions, I know how to do this with your typical motor starter setup. I just don't have experience with VFD's.

                            Thanks for any basic info/answers!
                            If you have an AB distributor handy, I would do it with a PowerFlex 523 drive. Simple, robust, has a built-in potentiometer. Local support is the most important factor, especially for newbies.
                            __________________________________________________ ____________________________
                            Many people are shocked when they discover I am not a good electrician...

                            I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

                            Comment


                              #15
                              My experience

                              Originally posted by Jraef View Post
                              If you have an AB distributor handy, I would do it with a PowerFlex 523 drive. Simple, robust, has a built-in potentiometer. Local support is the most important factor, especially for newbies.
                              JR's summary is good.
                              Most of my setup experience is with ABB drives. The main thing I have found is the DOCs are horrible are seemingly not written by people who really understand field work. The manuals are like an encyclopedia, cryptic, and very non-intuitive. In working with Tech support, they have been helpful but there are scenarios where things will not work and it takes some persistence. Reading the manual is mind numbing and distasteful.
                              There have been at least 2 situations where Tech support either could not answer the problem or I had to figure it out on my own. The guys that have their hands in them every day must have an edge.
                              There are bypass stations if you need the redundancy to side step the drive. They are pricey.
                              Microwave Radiation Dangers should be openly discussed

                              Comment

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