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  • Yet another VDF question

    I am ready to wire up my new Griz G0519 to a Hitachi VFD. I have thoughly read the Hitachi manual..
    If I wire the VDF to the Griz control panel then I'll have to hit the Run sw on the VDF to power the mill controls. That means the VDF will be on with no load. WILL THIS HARM THE VDF????? I know some circuits don't like to be energized without a load attached.

    I am leaning toward removing the Griz control panel and wiring the VDF straight to the motor.
    Your comments please.
    Gary Davison
    Tarkio, Mo.

  • #2
    Hi Gary,

    It sounds like you've got it right -- no switches between the 220V line and the VFD, and use the Run/Stop controls on the VFD to turn the mill on and off. I've completely removed the control panel from my mill, but on my lathe I wired the switches on the headstock to the external switch inputs on the VFD. The Hitachi has this too.

    In other words, you can use the drum switch on the mill as remote switch for the VFD Run/Stop.

    Cheers,

    Robert
    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

    Comment


    • #3
      Originally posted by gld

      If I wire the VDF to the Griz control panel then I'll have to hit the Run sw on the VDF to power the mill controls. That means the VDF will be on with no load. WILL THIS HARM THE VDF????? I know some circuits don't like to be energized without a load attached.

      I am leaning toward removing the Griz control panel and wiring the VDF straight to the motor.
      Your comments please.
      DO NOT WIRE a VFD output to a motor switch. The momentary inrush of current to a stopped motor shaft will usually exceed the VFD capability. VFD's ramp up slowly (OK, maybe a second or two) to prevent overcurrent problems. No, it won't harm the VFD, it'll just issue an error code and shut off.

      No problem having a disconnect on the input, if you use it when the motor is turned off.

      Best to rewire the whole thing, easier in my mind. I used the Griz contactors to close the 5V VFD inputs for direction on my 4003.

      Dave

      Comment


      • #4
        Originally posted by lazlo
        Hi Gary,

        It sounds like you've got it right -- no switches between the 220V line and the VFD, and use the Run/Stop controls on the VFD to turn the mill on and off. I've completely removed the control panel from my mill, but on my lathe I wired the switches on the headstock to the external switch inputs on the VFD. The Hitachi has this too.

        In other words, you can use the drum switch on the mill as remote switch for the VFD Run/Stop.

        Cheers,

        Robert
        Hmmm. Most of the wisdom I've gleaned says put a multipole switch near the tool between your breaker and VFD, and as others have said, NEVER put a switch between the VFD and the motor.

        Whether you can use the drum switch for the low V external control probably depends on the VFD firmware design. Neither my Toshiba nor Woods will do that. I have my drill press control panel to the Woods with a DPDT momentary center off switch for FW and REV, and a nice fat momentary N.C. OFF button that I can actually hit with my forehead in a pinch. But I was told by Toshiba that there's no way to do the same with their equipment for my mill, I would have to use a non-momentary Estop. So, they're all different,at least the 2 I have are very different in term of external control.
        Last edited by gellfex; 04-14-2008, 12:56 PM.
        Location: Jersey City NJ USA

        Comment


        • #5
          Originally posted by gld
          I am ready to wire up my new Griz G0519 to a Hitachi VFD. I have thoughly read the Hitachi manual..
          If I wire the VDF to the Griz control panel then I'll have to hit the Run sw on the VDF to power the mill controls. That means the VDF will be on with no load. WILL THIS HARM THE VDF????? I know some circuits don't like to be energized without a load attached.

          I am leaning toward removing the Griz control panel and wiring the VDF straight to the motor.
          Your comments please.
          I have an SJ200 Hitachi and, while the VFD is "energized" when the power is on, it sends nothing to the motor until you hit "Run" as you mentioned but not a problem at all with that.
          Still using the OE mill switch ( I was pleased to find the Chinese sourced German switches for this machine) but find it extremely convenient.
          Otherwise, no way to de-energize the VFD.
          Len

          Comment


          • #6
            Originally posted by gellfex
            Hmmm. Most of the wisdom I've gleaned says put a multipole switch near the tool between your breaker and VFD, and as others have said, NEVER put a switch between the VFD and the motor.
            Right, as I said, no switch between the VFD and the motor.

            If I'm reading his question correctly, the OP was asking if he could use the control switch on the Grizzly for the Run/Stop function on the VFD, which you can.

            I have an SJ200 Hitachi and, while the VFD is "energized" when the power is on, it sends nothing to the motor until you hit "Run" as you mentioned but not a problem at all with that.
            ...
            Still using the OE mill switch
            That how I have my VFD's -- always on (connected with line power), and using the OEM switch for a remote Run/Stop signal if convenient.

            I think the electrical code wants a shutoff switch between the VFD and line, but I just unplug the VFD if I'm not going to be using the machine for awhile.
            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

            Comment


            • #7
              Bump - because a new extended delivery date on a G0484 has me considering the G0519.

              Q - Other than turning the G0519 on and off from the VFD, why would you necessarily need to connect any controls from the G0159 to the VFD? The G0519 expects 3 phase power and is already set up with a reversing switch, etc to control the motor. Seems to me that the VFD has only two uses in this app - send 3 phase power to the mill and provide the option change the line freq as a method of controlling motor speed. You would not need the reverse capability or start/stop on the VFD. I must be missing something about how the VFD works in real life?
              Chris
              Merkel, Tx
              http://raceabilene.com/kelly/hotrod

              Comment


              • #8
                Falcon67, While you can control all motor functions from the VFD, it makes it more "natural" to use the machine if the original controls are used as logic inputs to the VFD, controlling the functions they used to do directly.

                On the Harrison M300 lathe, the forward/stop/reverse control is on the apron and an emergency foot switch is present. All of these controls happen to have switch contacts that originally worked thru relays to do their job. Now, I have them going to logic inputs on the VFD so they tell it what to do but IT actually performs the function (except for an e-stop which the Hitachi VFD doe not support directly).

                On a mill, you may have a forward/stop/reverse switch and the same applies. The switch goes to logic inputs on the VFD.

                If a machine has a power cutout switch, I would wire that to feed the INPUT side of the VFD, providing a way to cut all power if necessary.

                Just re-read your post and need to clarify ... the VFD output must go directly to the MOTOR in most cases. If you do otherwise, you risk damaging the transistors in the output stages of the VFD. Transients caused by contact switching can do damage. They are normally switched electronically (and transient free) under control of the microcontroller in the VFD. So ... any original switches should become control switches fed to the VFD logic level (low voltage) inputs.

                Den
                Last edited by nheng; 08-16-2009, 09:47 PM.

                Comment


                • #9
                  I have a Griz 0519 with a VFD. I used the switched that came with the machine, but did not use the contactor. In other words, I rewired the machine to be compatible with the VFD. I was also able to keep the tapping feature.

                  Comment


                  • #10
                    Thanks, that clears that up. Appreciate the help very much.

                    The only other issue I see is that you'd have to get a VFD for a 1.5 or 2 HP application - Griz lists the current draw of the G0519 motor at 4.5A, which is .5A over most of the VFDs I've looked at.

                    The due date on the 0159 I got from Griz last month was November - the 0484 date has been pushed to October. Amazon lists the 0159 as "in stock" at Griz, so I'll call tomorrow and get the straight scoop.
                    Chris
                    Merkel, Tx
                    http://raceabilene.com/kelly/hotrod

                    Comment


                    • #11
                      I used a standard LG 1hp VFD with my Griz 0519. It has never been a problem.

                      Comment


                      • #12
                        Originally posted by Falcon67
                        I must be missing something about how the VFD works in real life?
                        Yep.
                        On start up the VFD ramps up from 0 to 60 Hz (or your pot setting), it takes about 2 seconds, depending on your values and the load. This ramp up often takes the full current capacity of the electronics.
                        If you start the VFD without a load, the frequency comes up to speed, all is fine. Then if you switch in a motor, the current in rush is too much for the electronics, it will either shut down, or greatly reduce the life.
                        On a switched start up, the in rush is MANY times the current needed for the rated power of a motor.

                        Dave J.

                        Comment


                        • #13
                          Originally posted by mechanicalmagic
                          Yep.
                          On start up the VFD ramps up from 0 to 60 Hz (or your pot setting), it takes about 2 seconds, depending on your values and the load. This ramp up often takes the full current capacity of the electronics.
                          Actually it doesn't. Not with 2 seconds of acceleration and assuming a machine load like a lathe.



                          If you have the acceleration set to 0.1 seconds then yes.



                          Since the Griz draws 4.5 amps you want a 2 hp (7.5 amp) rated VFD. Better to have more capacity on the VFD than less.

                          Rewiring the Griz for a VFD is not terribly difficult. It is mostly just time consuming.
                          Last edited by Richard-TX; 08-17-2009, 08:52 AM.

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                          • #14
                            The Griz 0519 is a 1hp machine.

                            Comment


                            • #15
                              Originally posted by nheng
                              Falcon67, While you can control all motor functions from the VFD, it makes it more "natural" to use the machine if the original controls are used as logic inputs to the VFD, controlling the functions they used to do directly.
                              ...
                              This is the easiest way to do it. You can switch between the VFD and the motor but you require some kind of interlock that prevents switching when voltage is applied to the motor/s. If you cant provide the interlock go with the above.

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