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  • GS2 Drive E-Stop

    Well, i see in the basic configuration, there is no way to add an E-Stop button or signal to stop the drive. Seems you have to add a contactor or some kind of device to cut power. I needed to do the simple project using a GS2 drive. Wiring it up and using the keypad to control the drive, there is no safety to the unit. Is this odd for a drive? I haven't used many different brands, so was just wondering. I normally don't use the drive in its most simple configuration. Adding an E-stop required a few more components. Using a 120v single phase input would not be that bad to do, but when you are using 3 phase, that is a different story.


  • #2
    Very few drives have internal circuitry to perform the E-Stop (or Safe-Off) function. This directly decouples the drive signals such that no 'rotation' type output can occur. (There may still be voltage at the outputs but it will not be such that it can cause motor rotation.) If it doesn't have this (and even if it does it requires several external safety rated components to ensure its correct operation) you must provide the appropriate external disconnect.
    thePLCguy

    Bernie

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    • #3
      As a guy who has installed many, many drives, I never even trust the Safe-Off Function. Very pricey but I still add in an external contactor. I always tie them in to the ESTOP controller. If it's a high inertia load we have the main power on the timed contacts and the controls on the instant contacts, this allows the drive to bring the load to a stop before removing main power.

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      • #4
        You should be able to setup the GS2 like this also. You should be able to have the first source be the kepad and second source be the DIs. You can have the second source ramp to 0 speed (the estop relay would switch this signal).

        I used GS3 drives with modbus and two discrete modes. Normal operation was via modbus. There was estop logic around the DIs. If the estop was triggered by flame detect, the drives ramped to 0 speeed. If the estop was triggered by gas detector going off, the drives ramped to full speed.

        Here is the thread that I was asking about this on GS3
        https://forum.automationdirect.com/f...and-di-signals
        Last edited by g.mccormick; 01-10-2017, 02:00 PM.

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        • #5
          Originally posted by deep6ixed View Post
          As a guy who has installed many, many drives, I never even trust the Safe-Off Function. Very pricey but I still add in an external contactor. I always tie them in to the ESTOP controller. If it's a high inertia load we have the main power on the timed contacts and the controls on the instant contacts, this allows the drive to bring the load to a stop before removing main power.
          As a guy who has had to replace too many drives which have failed with a fault code of E39, I do not not trust the Safe Torque Off *feature*
          Had another fail about 4 months ago - on the same piece of CTRL-H CTRL-H CTRL-H CTRL-H equipment.

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          • #6
            signal to stop the drive
            You can program one of the multi-function inputs for 00 or 01 and they will serve as a stop input.

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            • #7
              Be careful not to confuse "E-Stop" with "Stop". A regular drive or PLC input can never ever be considered an "E-Stop". I too have worked on systems where "E-Stop" buttons were hard wired to VFD digital inputs, but all of those were violations of the rules and they got modified. I have also worked on VFDs that decided that a digital input was on and simply ran with no wires attached to them! If this thing can hurt someone, do it right...safety risk assessment and safety rated components.

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              • #8
                The best you're going to be able to do with a GS2 is to use a safety relay with timed and normal contacts. The normal safety contact would cause a controlled stop and then the timed contact would kill power to two safety contactors in series with aux feedback to the safety relay. Beware some of these drives are not designed to handle a lot of power cycles due to the low cost pre-charge circuits used. I've had pretty good luck with them but ideally I'd use a drive with redundant STO's if possible if you have to do a lot of E-stops.

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                • #9
                  Originally posted by Adisharr View Post
                  The best you're going to be able to do with a GS2 is to use a safety relay with timed and normal contacts. The normal safety contact would cause a controlled stop and then the timed contact would kill power to two safety contactors in series with aux feedback to the safety relay. Beware some of these drives are not designed to handle a lot of power cycles due to the low cost pre-charge circuits used. I've had pretty good luck with them but ideally I'd use a drive with redundant STO's if possible if you have to do a lot of E-stops.
                  Instead of the contactors being on the line side of the vfd, you can put them on the load side. That way you are not power cycling the drives tons.

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                  • #10
                    Originally posted by g.mccormick View Post

                    Instead of the contactors being on the line side of the vfd, you can put them on the load side. That way you are not power cycling the drives tons.
                    That's usually not recommended due to the potential damage to the drive as well as the loss of motor control. There's no way to do a category 1 stop.

                    That being said, I don't use drives w/o STO's anymore. In 2017, they should all have dual STO's as a standard feature. Drive safety is a recurring topic on many forums and it's always the same discussion. It's time for mfg's to step up their game and start complying to standards.
                    Last edited by Adisharr; 01-11-2017, 03:37 PM.

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                    • #11
                      Originally posted by Adisharr View Post

                      That's usually not recommended due to the potential damage to the drive as well as the loss of motor control. There's no way to do a category 1 stop.

                      That being said, I don't use drives w/o STO's anymore. In 2017, they should all have dual STO's as a standard feature. Drive safety is a recurring topic on many forums and it's always the same discussion. It's time for mfg's to step up their game and start complying to standards.
                      If you combined output contactor with time delay estop wouldn't that satisfy the motor control?

                      Instant estop contacts open and triggers drive multi-input thus causing drive to ramp to stop in X seconds.
                      estop timedelay contacts open in X+Y time, thus opening the contactor. The contactor is opened when motor is at 0spd.

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                      • #12
                        Originally posted by Adisharr View Post

                        That being said, I don't use drives w/o STO's anymore. In 2017, they should all have dual STO's as a standard feature. Drive safety is a recurring topic on many forums and it's always the same discussion. It's time for mfg's to step up their game and start complying to standards.
                        If the manufacturers can make an STO that doesn't (ITSELF) fail, rendering several benjamins worthless.

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