DamianInRochester
Lifetime Supporting Member
I am not a big fan of placing contactors on the ouput of VFDs.
We are working on a machine that was brought in from China. It utilizes Lenze 9300 drives. It is a web handling machine so the risks are getting pulled into pull roll nips and winders, etc. Interestingly, the Chinese did not see fit to install any type of disconnecting means for any of the drives.
Normally, I like to just put a disconnect on the line side and also give the drive a "quick stop" signal simultaneously with the Contactor dropping out. This way the drive uses the rest of the stored energy to help bring the motor to a stop quicker.
What complicates this arrangement is that all drives (six in total) all have their busses tied together. These busses all go to a global DB brake that dumps the buss to a resistor.
Therefore, if I drop the contactor out on say the winder section of the machine, it will still be getting power from all the other drives.
So .... I am thinking of putting the contactors instead on the output of each drive. I would put a saftey PLC in. When an estop occurs i would first give the drives a "quick stop" signal. A short time later I would drop the enable input to the drive to turn off the output semiconductors. Then finally I would drop the contactors on the output.
Any thoughts? Anyone else have experience in a case where the drives are all buss connected?
We are working on a machine that was brought in from China. It utilizes Lenze 9300 drives. It is a web handling machine so the risks are getting pulled into pull roll nips and winders, etc. Interestingly, the Chinese did not see fit to install any type of disconnecting means for any of the drives.
Normally, I like to just put a disconnect on the line side and also give the drive a "quick stop" signal simultaneously with the Contactor dropping out. This way the drive uses the rest of the stored energy to help bring the motor to a stop quicker.
What complicates this arrangement is that all drives (six in total) all have their busses tied together. These busses all go to a global DB brake that dumps the buss to a resistor.
Therefore, if I drop the contactor out on say the winder section of the machine, it will still be getting power from all the other drives.
So .... I am thinking of putting the contactors instead on the output of each drive. I would put a saftey PLC in. When an estop occurs i would first give the drives a "quick stop" signal. A short time later I would drop the enable input to the drive to turn off the output semiconductors. Then finally I would drop the contactors on the output.
Any thoughts? Anyone else have experience in a case where the drives are all buss connected?