OT: Drive + Plug + Motor

Existing Situation: 5HP sump pump. ABB ACS5500 drive. Sump pump connects to Meltric decontactor plug which then connects to the drive.

The pump mounts on a bayonett pipe fitting for quick lift and replace, so the plug is required for fast swap.

Push the release button on the decontactor receptacle and springs eject the plug. I'm a little concerned about what will happen if someone releases the decontactor plug while the sump pump is running.

Will the drive merely fault? Will that let the smoke out of something?

Other than a large flash if the motor is working hard, the drive will not be hurt. It may not even fault if it is operating in Scalar or V/Hz mode. It will surely fault if running in Vector mode.

Do not try to plug the motor back in without first stopping the drive. Plugging a stationary motor into a running drive is pretty much the same as throwing a short across the output terminals. It will surely fault and possibly destroy the output IGBT's as well.

Be sure the drive has stopped or, better yet, power down. Then reconnect and restart.

That large flash when disconnecting is dangerous and mostly unnecessary. Stop the drive first and then unplug. How hard can that be?

Stop first then disconnect is the standard procedure. I was just wondering what will happen when Otis doesn't follow procedure. However, Otis always follows procedure.

Disconnecting the while the IGBT's are conducting can blow you IGBT's also. I have had that very thing happen with that same brand of connectors here. Operations do it all the time even with a clear procude that states not to. It has stopped in the areas where we have cameras and will soon stop site wide.

Connecting while running is worse and will almost always release smoke (IGBT's)and can produce an arc flash.

I use a lot of the Meltric connectors also. I wish they had some kind of contact interlock that would open before the per contacts to disable the drive first.

That would be a neat new product for any Meltric employee's out there

The Plc Kid said:

I wish they had some kind of contact interlock that would open before the per contacts to disable the drive first.

That would be a neat new product for any Meltric employee's out there

Click to expand...

I see an "Auxiliary/Pilot Contacts" option for the 30A and larger plugs, but I don't know if they break earlier than the main contacts...



-Eric

The aux contacts open with the line contacts. My connectors have the aux contacts wired together in the plug to give plug inserted status to the PLC. So the drive won't be running when inserted. I'm still concerned about disconnecting when running.

Mennekes makes some similar connectors with interlocks that might solve your problem.

While it has been true for many years that disconnecting motor leads while a drive is working is destructive to IGBT's and is still true for many brands, ABB now warrants their drives to be tolerant of that without damage.

The flash, however, is still present and I, for one, would not like to have the hair on my hands and arms burnt off with one.

I got a hold of the local ABB field engineer and he indicated that the drive controls are fast enough to protect the IGBTs should the motor leads be opened. He confirmed what Dick said, that in scalar mode it probably won't fault, but in vector mode it would most definitely fault. These pumps run in vector mode. He said it may or may not flash, so I'll just assume that it will.

One nice thing about the Meltric plug and similar products is the shroud and pin shutters. When the release button is pressed the pins are ejected by springs, breaking electrical contact but not releasing the plug. The plug then has to be twisted ~1/8 turn and pulled out. The shroud is the last part to release. That should protect from the flash.

It is apparent that I need to place some warning labeling above the two plugs about the flash and about stopping the pump first. I think that otherwise the situation is probably OK.