Question for JST and others about VFDs

I am putting two VFDs on a Heald cylindrical grinder. A reoccurring problem is people who turn on the power, do the job, hit the stop button for the motor in use, and walk away with the main switch still on. The problem with a VFD is increased because the power needs to stay on through the braking cycle. I have set up several machines with timers to delay startup for a few seconds to allow capacitors to charge and to hold the supply on for braking. Then everything will shut down with no effort on the operator's part. I can do that this time but some tech support folks have told me that it wasn't good for the drive to keep cycling the power on and off. In this case, I am considering keeping it on and putting a light at about eye level above the main switch where it would be impossible to ignore. Power would stay on for the duration of the job and only be turned off when it was finished.

From the viewpoint of life of the VFD, which is the better solution?

Bill

Turn-on is often a high stress situation as everything comes up to voltage, with high charging currents etc.

Leave it on and turn off when totally finished.

The only reason to turn it off sooner is a severe local electrical storm.

What about using a variac to slowly start the VFD and depower it?

Tom

TDegenhart said:

What about using a variac to slowly start the VFD and depower it?

Tom

Click to expand...

I'm sure that would help but this is in a shop where anyone can use the machine. We try as much as possible to keep it as simple as possible. It is hard enough to train them to turn off the modular 10EE. Since installing the Scissio solid state thyratrons, we at least don't have to worry about filament life on the hard to get tubes. We have spares for the field thyratron.

Thanks for the quick responses.

Bill

In the mills around here the drive is never shut off... just controlled with the run/ stop, I see no real need to shut the buss supply down, just leave it on.. the drives use very little power in that mode and will last for years...Phil