vfd shelf life

I was just presented this question do VFD's have a shelf life specifically capacitor failures prematurely. I would think this should not be an issue, but I thought I would present it to the forum and see your thoughts.

Thanks
RM

Yes there is. It is VERY important.
If a VFD has been out of operation for a longer time, the capacitors have to be "formed".
There must be instructions from the manufacturer as to how long shelf time requires how much forming.

i was told the same as Jesper and we did see some with bad capacitors...

Reforming process in general is powering them with lower voltage for a while and increase voltage in steps for hours....

Some also count shelf duration for the warranty time out...

We have done the same and either tap into a lower side of a transformer or applied a lower voltage to the machine, we did for all controls not just the VFD's we had one machine pulled from production and sat in the boneyard for about 2 years then brought back to life, it had a bunch of Control Techniques drives, you also need to be careful as some electronics do not like low voltage

We also had a long term shutdown and we would power up the machines once a month and run everything manually just to make sure everything would start when needed

Thanks guys, Jesper answered my first question and Jeff answered the second one I was about to ask. I was not familiar with Capacitor forming. Good information!

It takes over a year of not being powered for the capacitors to begin to de-form, but you have to go by the date they were manufactured or taken out of service, not the date they were bought. If they have been unpowered for 2 years of more, you have to use the reforming procedure, between 1 and two years it’s iffy, so just never go more than a year and you are fine.

So if you have spare drives on the shelf, one simple way to deal with this as a preventative measure it is to take them off of the shelf once per year, hook them up to rated line power on a bench (with all due safety), let them sit there like that for a couple of hours then put them back on the shelf for another year. I make up a sticker for the box that charts the PM dates.

Bonitron sells a pre-packaged capacitor reformer. It’s spendy, but it’s hard to find the parts to do it on your own too. I bought one of the Bonitron units and I made one of my own with a variac, I think I spent maybe 20% more for the Bonitron when all was said and done, but if I value my time correctly, I lost money on the DIY version, plus the Bonitron comes with a nice roller case.
I take that one around to service calls, it’s paid for itself in under a year. (No, I don’t work for Bonitron...)
http://www.bonitron.com/m3628pcf.html

If you ever buy used or surplus drives, ALWAYS do the reforming procedure, never assume the seller is telling you the thuth. A LOT of used/surplus sellers have no idea this is an issue so they just tell you what they think you want to hear.