drives and inverters capacitors 2

[fab1961]

Dear all,

I've been told that when a drive or an inverter is kept too long (say more than 2 years) in the store without connecting it to the supply you may need to take care of the internal capacitors - suggesting it may be better to send it back to manufacturer for a sort of reconditioning.
Is is something that can be made at one's shop avoiding the costs of shipping material back and forth?

Thank you

 

[Skogsgurra]

Yes. You can do the conditioning yourself.

Use a variac plus a rectifier plus a power resistor, say 100 ohms 100 W - or an incandescent lamp. Connect rectified AC via resistor to capacitor + and - and adjust voltage to around half the capacitor's rated voltage.

Watch current and let it stay at milliamps for a couple of hours.

Then increase voltage to capacitor's rated voltage and let current decrease to milliamps and stay there for another few hours.

If there are discharge resistors (very common), then the 'milliamps' will stay at a higher level, which can be calculated from applied voltage and resulting parallel resistor combination (if there are more of them, also very common).

Most manufacturers give detailed information in their corresponding drive manuals. Siemens has brought the 'formatting' to a high level - almost an art.

Some inverters have a 'self-formatting' feature that can be activated from the operator's panel.

CAREFUL! Lethal voltages present - make sure no-one can touch the drive when you are doing the comditioning!



Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

It's true, and the procedure is called "reforming" of the capacitors. A web search using that term will provide you with papers explaining why and some additional instructions, although Gunnar pretty much summed it up for you.

Gunnar, maybe you should write an FAQ for this forum on this?

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[oldfieldguy]

Lots of electronics contain electrolytic capacitors these days.

I had a client whose microprocessor-based relay went belly-up one Saturday night. I handled the call-out. He was very proud that they'd purchased a spare when we installed the first one. It had been sitting on a nice, dry shelf for five years. The power supply died on power-up.



old field guy