Capacitor Reforming, why it's needed? 3

[gsjhand]

Can anybody give me an Idea that why capacitor reforming is needed in the cases where a drive has been sitting on shelf for too long? I want to know what changes in capacitor if it's not been used for a long time? Is this required only for the capacitors which are connected to power circuit or is it needed for all the capacitors including the ones which are on control circuit boards?

 

[dpc]

It applies to electrolytic capacitors.

http://www.nmr.mgh.harvard.edu/~reese/electrolytics/#reform

 

[itsmoked]

Yep. So wherever they are could use the reforming method. It becomes hard to do on the logic boards.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Reforming is mostly (only, I would say) used for DC link capacitors in frequency inverters. I have seen an inverter where a rather big capacitor exploded when the inverter was started without reforming the capacitors. Loud bang, lots of aluminum foil all over the place and a big dent in the panel's door.

If the manufacturer says it shall be done - then do it.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[rawelk]

Here is a decent article on capacitor reforming [/LINK]which should answer many of your questions.

Also, consult the drive manufacturer's documentation, or give their engineering department a call. I know ABB goes into this in one of their PDF tech papers, and the manufacturer may have a specific procedure they prefer to follow.

 

[edison123]

Dayymn. Does this apply to power factor capacitors too ? In my rewind shop, I have over 500 KVAR pf correction capacitors which lie unpowered for days together and are used only during motor testing. Of course, when they are used, the voltage is applied gradually through a variac (to reduce motor inrush current) but typical time to reach full voltage level could be as low as a minute. Should I take more time in "reforming" these caps ?



Muthu

http://www.edison.co.in

 

[Skogsgurra]

No edison. It only applies to electrolytic capacitors. All AC capacitors are either paper or film type. So no need to worry.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[edison123]

Thanks Gunnar. Phew ...

Muthu

http://www.edison.co.in

 

[ozmosis]

Typically it is with VFD's where the unit has been unpowered for 2 years or so. A gentle introduction to the electrical world via a variable voltage is advised, for a few hours or so before applying full voltage.