VFD Bus capacitor reforming Docs
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  1. #1
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    Default VFD Bus capacitor reforming Docs

    There have been a few posts lately again about how to reform caps in VFDs that has sat for 12+ months....

    Thought I would share a couple docs from 2 different manufacturers of VFDs and their individual methods.

    Dropbox - 215-6-29_Reforming capacitors after storage EN.pdf

    Dropbox - en_ACS8_Cap_reforming.pdf.pdf

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    Interesting....

    Especially as there is a chance they use the same capacitors!

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    In addition to the two given above ABB & REFU here are a couple more references.

    Yaskawa
    https://www.yaskawa.com/pycprd/looku...FrUZz5Ghccwe0=

    WEG
    ecatalog.weg.net/files/wegnet/WEG-how-to-reform-weg-vfd-capacitors-usareform-brochure-english.pdf

    Bonitron - Cap Reformer Manual, schematic and procedures.
    http://bonitron.com/Redirects/M3628PCF-ManualPDF.html

    Aug 2014 Thread covering the same issue.
    VFD Capacitor Reforming Procedure

    SAF Ω

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    Just shows, engineers have as many opinions as they have hands (or fingers), for any group of them! We have, in the list, instructions that vary in the time per step from 10 minutes, to several hours, and time at full voltage from a few minutes to 24 hours.

    Yaskawa says to step it up to full voltage, WEG says basically to slam it with 220V. The previous ones had different ideas entirely.

    And the capacitor technology is not significantly different between the different brands. Some may actually use the same brands of capacitor.

    For the record, the most sensible suggestion in my opinion is the Yaskawa procedure, which is essentially what I have recommended in the past, and would suggest be used. I'd leave it a little longer per step, but that's likely overkill.

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    Agreed on Yaskawa method. Similar to what we have done for years. Only difference is we put a 100watt light bulb in series with a diode off the variac and go right to the dc bus - besides limiting the current, it is a nice visual indication. But similar 5 minutes per 100 v or so, then sit half an hour near top voltage. So far we have not had complaints, and some of our 100-200kw specialized drives have sat for 5 years before finding a good home!

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    I just want to update the Yaskawa link. It's now at Procedure for Inverter Storage - Yaskawa

    Or just search their site for the "Procedure for Inverter Storage"

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    The large drives I have have a DC bus screw connection on one of the connection headers. I'm thinking about using a variac, transformer, diode bridge, and a 1800uF 450 VDC capacitor to construct a variable DC source. Then connect directly to the DC bus connection. I remember that jraef wrote that this is preferable compared with just powering the input side of the drive. I agree with this. SO if there is a choice than the direct DC bus method is better..

    I don't know if all those little drives like the Teco have the DC bus exposed to the user like that. I just looked into a Teco manual and the DC bus connection is not available. If the case comes off then there is a chance that a tie point will be available, or maybe there is a test point on a circuit board.


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