Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx> Tesla list wrote:
Original poster: wysock@xxxxxxx ------- Forwarded message follows ------- From: Self <wysock@xxxxxxx> To: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx> Subject: bleeder resistors used with MMC Date sent: Thu, 02 Nov 2006 11:07:53 -0800 Terry, I've spent a lot of time surching the List archives and so far have not found an answer to my question. What would you recommend as the best size (in megohms I would presume), and wattage level to use with an MMC stack? I just bought 12 of the CD-942's and will be using all of them in series for a final cap rating of .012 mfd. I know many folks have used resistors to equalize the voltage distribution in these series strings. Unfortuantely, I never saved any of those posts to the List. Any help or advice you can give will be greatly appreciated. Best regards, Bill Wysock. ------- End of forwarded message -------
Hi Bill,The bleeder resistors won't do much in the way of equalizing voltage across the capacitor string(s) during TC operation. They really serve only to bleed off residual charge left on individual caps in the string. As Peter and Terry indicated, you may want to use 2-3 resistors in series across each cap to better share the transient voltage stress and get longer resistor life.
The time to bleed down to 5% of initial voltage (3 time constants) for 0.15 uF MMC caps will be T ~ 3*R*C = 0.45*R (T is in seconds, where R is total resistance across a given MMC cap, in megohms).
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