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Re: MMC resistor question
Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
Hi John,
See the repost below... I can't vouch for any other resistors, but the
ones I send with my caps are well tested at this "ludicrous" level. If you
need a bunch, let me know. They are all over the place here (on tables,
carpets, shelves...) I use them easily to 2000 volts. I know of no
failures of the resistors giving it up all by themselves.
Cheers,
Terry
At 05:19 PM 2/7/2001 -0500, you wrote:
>Terry, all,
>
>I noticed that common 1/2 watt resistors are generally used with
>MMC caps as bleeders. But these resistors are rated at about 370
>volts I believe? Has anyone had any problems with the resistors
>failing, or maybe contributing to MMC failure, due to tracking along
>the resistor, etc. I seem to remember that Terry did some testing
>of the resistors, and they seemed to be able to withstand a lot of
>over-volting. I didn't see anything about this subject of resistor voltage
>capability at your website Terry, but I may have missed it.
>
>Does it matter if the resistors are carbon film, or metal film, etc?
>
>Thanks,
>John Freau
>
Date: Tue, 26 Sep 2000 20:56:08 -0600
From: "Tesla list" <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com
Subject: MMC drain resistor study
Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
Hi All,
I fired up the Bertan HV power supply and tested some 10Meg ohm 1/2 watt
YEGEO resistors from DigiKey at high voltage. The results of a typical run
are:
Volts DC Current (mA) Power R(Mohms) Comments
1000 0.115 0.115 8.695
1200 0.138 0.165 8.696
1400 0.161 0.225 8.696
1600 0.184 0.294 8.696
1800 0.208 0.374 8.654
2000 0.233 0.466 8.584
2200 0.261 0.574 8.429
2400 0.290 0.696 8.276
2600 0.320 0.832 8.125
2800 0.351 0.982 7.977
3000 0.389 1.167 7.712 Drift
3200 0.428 1.370 7.477 Drift
3400 0.476 1.618 7.143 Drift
3600 0.548 1.973 6.569 Drift
3800 0.617 2.345 6.159 Drift Hey! what's burning!
4000 0.684 2.736 5.848 Drift up, then down
4200 0.701 2.944 5.991 Drift down
4400 0.719 3.163 5.841 Drift up
4600 0.762 3.505 6.037 Drift all over
4800 0.815 3.912 5.890 Drift all over
5000 --- --- she on fire now! ;-))
So It looks like they are perfectly good to 1600 volts and probably to 2000
RMS. That is like 2828 AC! This is at the low end of the Bertan's range
so there is probably some significant calibration error but you get the
idea...
I also tested two 1600 volt 0.56 uF Panasonic caps and they broke down at
4100 and 4800 volts and seemed to self heal in stride... Numbers like
these explain why MMC's are so darn tough!!
Cheers,
Terry