Re: (Fwd) bleeder resistors used with MMC

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "huil888" <huil888@xxxxxxxxxxxx>

Oops ....... my mistake.

I thought Terry had tested the Phillips/Vishay VR37 resistors (1/2 Watt
series rated at 3500 VDC), but he actually tested the Yageo 1/2W carbon film
resistors, which are "rated" at only 350 volts maximumum working voltage/700
volts maximum overload voltage.

Since the VR37 resistors are easy to get, cost only a few cents more than
the basic carbon film resistors, and have almost 5X the working voltage
rating, I use them exclusively in my MMC arrays.

Regards,
Scott Hanson
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, November 03, 2006 5:53 AM
Subject: Re: (Fwd) bleeder resistors used with MMC


> Original poster: "huil888" <huil888@xxxxxxxxxxxx>
>
> DC -
>
> Not sure exactly what specific resistors you are talking about, but the
> Vishay VR37
> series of glazed metal film resistors (1/2 watt) are rated at 3500 VDC,
> and
> will actually withstand several times this voltage safely. These are only
> $0.08 each, even in small quantities, and have been used successfully for
> years as MMC
> bleeder resistors. They are available in values from 100K to 33M Ohms, and
> are described in the product literature as "high ohmic, high voltage,
> pulse rated" resistors.
> Allied Electronics usually has the 10M value in stock. Before Vishay took
> over the product line, these were marketed by Phillips. I think Our
> Moderator may have performed some voltage breakdown tests on these
> resistors way back in the dawn of MMC technology, but I couldn't find the
> report at Hot-Streamer dot com.
>
> http://www.pupman.com/listarchives/2000/November/msg00073.html
>
> Regards,
> Scott Hanson
> ----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Thursday, November 02, 2006 8:06 PM
> Subject: Re: (Fwd) bleeder resistors used with MMC
>
>
> > Original poster: "resonance" <resonance@xxxxxxxxxxxx>
> >
> >
> >
> > Better to use Allied Electronics pulse rated resistors --- 3.5 kV working
> > voltage.  Only 55 cents each.
> >
> > Although, I have never used any bleeder resistors in my AC NST powered
> > coils --- and have not found any holding a charge --- at least not in the
> > past 6 years!
> >
> > Dr. Resonance
> >
> > > My first thought was : What is Bill doing making such a small coil? Is it
> > > a toy one for Xmas.  Perhaps the Griffith Observatory (which you are
> > > doing
> > > if I recall) needs one for a small room like a toilet or broom cupboard?
> > >
> > > Resistors for MMC have been debated many times. Some people don't use
> > > any.
> > > Most use a single 1/2 watt 10M resistor per cap. This has always worried
> > > me as it is way overvolting the resistors rating of perhaps 500 - 800 V
> > > but in this pulse application they don't seem to fail.  Terry uses 4.7M x
> > > 2 per cap.  I use 3.3M x 3 per cap.  I don't think it has been proven who
> > > is right.  My guess is it depends on the application. For home use they
> > > are probably not required for a small coil. For a reliable larger museum
> > > coil you need to minimise failure modes, so use 3 or more.
> > >
> > > Peter
> > > http://tesladownunder.com