High Voltage Resistors

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: High Voltage Resistors
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 2 Feb 1998 23:16:24 -0600
Approved: tesla-at-stic-dot-net

----------
From:  David [SMTP:davmckin-at-ix-dot-netcom-dot-com]
Sent:  Monday, February 02, 1998 1:45 AM
To:  Tesla List
Cc:  Correction-at-ix-dot-netcom-dot-com; to-at-ix-dot-netcom-dot-com; my-at-ix-dot-netcom-dot-com; e-mail-at-ix-dot-netcom-dot-com
Subject:  Re: High Voltage Resistors

Tesla List wrote:
> 
> ----------
> From:  davmckin [SMTP:davmckin-at-ix-dot-netcom-dot-com]
> Sent:  Sunday, February 01, 1998 5:30 AM
> To:  Tesla List
> Subject:  Re: High Voltage Resistors
> 
> Tesla List wrote:
> 
> > ----------
> > From:  Peter Naor [SMTP:QVR1.PETE-at-worldnet.att-dot-net]
> > Sent:  Friday, January 30, 1998 7:55 PM
> > To:  Tesla List
> > Subject:  High Voltage Resistors
> >
> > Hi to all!
> >
> > There is a lot of Email regarding capacitors and construction method
> > thereof!
> >
> >  I am interested in High Voltage resistors, non-inductive and their
> > composition! Is there a "home brew" type composition that will allow
> > control over resistor value, tempco and voltage rating?
> >
> > Regards,
> > Peter Naor
> 
> Dear Peter & all,
> 
using available resistors (usually > in the 10's k-ohm range)

This should read in the 10's MEG-Ohm range.  For example to
measure 50 kV one would need approximately 10.0 inches using
10 kV/in. (100 kV / 10 kV/inch = 10 in.).  Normal high voltage
design would be to use 4-1/2 inches of resistors (50 kV x 1.25/
15kV/in. = 4.17 in. rounded to 4-1/2 inches.  But for high
transient conditions in tesla coils, I would recommend being much
more conservative.  Also, plese note that these values are for
oil immersed usage only!

To read 50 kV on a 50 uA movement meter use a total of 500 Meg-Ohm.
This gives us 20 resistors x 25 Meg Ohm each.  Using I^2 R gives
us 5 Watts total for the divider / 20 resistors = 1/4 watt ea.
This will yield a current of 100 uA through the voltage divider.
Then using a meter with calibration resistor shunts, one can
establish 50 uA movement at 50 kV.  One thing to point out is
that instead of a 100 uA movement meter being used, a 50 uA
movement was used - this is for calibration purposes.

Hopefully, this will be of use to the group.

> David L. McKinnon
> High Voltage / Transformer Engineer
> 
> E-mail:  DavMcKin-at-ix-dot-netcom-dot-com