Re: Case ground.

To: tesla-at-pupman-dot-com
Subject: Re: Case ground.
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
Date: Fri, 10 Jan 1997 07:02:36 -0800
Subscriber: bert.hickman-at-aquila-dot-com Sat Jan 11 10:19:06 1997

Tesla List wrote:
> 
> Subscriber: daniel_hess-at-VNET.IBM.COM Thu Jan  9 22:19:45 1997
> Date: Thu, 9 Jan 97 15:18:24 CST
> From: daniel_hess-at-VNET.IBM.COM
> To: tesla-at-pupman-dot-com
> 
> Subject:Case ground.
> 
> ground.  I prefer to have the primary circuit ungrounded and "floating"
> myself.  There is no electrical connection between the primary circuit and
> the secondary circuit.
> 
> What about the case of my neon transformers, (to house/water pipe
> ground)? They're connected center tap to the secondaries and therefore
> part of the primary.
> 
> Thanks, Daniel

Daniel,

There are a few reasons to tie the case to at least the RF ground:

Since large Electrostatic fields are present betweent the toroid and its
surroundings, the primary needs to have a path to ground to prevent
electrostatic induction from inducing high ES voltages (to ground) on
the entire primary. Grounding the neon case "bleeds" this off.

A pair of safety gaps should be used from each neon HV leg to the case
ground (and RF ground). This serves two purposes: it reduces overvolting
the neon's outputs, AND it provides a low-impedance path the the RF
ground in case you take a "hit" from the toroid to the primary. This
protects EACH leg, and prevents an RF flashover that otherwise would
find ground through your neon's secondary to the 120 VAC side... not a
good thing!

There's a belief that grounding the case reduced RFI, but I'm not aware
of any actual before-after measurements. The first two above should be
reason enough...

Safe coilin' to you!

-- Bert --