Re: NST replacements

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 07:37 AM 3/11/2003 -0700, you wrote:
>Original poster: "Scott Hanson by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <huil888-at-surfside-dot-net>
>
>Well, it might take a little work with an ohm meter to figure out what all
>the wires that emerge from the tar actually connect to.
>
>On the NST shown in the photographs from Hot-Streamer-dot-com, I believe there
>were nine wires coming up to the GFI module:
>
>(2) wires from the AC input terminals;
>(2) wires from each of the two primary windings;
>(2) wires from the momentary-contact "reset" button
>(2) wires from the LV end of the secondaries
>(1) wire from either from the "case ground" or "core ground" (I can't
>remember which)
>
>
>Every UL 2161-compliant transformer that I have taken apart has used two
>independent primaries; you just need to reconnect them in series.

I wonder why they use separate primaries.  Is it so they can balance the 
leakage currents to avoid false trips?



>Also, the common midpoint of the secondaries was connected to an isolated
>"midpoint return" terminal instead of being tied to the core structure.

Then, where does that midpoint go? Through circuitry to case/safety ground?