Re: Grounding of negative lead on SSTCs

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

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

Hi Marco,

On 22 Sep 2003, at 8:11, Tesla list wrote:

 > Original poster: Marco.Denicolai-at-tellabs-dot-com
 >
 > Hi all,
 >
 > I noticed on Dan's 15 kW SSTC schematics that the DC negative is
 > directly connected to the mains ground. I am used to see that done (and
 > do that) through a capacitor. I guess there is a safety issue here but I
 > can't recall the reason. Usually bench DC power supplies give the
 > possibily to externally ground the negative to the mains ground (and
 > chassis): it isn't readily wired.
 >
 > Can anybody recall/explain the reason why to do it in one or another
 > way?

Bench supplies are usually supplied DC-isolated from ground so that
one is not having to deal with a fixed negative ground rail (you can
ground the positive side of the supply if you like or even split a
single supply and ground the (electronic) centre-tap. A lot of bench
supplies are dual-section and allow tracking operation so the two can
be daisy-chained to form a split rail supply. You can then choose to
ground whichever part of the supply you like. In a word, flexibility.

      The capacitor to ground provides HF AC coupling so that any high
frequency components either coming from the supply or impressed on it
by the circuit it is powering are sent to ground.

Malcolm