CV Transformer - Capacitor on separate winding ?

[Randy McLaughlin]

From: "Tom Jennings" <tomj at wps.com>
Sent: Tuesday, May 03, 2005 2:11 PM


<snip>
> Allison is correct; I'd like to amplify on it.
>
> CV transformer power supplies are very inefficient; they draw tons
> of current and make a lot of heat.
>
> A CV transformer is basically a regular transformer with changes
> to the core and usually an added winding that has a capacitor on
> it. The extra winding and cap circuit is resonant at 60 (50) Hz as
> Allison points out.
>
> The core has a gap that makes it intentionally magnetically
> inefficient; the core is magnetically saturated; when the line
> voltage increases, more current flows, but no more magnetic field
> is generated, the extra power going up in heat. This is a
> "saturable core" transformer.
>
> They're run saturated, with excess input current, so that when the
> line voltage drops, the magnetic field does NOT drop -- because
> input power caused saturation, magnetic field was at maximum,
> dropping the line voltage to 100 (from 120, US) only lowers waste
> heat, the magnetic field stays the same.
>
> When the input goes below some point then yes, the output voltage
> will start to drop.
>
> THere's lots of variations, I don't know what your power supply
> uses.  Some put out "square" waves (clipped sines due to
> saturation), or regulated sine.
>
> Hard to imagine now, but this setup was once a lot cheaper than a
> switcher.

This system handles brown-outs, surges, huge spikes, etc.

It is especially handy in industrial areas that have heavy equpment 
destroying line quality.

These systems can create an audible hum.

For any delicate equipment in industrial areas you will often find 120/120 
or 240/240 ferro-resonate transformers added (especially for phone systems).


Randy
www.s100-manuals.com