alt.engineering.electrical

On 9/16/07 5:11 PM, in article 5l5v1aF6g5i7U1@ , "Charles
Perry" wrote:

> The Powersave posts remind me of something that happened at my previous
> employer about a decade ago. This guy contacted us wanting us to evaluate a
> product he had invested in. He wanted some kind of letter of recommendation
> from us. He brought his product over (I won't post the name - although they
> are still on the market) for us to evaluate. It was a typical metal box
> that saved energy and made motors run cooler. He first demonstrated it
> using the "tools" he had been provided by the company. We, of course,
> pulled out real test equipment. It took about 5 minutes to figure out that
> what he had was a metal box full of capacitors. The real funny thing was
> that when he plugged it in one outlet, the votlage distorted horribly. The
> cap was acting as a third harmonic filter and was drawing huge third
> harmonic currents.

I must be missing something. How do capacitors draw high third harmonic
currents? Were they series tuned to the third harmonic? Even so, there would
be little third harmonic current if there were not something nonlinear to
produce a third harmonic voltage.
--
Iraq: About three Virginia Techs a month