RE: RE: Variable phase adj. cap size, braking action

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

Original poster: "brianb by way of Terry Fritz <twftesla-at-qwest-dot-net>" <brianb-at-antelecom-dot-net>

Greg,

My experience with 1/3, 1/2 and 3/4hp motors showed there is always some
breaking but it's usually not a problem till you get too big (then it stops
in a fraction of a second). Here is an old E-mail I sent to John F. when I
was working on some 1/2hp motors...

>  Today's setup used a W10 Variac, various combinations of motor run caps,
and
> 12" rotor with eight 1/4" electrodes. Neither of my motors uses a run cap.
>
>  With the 1800rpm 1/2hp motor 180ufd was the optimal value. This provided
a
> full 45-degrees of adjustment, 2-volt change over the Variac's range,
smooth
> operation, and very little braking after the power was removed. A smaller
> capacitance (135ufd) caused the voltage to plummet and the motor to loose
> sync as the inductor (Variac) was adjusted. A larger capacitor (203ufd)
> worked but the resonant rise was over 10-volts, the motor did not run
> smoothly, and there was two times during the spin down when there was a
> pronounced braking. Higher capacitance caused resonant rise in the 25+
volt
> range, surging, and NASTY braking issues when the power was removed.
>
>  With the 3600rpm 1/2hp motor 270ufd was the closest to optimal I could
> obtain with the caps I had on hand. This configuration provided a full 90-
> degrees of adjustment, 2-volt change over the Variac's range, and smooth
> operation. However there was some braking during spin down and it looses
sync
> if the Variac turned past 75%. This leads me to believe I'm close to the
> correct capacitance but not quite there yet. A smaller capacitance
(202ufd)
> caused the voltage to plummet and the motor to loose sync as the inductor
was
> adjusted. A larger capacitor (338ufd) produced a resonant rise well over
15-
> volts and there was a point during the spin down when there was a
pronounced
> braking.

Regards,
Brian B.

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, June 24, 2002 10:38 AM
To: tesla-at-pupman-dot-com
Subject: Re: RE: Variable phase adj. cap size, braking action


Original poster: "Mr Gregory Peters by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>

Will the braking action occur ONLY if the cap is too big, or will it
always occur, but just be more significant if the cap is too big? How
can it be avoided? Will turning the variac to zero inductance before
turning off prevent this problem? I have to buy these caps new, so I was
just hoping for a ballpark minimum figure to start at to save me some money.

Cheers,

Greg Peters
Department of Earth Sciences,
University of Queensland, Australia
Phone: 0402 841 677
http://www.geocities-dot-com/gregjpeters