OT: Re: [sdiy] New synth DIY site ?

[J. Larry Hendry]

> ----- Original Message -----
> From: Magnus Danielson <cfmd at swipnet.se>
> Larry,
> Interesting construction by the way... but I am not
> all that impressed with the actual contact surface
> solution.

I will say it is not typical switch contact construction.  But, it works
quite well (all silver on the inside contact area).

> You could also explain how that thing is mechanically
>  controlled, since whatever electric/mechanic/pneumatic
>  control it is, it has to somehow make a 765kV jump....
>  or somebody likes to get deep-fried at work hours.

HA .   Actually, this is a circuit breaker disconnect (one phase of 3) that
is opened by means of manual crank.  Most disconnects are manually operated
as they are only isolating devices for the circuit breakers that actually
open or close the circuits.  The arc you see is simply the de-enrgized
switch blade coming into contact with the energized stationary contact.  The
current could be measured in milliamps.  In high voltage applications, the
actual interrupting capability (to stop the flow of crrent) of air
disconnect devices ranges from a maximum of about 7 amps to about 1/2 amp
which is what I would consider the limit for this one (due to the slow
nature of it's travel).  The interrupting rating centers around the speed
with which the contacts separate so that the path of ionized gasses in the
arc do not continue to be a conductor.  I have some 138 KV 6 amp photos
which are comsiderably more impressive just considering the size of the arc
(several feet).

Larry H