Subject:
Re: Cap break down voltages / Rotary Question
Date:
Thu, 10 Apr 1997 00:52:44 -0400 (EDT)
From:
richard hull <rhull-at-richmond.infi-dot-net>
To:
Tesla List <tesla-at-pupman-dot-com>
>Thanks Ed Sonderman, Richard Hull for your advise. Home made caps at
>10KV RMS are about right.
>
snip
>During this run the spark gap took a hit. For some odd reason the
>strike caused the electrodes on the rotary spark gap to colide, and self
>destruction followed.
>
>I would like to ask the list if the gap design I have is any good.
>Basically I have a high speed motor (10,000 rpm) and a rotor disk made
>from fiber glass PCB copper clad board. Two electrodes are mounted on
>the disk which are electrically connected by the copper covering.
>These electrodes pass two stationary electrodes with a clearance of
>about 0.5mm. I find that when the gap is running at operating speed
>the 6" disk streches and the 0.5mm gap closes almost to the point of
>collision.
>
>I calculate that with 1/4" electrodes the dwell time:
>
>velocity of electrodes is
> 6*3.14*10000/60 = 3140 inches per second
>
>dwell time is
> 0.25/3140 = 79uS
>
>Flaming round problems don't seem to be a problem. (No visable signs)
>
>The remaining rotor disk following the failure has lost an electrode.
>The electrode which is 1/8" diameter has ripped a grove from the point
>it was mounted to the outer edge of the disk. Is it possible that I am
>running the motor to the point of failure of fiber glass?
>
>Comments Welcome
>
>Julian Green
>
>Julian,
Wow! That is not common thin PC board material is it?!! Ouch! Killer
man!
If that is common PC board G-10 copper clad then you are one lucky guy!
I
won't run my 1/4" thick fiberglass disk above 3000 RPM! I am amazed a
thin
disk like than remained stable.
I would rethink the gap big time if I were you. good luck!
Richard Hull, TCBOR