Re: Cap break down voltages / Rotary Question

        Re: Cap break down voltages / Rotary Question
        Thu, 10 Apr 1997 11:20:18 -0400 (EDT)

In a message dated 97-04-09 02:51:06 EDT, you write:

 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
 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

10,000 rpm might be too much stress for the disc.  You might be better
off to
add more electrodes and slow the motor down.  I also use a 10,000 rpm
with 16 electrodes (1/4" SS acorn nuts on each side with 1/4" shaft
the disc) and run the motor at 5,000 rpms or lower.  The high break rate
be a partial reason for the loss of my C.P. cap and I plan to run it
2,000 to 3,000 rpms in the future.  My disc is 3/8" polycarbonate.

Ed Sonderman