Re: SRSG motor - HELP!!!!!

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 6/9/02 10:40:09 AM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

<< Hello all,
 
< Today I was running my coil and getting solid 8 foot arcs, when
< suddenly, and rather destructively, the SRSG motor died. The motor is a
< 1HP bench grinder, which I had modified to run in sync. I think it is a
<capacitor run motor. Upon inspection, some of the windings were melted,
< and the entire motor was full of carbon. I saw no reason for it to fail.
< No sparks hit it while operating. It all happened rather suddenly. I
< have had some funny problems with this motor. Often, when applying
< power, it would just sit there and vibrate back and forth, as if it
< didn't know which way to spin. Could this just be because I stuffed up
< when grinding the flats (off centre, unequal size, etc)? Could this and
< the failure be related (was the motor drawing excess current, causing
< the wires to melt etc)? Before I go and buy a new grinder, are these
< motors suitable for this pupose, or are they doomed to fail?. It was
< definitely running in sync ok. Has anyone else successfully used one of
< these motors for sync operation?
 
< Cheers,
 
< Greg Peters
< Department of Earth Sciences,
< University of Queensland, Australia >>

Hi Greg,

I too have used bench grinder motors for RSGs except I've never
tried modifying one for synch operation yet. I had similar problems
with my RSG motors failing in Tesla duty in the past, though. I solved 
this problem by installing a standard surplus EMI filter in the line to the
motor (in addition to the filters for the HV transformer power supply).
I've been using the same 1/2 hp brench grinder motor ASYNCH 
for my 10 kVA pole pig system for the last 2 years with no problems
since installing the EMI power line filter in the line just before the 
motor. Try to keep the leads between the filter and the motor as
short as possible.

David Rieben