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Re: [TCML] Treadmill Motor Question

Isn't this the type thing that can kill a VFD (AC), or SCR (DC) speed controller? That's what I'd like to avoid. I'd like to "filter" all three phases to avoid VFD death, but haven't been successful so far.

Any advice would be welcome.

I finally snipped my response!

 From: "pterren@xxxxxxxxxxxx" <pterren@xxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx> 
Sent: Tuesday, September 10, 2013 8:06 PM
Subject: Re: [TCML] Treadmill Motor Question

I've seen DC rectifiers blow repeatedly on a museum coil.
My take on this is that there is likely to be differences in potential 
between the RF earth, HV feed and the mains feed to the ARSG motor.
This can be simply due to capacitance from the HV (the spark gap is very 
close to the motor), or voltage drop during spark events giving potentials 
across the small inductance leading to the RF earth for example.
It will only take a 500V transient to blow the diodes. So, how to prevent 
it? Not so easy.
My suggestions:
1 Completely shield the ARSG motor supply ie shield the mains cable to the 
motor and earth the shield to mains earth.  I have used adhesive aluminum 
tape over the motor mains cable for mine.
2 Use a microwave oven phi filter after the diodes. Cheap (free) and meant 
for AC but has caps, MOVs and inductors and will allow stray stuff to go to 
mains earth.
Maybe just the latter would be sufficient too.

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