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[email protected] pfjw@aol.com is offline
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Default Repairing A Variac

On Monday, April 30, 2018 at 1:57:01 PM UTC-4, John Robertson wrote:

Peter, does that have a suitable breakdown voltage for 130 - 150VAC? I
didn't bother sending the manufacturer my email address so they would
send me the docs to verify. However the ad says it is suitable for LEDs
and circuit boards, doesn't mention higher voltage applications.


John:

I must admit I am not sure. I used its functional equivalent on a Hot Tub control board switching 240 VAC heater and 120 VAC pump circuits without any problems - but for the heater on one just failed this weekend. Not the board, the heater itself. I suspect that the material you linked might be more suitable given its brush applicator and specific prescribed uses.

For the OP be really sure to clean between the windings where the arcing
occurred, you want to remove any sharp edges or points on the wire or
any carbon residue. There are dialectic varnishes designed for higher
voltages such as MG Chemicals Corona Dope:

https://www.mgchemicals.com/products...rona-dope-4226


The 'thing' about AC arcing is that once an arc is struck, the plasma generated helps sustain it. Hard to strike, but once struck not hard to maintain if there is a source for the plasma. Just a few weeks ago, a large Norway maple tree behind us started rubbing against a 13,200 primary. Those arcs made 6-8 inches until sufficient of the tree was eroded that the distance eventually was too much. PECO took nearly a week to get to it as the heavy snow and wind that caused the condition in the first place did far more damage elsewhere. 90 houses around us were without power for 4 days. We were exceedingly lucky not to.

When PECO did come, they worked from our back yard, and I got 'the dope' on arcing from their engineer on-site.

Peter Wieck
Melrose Park, PA