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Registered Member #3698
Joined: Sat Feb 19 2011, 11:31AM
Location: Rhinebeck, NY
Posts: 4
Nice resistors! Interesting project.....Depending on how permanent you want the enclosure Silicone RTV or a thermal conductive epoxy(Emmerson & Cummings) would negate the mess and headaches that oil introduces....getting a good seal is still a huge market issue today on oil-filled high voltages.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
gchickusa wrote ...
Nice resistors! Interesting project.....Depending on how permanent you want the enclosure Silicone RTV or a thermal conductive epoxy(Emmerson & Cummings) would negate the mess and headaches that oil introduces....getting a good seal is still a huge market issue today on oil-filled high voltages.
I was warned by the Application Engineers at Caddock:
*** To not use thermal epoxy, as it would place lengthwise force along the body of the resistor, then the resistor could crack and or change rsistence.
*** And not to depend on Silicone, as its thermal and specific heat are inferior to that of common oils.
Registered Member #3698
Joined: Sat Feb 19 2011, 11:31AM
Location: Rhinebeck, NY
Posts: 4
Interesting comments from Caddock.....in 30 years we haven't had any resistors crack under pressure in expoxy....only by arcing, and we use two different epoxies depending on thermal property(dissipation) requirements. The silicone RTV has no thermal hold off, which is fine if you're staying under 300 or 400 watts.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
I now use only two oils, for cheap cost i use Canola oil, for high quality i use yellow Olive oil.
For transformers and caps where the oil is part of the circuit i use Olive oil. For resistors and already potted elements i use Canola oil for heat dissipation and electrical insulation.
I will be getting a 100 micron vacuum pump in a few weeks so i can get good with the vacuum degassing and potting.
Registered Member #1521
Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128
Someone know where can be bought these SMD HV resistors in small quantity? There are 5kV ones, so building a resistor for 100 or 200kV would be really easy, and small. But I think they aren't cheap :(
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
omegalabs wrote ...
Someone know where can be bought these SMD HV resistors in small quantity? There are 5kV ones, so building a resistor for 100 or 200kV would be really easy, and small. But I think they aren't cheap :(
I dont knowof a reseller for Nicrom, i was going to buy from them directly, before i checked Ebay,and found all of mine cheaper that way.
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HV Resistors for HV measurement....
