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I have some large voice coils in which the insulation is failing. We first notice this when the amplifier trips off on over current (short to ground.)

I'm wondering if before the catastrophic fault that there are small shorts between coils that could be an indicator of problems to come.

I know I can check resistance, but would a TDR be a useful tool? I'm wondering if I could see a change in distance before I could see a change in resistance.

JRE
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gamma_sponge
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  • What is causing the insulation to fail? Is it flaking off, or being carbonised? – Andrew Morton Jun 09 '23 at 20:21
  • A TDR isn’t a typical way to test impending insulation failure in a coil. Look into use of a “megohmmeter” or “megger” for nondestructive testing. A “hi pot” tester is more brutal and will provoke breakdown if the insulation is weak. – Mark Leavitt Jun 10 '23 at 05:36
  • We think the manufacturer used an improper potting compound. Our units are cooled by a di water mist. So it's a combination of heat, lots of stress, and DI water attacking it. We are going to limit when they are turned on in the future, but for now I'm trying to figure creative ways to detect an upcoming failure. – gamma_sponge Jun 10 '23 at 21:18
  • @gamma_sponge Maybe other users have encountered the same problem and the manufacturer has some method to fix it. You didn't mention if you'd contacted the manufacturer. – Andrew Morton Jun 11 '23 at 14:23
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    We have contacted the manufacturer and they are unwilling to change materials. We are meeting with another user of smaller coils who re-winds the coils themselves. It will be interesting to learn from them. – gamma_sponge Jun 12 '23 at 15:16

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