03-19-16, 07:51 PM | #18 | |
Supreme EcoRenovator
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Quote:
Relays will have some "bounce" in the contacts when they open or close, which could cause the mosfet to leave saturation. At 100VDC, driving a 13 ohm load, the mosfet would only survive a fraction of a second if it rose above a couple of ohms above its minimum resistance. Even on a big heat sink. A schmitt trigger or pulse stretcher are a few ideas that come to mind. Anything that makes sure the fet gets a nice discrete transition when changing states should make it last a long time. You definitely have something strange going on there. The IRF250 transistors you are using are heavier than what I would have started out with. They are pretty tough as far as power mosfets go. The only circuits I have seen these die in, they have been driving big flyback transformers. They throw lightning for a while before the mosfet finally dies. Another product I should mention for pipe joints is this stuff: I originally used this stuff in the Navy on joints that had to be watertight but easily separated for maintenance. Naturally, they had jars and buckets of the stuff, and it wasn't blue, but gray. Since then, I have used it on more surfaces than I can remember. It is a lot like the nylog sealant used on flare joints, made specifically for sealing machined surfaces, and for holding o-rings and gaskets in place during assembly. On threaded fittings, it works in places where pipe dope or thread tape leaks. OEM's like Jaguar, Harley Davidson, NASCAR, and Rolls Royce use it all the time. Like I have said before, I don't trust teflon thread tape. On pneumatic fittings, I will use it if nothing else is on hand. For anything hydraulic, I would rather run to the store. Last edited by jeff5may; 03-20-16 at 11:07 AM.. Reason: spelling |
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