Converter In-Rush Thermistors etc, UPDATE -4
UPDATE on 17 Nov, Update 2 on 22 Nov, Update 3 on 16 Jan 14, Update 4 on 19 Oct 14. --------------- In a recent thread there was mention of how you can wreck your gizmo (in my case a converter) ...
Forum Discussion
Salvo wrote:
No surprise. Nothing had changed from the previous thermistor failure. We already knew the initial power-up was not the problem. The problem is P = I^2 * R. Where I is the 10A to 13A when converter starts operation and R is the resistance of the thermistor. The resistance is too high! Use 1 or 2 ohms. It probably also helps if a heatsink is attached to the thermistor.
Sal
It was when the thermistor was already warmed up so its R was low that it got hit with the big current from a "too soon" restart and blew, so how could it help to have a lower R thermistor for the cold start too?
I see the cold start with no load gets the thermistor warmed up and the capacitors done up when I then clamp on and the big current hits, so that is like I was trying not to do with a restart too soon. Same thing. So better to clamp on first. It works on a cold start clamping on last, but I can see there would be less chance of a cumulative effect breaking down the thermistor if I clamped on first.
As I am following the story here, the idea is to hit the thermistor with the high current before it gets warm so its R is still up.
