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
BFL13 wrote:
A. Put one 5R 020 (5R 20a 200/300J)
C. two As in series (10R...)
Selection A is my first choice, but you could do C if you want to reduce the surge current even more, but I'm not sure its needed.
However, if you plan on performing hot restarts where the capacitor is completely discharged - I think you stated you did this, then you will damage either combination above.
The thermal time constant for the thermistor used in selection A or C is about 3 minutes and 14 seconds.
If you wait about 3 minutes and 14 seconds, the thermistor resistance will be about 3.14 ohms, which may be pushing the limits related to energy dissipation.
If you wait about 6 minutes and 28 seconds, the thermistor resistance will be about 4.3 ohms which is probably safe but the parts do have a +- 20% tolerance.
If you are anal, 5 time constants (which is about 16 minutes) will take the thermistor resistance back to it orginal, nominal, 5 ohm value.
When the thermistor has not cooled sufficiently, and the capacitor is completely discharged, the thermistor will dissipate much more energy which I believe is what is causing your failures...
