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:
This failure mode should then happen to all converters when they are toggled on-off-on in a short time period. I can toggle my Parallax or Iota converter without failure.
The energy the thermistor consumes in one cycle is:
E = I^2 * R * t
E = (120Vrms / 5ohm)^2 * 5ohm * 1/60Hz = 9.6 J
If the thermistor is hot and it's at 0.1 ohm, then the energy is 2400J. That would be an incorrect calculation as there's more resistance involved. We got the generator resistance, ac cable resistance, emi filter resistance and capacitor esr.
Sal
Using the specification sheet you provided, the hot resistance is 0.03 ohms...
Not a good idea to use a hot restart when the capacitors are fully discharged.
Five time constants is considered a full change in energy either way which is equal to 194 seconds x 5 = 970 seconds or approximately 16 minutes.
Oh, and the good news is that the initial surge current exists for about 1/4 of the 60 Hz cycle, and then it tapers off during the other half cycles, so the energy is actually less...
