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
Not that difficult. Put your camera in move mode and record the action. You can easily acquire the transient at a 5 ms/div sweep rate.
My scope plot of Parallax converter (way back from page 28).
Vert: 20V/div, Horz: 5 ms/div
The waveform has a linear ramp, charging to about 75V in 5 ms during the first cycle. Since the capacitor charge rate is constant we can deduct that the current is also constant (through most of the cycle). The steeper the slope, the greater the charging current. Subsequent charge cycles have lower current.
The current is:
I = C * dV/dt
I = 2400 uF * 75V/5 ms
I = 36A
The 2 ohm thermistor limits current to 36A.
Sal
My scope plot of Parallax converter (way back from page 28).
Vert: 20V/div, Horz: 5 ms/div
The waveform has a linear ramp, charging to about 75V in 5 ms during the first cycle. Since the capacitor charge rate is constant we can deduct that the current is also constant (through most of the cycle). The steeper the slope, the greater the charging current. Subsequent charge cycles have lower current.
The current is:
I = C * dV/dt
I = 2400 uF * 75V/5 ms
I = 36A
The 2 ohm thermistor limits current to 36A.
Sal
DryCamper11 wrote:
I might start watching things with my scope to see if I could figure out what was happening that was causing the failure. However transients are hard to find.
