On/Off Power switch question

[madisonears]

I have a DPST toggle I intend to use for on/off power of a chip amp with 12k uF supply cap on each rail. The switch is rated for 10 amps. My 200VA transformer has dual primary/secondary windings.

Should I wire the switch
A) with one hot (or line) primary winding on each pole (switching both hot primaries separately, but simultaneously)
B) with both windings of both hot and neutral wired to each pole (switching both hot and neutral simultaneously)
C) with both windings of hot primary wired in parallel to both poles (redundant)

Peace,
Tom E

[infinia]

Originally posted by madisonears
C) with both windings of hot primary wired in parallel to both poles (redundant)

I've seen option C done on high power SS amps before without slow start, but you could mostly pick any.

Dont forget a spark noise cap across the pole.

[AndrewT]

B is normally used in the UK.

[infinia]

If seen B before esp. on lighted switches. Serves as way to easily connect neutral, but needs an extra cap as you can't guarantee which connection breaks first.

[star882]

If it runs from 120v, have a relay that initially wires it for 240v (half output voltage) for capacitor precharge and then switches to 120v wiring for normal operation. Even then, a NTC might be needed to further limit inrush current.

[lanchile]

I am using Inrush Current Limiters in the hot and neutral lines,I am using an DPST switch too. Inrush Current Limiters are among the most common design options used in switching power supplies to prevent damage caused by inrush current surges. A thermistor is a thermally-sensitive resistor with a resistance that changes significantly and predictably as a result of temperature changes. The resistance of a Surge Limiting thermistor decreases as its temperature increases. As the inrush current limiter self-heats, the current begins to flow through it. Its resistance begins to drop and a relatively small current flow charges the capacitors in the power supply. After the capacitors in the power supply become charged, the self heated inrush current limiter offers little resistance in the circuit. So low that the voltage drop is an insignificant factor with respect to the total voltage drop of the circuit.

[AndrewT]

Originally posted by lanchile
After the capacitors in the power supply become charged, the self heated inrush current limiter offers little resistance in the circuit. So low that the voltage drop is an insignificant factor with respect to the total voltage drop of the circuit.

Hi,
while the capacitors are charging the typical resistance of the Power Thermistor will be at it's lowest.
After the capacitors have charged the temperature of the Power Thermistor will drop and the resistance will increase.
Thereafter all changes in current draw will modulate the resistance of the Power Thermistor. This effect is very easy to see in testing. The modulation of voltage of the PSU is considerable.

I always recommend that the soft start and the slow charge resistors/thermistors be relay bypassed as soon as they have completed their intended purpose.