Recently, while disassembling an old DVD player, I discovered that a 220 V power switch is connected in parallel to a 10 Nf capacitor with a voltage of 2 kV.Why is this being done?
This is necessary in order to reduce the sparking of the switch contacts and it will last longer.Sparking occurs under inductive load.
To see how it works, I took a 12-volt relay and disassembled it.By applying a voltage of 12 Volts to the relay winding, you can see how the relay contacts close and open.The relay contacts serve as an analog of the switch.By applying an alternating voltage of 13.5 Volts from a step-down mains transformer to an inductive load with an inductance of 250 uH, you can see a spark when switching relay contacts.
I took a capacitor X2 with a capacity of 0.22 uF and connected it in parallel to the relay contacts.And what happened? The relay contacts still spark, although the sparks are less than without a capacitor.
Now I took and connected a resistor with a resistance of 2 ohms in series to the capacitor.The sparks of the relay contacts disappeared.This simple RC circuit helped to get rid of sparks.
But it must be borne in mind that this only works with alternating voltage.If you connect the whole thing to a constant voltage, sparks will appear.
It should also be taken into account that an alternating current will flow into the load through a 0.22 uF capacitor with a power supply of 13.5 Volts, but its value will be less than 1 milliampere.This is under my conditions.For other voltages and load inductance, the values of the RC snubber must be changed.
