Why is there a 63V capacitor after the diode bridge?

Question

Electronic components

Why is there a 63V capacitor after the diode bridge? What makes it decrease?
If possible, tell me how to do the calculation.

Answer 1

look at the VS2 parameters and what it is in general + the principle of operation (googled as "db3 dinistor").
the purpose of the circuit to the right of the bridge is unclear, as well as the circuit as a whole.
if for a simple reason, then the "load" of the bridge is powered by a segment of the sinusoid "-30v ... 0v ... + 30v" through the EL1 lamp. the lamp itself is not turned on at this time and vice versa.

Answer 2

the voltage is limited not by the dinistor, but by the resistor R1.

This is a matter of terminology. In fact, if there were no dinistor, the voltage on C1 could increase further, but the dinistor does not allow this to happen when 30 volts are exceeded - it discharges C1 to the control input of the thyristor. So the limit chain is not R1, but R1+VS2.
By the way, this means that the initial section of the sinusoid (from 0 to 30 volts) is not used to light the lamp, which makes its brightness less than the nominal one.

Why is there a 63V capacitor after the diode bridge?

For the same reason - the voltage there (with the correct operation of the circuit, of course) should not reach 63 volts.