Re: capacitive load on triacs

raseel wrote:

hai, iam designed a triac circuit to controll a capacitive load. The triac
used is BT139. I am not included a snubber circuit.Is that necessory
for capactive load??
Then how is the design the snubber components?? iam expecting a
positive reply..

RASEEL
"Snubber" circuite are used when inductors are being switched, due to the ringing / high voltages created by inductors (dI/dT).
So.. look at a circuit like the following: power supply feeds a resistor to a switch to ground (the triac) and the capacitor is in parallel with the switch.
Start with switch open - capacitor charges to supply voltage = is triac rated for that voltage (or more)?
Then close the switch (turn on triac) - large current flows from capacitor thru triac, limited only by inherent resistances of the circuit = is the I*I*T rating of the triac exceeded (pronounced "eye squared tee")?
Sadly that data appears to be very absent these days; 30-40 years ago that crucial design info was *published* as a part of the data *** specification of (power) thyratrons, ignitrons, SCRs and triacs.
That info is similar to SOAR or Safe Operating Area in power transistors and is absolutely necessary so that a designer can prevent device destruction.
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