# Snubber circuit calculation.

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#### Ante

##### Full Member level 3
triac snubber circuit

Hi,

I need help calculating the snubber for a triac circuit. I use a BTA40-800B controlled by a MOC3063 to switch a transformer on / off. The Voltage is 400VAC and the transformer has a maximum power of 3kW. Can anyone assist please?

Thanks!

Ante :roll:

#### papyaki

snubber circuit

Hi,

check this old topic :

h**p://www.edaboard.com/viewtopic.php?t=80100&highlight=snubber

* = t

Papyaki

#### Ante

##### Full Member level 3
snubber calculator

Hi Guys,

Thanks, but I don’t even know if a snubber for a thyristor will work for a triac. Can you please help me with the maths for the specific components I use, it’s all Greek to me.
Thanks Guys!

#### IanP

snubber circuit calculation

Try to follow example (for triac) from this application note (page 12):

http://www.fairchildsemi.com/an/AN/AN-3008.pdf

Normally you choose damping factor and therefore whatever calculations you performe the result will be just rough idea of values (R and C) you should use in your application..

#### Ante

##### Full Member level 3
triac snubber calculation

Thanks Ian,

So what you are saying is that even if I follow the formulas the result will still be rough at best? I have built triac circuits before but only for resistive load and I have a feeling that the snubber circuits are more important when the load is inductive. Is there any substance in this reasoning?

#### IanP

snubber circuits

Everything because you have to assume to many factors (dumping factor, ...) Also, your indactive load in not pure indactor...

So the best you can do is to initially estimate values and then using an oscilloscope check shape of pulses (on and off) with several slightly different combinations of Rs and Cs.

points: 2