Problem with TRIAC and resistive load

Thread Starter

MPYC

Joined Apr 17, 2015
14
Hi
I used circuit below. it seems simple. it works properly but after some while the BT136 born.
I guess it's lead by dI/dT limitation.
let me know about your ideas? how can I solve the problem?


 
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Dodgydave

Joined Jun 22, 2012
9,162
The opto-coupler has to connect G to MT2 for the triac to operate, and a 4K7 resistor between MT1 and Gate to prevent false triggering.
 

Thread Starter

MPYC

Joined Apr 17, 2015
14
The opto-coupler has to connect G to MT2 for the triac to operate, and a 4K7 resistor between MT1 and Gate to prevent false triggering.
I drive an AC motor perfectly. 40w and 60w single phase AC motor. I have Snobber and it's complete.
but TRIAC born after several months when I use bulb lamps.
 
Last edited:

marcf

Joined Dec 29, 2014
259
100w and 60w. I saw it in both powers.
heatsink, no but it's not warm.
A 100watt 20 volt bulb will draw 5amps. The current handling limit for this TRIAC is 5amps.

Also the bulb will have a very low resistance (1/10 to 1/100th cold vs warm) as it turns on.

It could demand over 1KW initially. This would be limited by your power source, but it easily could exceed the 25Amp for 20msec max spec stated on the data sheet.

Is this a aircraft landing light?

No wonder the triac is failing.
 

ebp

Joined Feb 8, 2018
2,332
A triac in TO-220 operating at 5 amperes would be very hot if operated without a heatsink. Even 2 A of average current would raise the package temperature to around 100 °C.
 
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