Triac is over heating

Thread Starter


Joined Aug 18, 2010
Hi, I am using MOC3020 optodriver triac which driving a MAC223 as power triac on heat sink through a 180 ohm resistor.
I am drawing about 5A on 225V. Everything ok but the triac is getting very hot even it is on a heat sink! the mac223 triac is rated 25A, 600V.
what should I use to reduce the heat on the mac223 power triac?


Joined Sep 20, 2005
First, how hot is hot?
180 ohms gate resistance seems a bit low to me for 225V, That´s 1.25A flowing into the gate, right? The datasheet says you should aim for cca 100mA.
Even without the gate dissipation, you are dropping 6.5W at 5A on that triac.


Joined Nov 30, 2010
I don't think jcon is using the 225 volts to drive the gate. I believe jcon is simply having difficulty getting a feel for what 6.5 watts can do to a semiconductor.

The solution is in learning how to calculate a proper heat sink starting with theta JC = 1.2 C/W.

datasheet attached.



Joined Oct 15, 2009
6.5W on that would be easy (with a nice big heatsink)...
Try pushing 10W through a TO-263-7 SMT mosfet in a 65 deg C ambient.. Not as fun.. Thats my task this week.
I am using 25A triac to on/off a 15A load( Air condition) The part is from ST( T2535-800G) . The controlling is done through MOC3063 opto isolator. The triac is getting overheated. What could be the problem? It is a n SMD package of DDpak2. I heve not used any heat sink. Please advice.