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?

 

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.

 

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.

 

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.

 

The triac is getting overheated. I have not used any heat sink. What could be the problem? It is a n SMD package of DDpak2. Please advice.

You basically just answered your own question.. You are clearly dissipating more than your design can support.
http://www.nxp.com/documents/application_note/AN10384.pdf