1
\$\begingroup\$

I am trying to control home devices using a microcontroller and a TRIAC. For switching, I intend to use an optocoupler and triac-based circuit. The circuit is given below (also plenty are available on the internet, but all are the same). enter image description here

The question I want to ask is how much power load I can connect to it's terminal because I need to connect a 230V-50A device at its output. So will this circuit, switch On/Off that device.

\$\endgroup\$
4
  • \$\begingroup\$ Consider using devices which integrate the isolator and the triac like: MOC302 \$\endgroup\$
    – stowoda
    May 10, 2019 at 5:29
  • 1
    \$\begingroup\$ 50A is near the limit for Triacs. High current designs often use back-to-back SCRs. IMO, you are also past the power limit where hobbyists should be. I have worked with high power stuff, and this is past where I would play with at home with discrete parts. If you can afford them, there are high-power Solid State Relays, these are more suitable for home hobbyists. digikey.com/product-detail/en/carlo-gavazzi-inc/RM1A23D75/… \$\endgroup\$
    – Mattman944
    May 10, 2019 at 7:52
  • \$\begingroup\$ @Mattman944 - I have opened one of these and they contain a triac + opto inside. Is there any benefit in buying these? Is your experience better than mine? \$\endgroup\$ May 10, 2019 at 14:55
  • 1
    \$\begingroup\$ @Whiskeyjack - Lower power modules will have a triac. Higher power modules like the one I referenced will have back-to-back SCRs. This module also has built-in zero switching circuitry (option A). The main benefit is safety, IMO inexperienced people should not be designing with high voltage, high current. You may be working with exposed high-voltage for a week while you try to get this to work reliably. Then if you are not careful, you will have a giant electrically hot heatsink. High-voltage at a few amps is different, that you can most likely get working quickly, minimizing the safety risk. \$\endgroup\$
    – Mattman944
    May 10, 2019 at 15:34

2 Answers 2

1
\$\begingroup\$

You need to provide more info. I feel you are misinterpreting the situation at hand. Assuming you are right, you will run into other problems than the circuit:

1) Supply: I could find only 4 triacs which meet the current requirements:

digikey

2) Heating: 50 A is a lot of current. Triacs will have a voltage drop across them when conducting. Approximately 1.3-1.6 volts. At 50 amps, you will be dissipating a minimum of 1.3x50 watts = 65 watts. This is a lot of power and you will need beefy heat-sinks with active cooling to get rid of this heat.

This video shows a guy making heat sinks for high wattage LEDs. Your case is more severe because LEDs convert some power to light. In your case, whole power is being converted to heat.

I read your comments on the other answer. No, R and C values are not the only difference when you are controlling 10 vs 50 amps. Snubber design is a topic in itself. However there are many things to take care of, especially the triac ratings and thermal design of the entire setup.

\$\endgroup\$
0
\$\begingroup\$

I want to ask is how much power load I can connect to it's terminal because I need to connect a 230V-50A device at its output. So will this circuit, switch On/Off that device.

Broadly saying yes, it will switch on and off the load.

The above is a standard TRIAC driver circuit. You need to select the TRIAC and snubbed circuit as per the load current, voltage and the nature of load.

\$\endgroup\$
2
  • \$\begingroup\$ Means if I am controlling a 10Amps load or a 50Amps load, the only difference between their circuits would be values of R and C of snubber circuit. So how do I select their values ? \$\endgroup\$ May 10, 2019 at 5:27
  • \$\begingroup\$ No, 1. important thing is you need to select a rated triac, 2. Select the gate driving resistor and driver based on gate characteristics. 3. select the snubbed circuit based on load characteristics. I am saying the approach will, be common.. you need to re-design everything from scratch by following the application note of that particular triac and driver \$\endgroup\$
    – Electron
    May 10, 2019 at 5:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.