T810-600B-TR TRIAC Not Turning ON With Load

PDIhawk · ‎2023-08-28

I have a legacy project that I converted to an SMT design but the existing TRIAC is not meeting all specifications of the product. I am evaluating other options and one option that I'm looking at is the T810-600B-TR. In this application, the transistor is fully turned ON and passes 120VAC for up to 12ish minutes, then turns OFF. I have played around and can't get this part to fully turn on under load. The gate is drawing 14mA, gate voltage is 0.9V but the output is only 62VAC under a 500W load. However, when there is no load, the output is 117VAC.

Why wouldn't I be able to get this part to pass all of the input when it is under load?

PDIhawk · ‎2023-10-10

As I was digging into this problem, I was wondering why the existing circuit works given that there was no way to switch the gate to allow the full wave to pass. The existing circuit using the L6008D6RP essentially works but it over heats and latches in the ON state when running with max load and time. It worked without issue when it was the through hole version.

Seeing your suggestion makes a lot more sense to me than what I was starting from and I will have to look into designing in zero crossing control.

PDIhawk · ‎2023-10-16

Ok, after absorbing this problem more, I think that this circuit isn't that flawed because I don't really need to worry about zero cross switching and this works with a different TRIAC. This circuit turns the TRIAC ON at power up and once the timer has lapsed, the TRIAC is supposed to shut OFF. The only point that the zero cross would come into effect is at the start and end because it isn't periodically turning it on and off during operation.

AScha.3 · ‎2023-10-16

right. 🙂

but the MOCxxx triac driver giving a good trigger pulse to the triac , thats the point!

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PDIhawk · ‎2023-10-17

I'm understanding this even more now and see what you are talking about. I will be implementing a zero-crossing circuit to control the gate.

The only thing that I still don't understand is why the L6008 TRIAC works as long as I don't run it at full load.

PDIhawk · ‎2024-01-10

For an update:

I want to avoid single source parts, so I implemented a simple zero-crossing circuit using a bridge rectifier and opto as attached.

This still didn't get my device to operate using the T810-600B.

To get this project moving forward, I reverted back from the STmicro part to the L6008 TRIAC. My main problem with the L6008 was that it was just overheating under load. With a better heatsinking design, I was able to get the L6008 working without zero-crossing.