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Triacs control

naumenkov123
Associate II

‎2018-05-12 10:44 AM - last edited on ‎2023-08-31 12:19 AM by

Posted on May 12, 2018 at 19:44

We used BT139X-600E triac. Opto triac MOC3052 used for triac's control.  Load is 230V, 50 Hz LED lamp, current is 30 mA. Current is not very nonlinear - it is short 'pulses' in the maximum of voltage 230 V.  The triac must withstand a short-circuit current of 100 A during 10 mS. The problem is that the triac sometimes does not turn on - the reason is most likely a very small current and a large current nonlinearity. We'd like to use BTA12-600BW. Maybe someone can tell what to do in this case?

TIA

Vladimir Naumenkov

www.agat.by

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Yannick Hague_O
Associate

‎2018-05-17 07:47 AM

Posted on May 17, 2018 at 16:47

Hello,

when using an opto-Triac, as soon as the power Triac is at ON-state, there is no more current flowing inside the opto-Triac and then no current flowing inside the power Triac gate anymore.

As a consequence, the power Triac will remain ON only if its A2-A1 current is higher than its proper Holding Current (IH) parameter.

So, with a very low power LOAD like LED 30 mA, a low IH Triac is required (but maybe even not sufficient as the current inside the lamp seems far from being sinusoidal).

ST T1610T-8FP in isolated fullpack package could be tried with Max IH at 25 °C at 15 mA (or BTA12-600TW).

The other source BT139X-600E IH is 45 mA max, typical value 4 mA, 25 °C.

OR (an maybe it is the only solution) a constant gate current must be maintained at the gate terminal.

Maintaining a gate current is requiring an auxiliary power supply linked to an opto-transistor in case isolated control is required like it is in this present case.

Let us know in case of any addition input is required.

Best Regards

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naumenkov123
Associate II
In response to Yannick Hague_O

‎2018-05-18 06:30 AM

Posted on May 18, 2018 at 13:30

Dear Mr. Yannick Hague, good day

Thank you.

You reported: '

OR (an maybe it is the only solution) a constant gate current must be maintained at the gate terminal.

Maintaining a gate current is requiring an auxiliary power supply linked to an opto-transistor in case isolated control is required like it is in this present case.'

Please, recommend a practice circuit with an auxiliary supply for maintaining a constant gate current

.

TIA

Sincerely,

Vladimir Naumenkov

www.agat.by

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