Which pin should drive Triac load ?

Forum|Forum|7 years ago
July 22, 2019
2 replies
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I am designing a typical TRIAC drive circuit, opto drive of the gate, snubber, transient protection etc. All app notes I read are saying that the load to be driven (in my case the primary side of a transformer) should be placed on the TRIAC's MT2 pin (I am using BTA26).

Is there something special about the GATE and MT1 relation that is effected by a load being driven at the MT1 pin? In fact, I prefer to have the inductive load at the MT2 pin, but the design may require that I put the load at the MT1 pin. The source voltage to be switched is L1 and Neutral (120VAC). Please advise.

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Best answer by Central SUPPORT

For best performance of the triac, it is recommended to connect the load on T2 and the mains on T1.

If the load is connected on T1, then the triac will be less immune, and especially more sensitive in terms of dV/dt, especially as the drive-signal will be referenced to a floating point when the triac is open.

In particular, this valid for sensitive triacs (low trigger current IGT).

Central SUPPORTAuthorBest answer

Senior

For best performance of the triac, it is recommended to connect the load on T2 and the mains on T1.

If the load is connected on T1, then the triac will be less immune, and especially more sensitive in terms of dV/dt, especially as the drive-signal will be referenced to a floating point when the triac is open.

In particular, this valid for sensitive triacs (low trigger current IGT).