triac triggering

Discussion in 'General Electronics Chat' started by gjo, Oct 25, 2013.

  1. gjo

    Thread Starter New Member

    May 22, 2013
    28
    0
    If a triac is shorted what happens to gate current, does it still flow?
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    You mean if the main terminals of the triac are connected together does the gate current still flow? - Yes.

    Or do you mean if the load of the device the triac is part of is shorted? - Yes again, except the triac might not last very long unless you have some current limiting somewhere else in the circuit (sich as a fuse, circuit breaker, resistor, etc.).
     
  3. gjo

    Thread Starter New Member

    May 22, 2013
    28
    0
    If the triac is malfunctioning as a short
     
  4. gjo

    Thread Starter New Member

    May 22, 2013
    28
    0
    When the triac turns on without gate current
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,367
    A triac can be ON even when the gate current is reduced to zero.
    The triac current must be reduced to zero for it to turn OFF.
     
  6. TorontoBob

    New Member

    Oct 5, 2013
    15
    4
    A common failure mode of triacs is to short. They can also go open, but from my experience with driving large lamps, the triacs usually shorted with the lamp blew and there was a momentary current surge with the lamp filament burning up and an arc forming (why many lamps give a bright flash when they blow). But as MrChips says, once a triac has been turned on, the current through it must be reduced to below the holding current or to zero before it will turn off.
     
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