thyristor turn on

Discussion in 'General Electronics Chat' started by saurabh1234, Nov 18, 2009.

  1. saurabh1234

    Thread Starter New Member

    Nov 13, 2009
    why is it preferable to use multiple short duration pulses for triggering scr??
  2. JDT

    Well-Known Member

    Feb 12, 2009
    Some reasons I can think of:-
    1. Because you can - once the thyristor is on it stays on until commutated.
    2. Allows the use of small pulse transformers for isolating the gate signal. Useful when the thyristor is at power-line voltages.
    3. Reduces average power dissipation in the driver circuit (short high-current pulse).
    4. Guarantees that the thyristor will turn off when commutated (forward current falls to low value) without having to worry about removing the gate current first.

    Sometimes, when controlling difficult loads - mainly inductive, or brushed motors where there may be momentary breaks in the current flow - the thyristor is fed with a series of pulses throughout the on period instead of just 1 pulse at the start.