Gate Turn-On Characteristics of Thyristors

Figure shows the waveform of anode current as a function of time, following the application of a gate signal. The following time delays can be described from the waveforms:

 
  1. Turn-on Time ton: The turn-on time ton is defined as the time interval between 10% of steady-state gate current and 90% of steady-state thyristor on-state current.
  2. Delay Time td: The delay time td is defined as the time interval between 10% of gate current and 10% of thyristor on-state current.
  3. Rise Time tr: The rise time is defined as the time required for the anode current to rise from 10% of the on-state current to 90% of the on state current.
Gate Turn-On Characteristics
    Line Commutated (Turn-off) Thyristor Circuit
    Line Commutated (Turn-off) Thyristor Circuit
    Two types of SCRs based on turn off time:
    1. PHASE CONTROL SCR. eg.: tq ≅ 60 μs, 200μs.
    2. INVERTER GRADE SCR (or fast turn-off) SCR eg.: tq ≅15 μs, 20 μs.

    Asymmetric SCR (ASCR): tq = 4 μs, 10 μs.

    Forced Commutated Thyristor Circuit
    Forced Commutated Thyristor Circuit previous Turn-On of Thyristors
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