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 t_on: The turn-on time t_on 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 t_d: The delay time t_d is defined as the time interval between 10% of gate current and 10% of thyristor on-state current.
3. Rise Time t_r: 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.

Line Commutated (Turn-off) Thyristor Circuit

Two types of SCRs based on turn off time:

1. PHASE CONTROL SCR. eg.: t_q ≅ 60 μs, 200μs.
2. INVERTER GRADE SCR (or fast turn-off) SCR eg.: t_q ≅15 μs, 20 μs.

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

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