SCR Can Be Switched From Non-conducting State To Conducting State In Following Way:
SCR Can Be Switched From Non-conducting State To Conducting State In Following Way Forward Voltage Triggering Thermal Triggering ( Temperature Triggering ) Radiation Triggering ( Light Triggering ) Gate Triggering 1 ) D.C Gate Triggering 2) A.C Gate Triggering 3) Pulse Gate Triggering
Forward Voltage Triggering :
Forward Voltage Triggering Anode to Cathode forward voltage is increased with gate circuit open. Reverse bias junction have an Avalanche Breakdown at Forward breakover voltage. SCR changes from ‘OFF’ ( High voltage with low leakage current )state to ‘ON’ (Low voltage with large forward current) state at this voltage.
Thermal Triggering:
Thermal Triggering Depletion layer decreases with rise in temperature Device is Triggered by increasing its junction temperature to a certain value. Reverse bias junction collapse and making the device conduct Radiation Triggering Energy is imported by radiation , like energy particle as photon Electron -Hole pair generated in the device Leads to instantaneous flow of current and trigger the device LASCR and LASCS
Gate Triggering :
Gate Triggering Most common method to trigger SCR. Positive voltage applied in the gate and cathode terminal , triggered much before breakover voltage. Three types of signal used , They are D.C signal A.C Signal and Pulse signal In D.C gate triggering d.c voltage of proper magnitude and polarity is applied to make the gate positive , it produces gate current and devices starts conducting AC triggering is done by changing the phase angle of applied signal In Pulse Triggering gate consist of high frequency periodic pulses with pulse transformer for frequency getting.