Break over voltage of Finger Voltage
The minimum forward voltage when the gate is opened at which SCR starts conducting heavily is called the break over voltage. To specify this value the gate is in the open circuit condition and the junction temperature is at its maximum permitted value although VBO is still a function of dv/ dt. Though the SCR can be tumed on with gate open by making the supply voltage equal to break over voltage, but in practice the SCR is prated with supply voltage less than break over voltage and it is tumed on by applying a small to the gate. Commercially available SCR s have break over voltage from about 50V to 500V.