This is a turning ON method but it may lead to destruction of SCR and so it must be avoided.
When SCR is forward biased, junction ð½1 and ð½3 are forward biased and junction ð½2 is reversed biased so it behaves as if an insulator is place between two conducting plate. Here ð½1 and ð½3 acts as a conducting plate and ð½2 acts as an insulator. ð½2 is known as junction capacitor. So if we increase the rate of change of forward voltage instead of increasing the magnitude of voltage. Junction ð½2 breaks and starts conducting. A high value of changing current may damage the SCR. So SCR may be protected from high ð‘‘ð‘£/ð‘‘ð‘¡.
ð‘ž = ð‘ð‘£
ð¼ð‘Ž = ð‘ð‘‘ð‘£/ð‘‘ð‘¡
ð¼ð‘Ž ð›¼ð‘‘ð‘£/ð‘‘t