Critical Rate of Rise of Current
The maximum rate of increase of current during on state which the SCR can tolerate is called the critical rate of rise of current for the device. This is specified at maximum junction temperature. During initial period of turning on only a small area near the gate conducts the anode current. If the current increase too fast localized overheating may take place. This is called the hole storage effect. Due to localized heating the device may get permanently damaged. To day devices are available which can withstand rate o fries of current damaged. Up to 200- 250 a microsecond however in application this rate is hardly allowed to exceed beyond 5-10 a micro second. Protection against di/ dt is provided by series inductor.