it is necessary to select the optimum RG value from characteristics such as switching time, switching loss surge voltage and so on .Optimum RG should be selected with careful confirmation for no occurrence of any maximum rating violation (Tvj, Vces,etc) or any unexpected malfunction (arm-shoot-through, oscillation ,etc) at the actual application conditions. Too small RG may cause failure of IGBTs or FWDs. RG selection higher than its lower recommended value is strongly recommended. RG selection higher than its upper recommended value is not restricted ,unless switching loss incresase or any unexpected malfunction (arm-shoot -through, oscillation ,etc) are carefully checked.Sinec the surge voltage will change depending on the wiring inductance of the equipment and the snubber circuit etc, the optimum value varies depending on the user . In orde to maximize the decice performance ,it is recommended to individually set the gate resistance on turn-on side and turn-off side.