The maximum switching frequency of a 4.5 kV-400 A SiC-PiN diode and Si-IEGT hybrid pair module has been analyzed from the viewpoints of cooling capacity of the hybrid pair module and the minimum pulse width of the PWM signal. In the developed hybrid pair module, a direct water cooling type heat sink is employed to enhance the cooling capacity. It found that the developed 4.5 kV-400 A hybrid pair module could be operate at 10 kHz PWM switching frequency with the peak current of 110 A and the dc voltage of 2.5 kV. In this operating condition, the power losses of the Si-IEGT and SiC-PiN diode in the hybrid pair module are 2380W and 100 W, respectively.