A detailed design process of the Z-source inverter is presented in this paper. A DC rail clamp circuit is used to reduce the overshoot of the device during turn off. The thermal and 3-D design process is gone through, and the loss calculation of the inverter is discussed, which is different from traditional PWM inverters. A 50 kW inverter for fuel cell vehicle is developed to demonstrate the validity of the design process. Experimental results confirmed the design process and demonstrated the high efficiency characteristic of the Z-source inverter