Switching characteristics of resonance based ZCZVT (Zero Current Zero Voltage Transition) PWM (Pulse Width Modulation) soft-transition inverters analyzed; methods of increasing efficiency and reliability testing were focused on. Several soft-transition inverter structures are developed to eliminate the inadequacies of hard-switched inverters. Electrical circuit analysis is performed using the software ORCAD 10.5. and Micro-Cap 8 Guap Edition. This inverter operates with soft switching at high frequencies under a wide range of line and load voltages. The new proposed circuit includes the characteristics of the desired circuits beforehand. DC bus voltage is gradually modified by the new circuit consisting of magnetic coupling inductor with common air gap. Simultaneously, switching frequency is increased up to 51,02 kHz without any problems. A number of reliability test methods and a plan were proposed for the switching inverter circuit and reliability MTBF calculations performed using the Relex Software in accordance with Mil-Std-217F. Copyright (C) 2011 Praise Worthy Prize S.r.l. - All rights reserved.