In the paper two sliding mode controlled inverter for fixed frequency AC power supply are described. After a brief review of the sliding mode control theory the way to obtain a switching frequency optimisation technique will be described for both inverters. The output transformer saturation problems will be described too. Simulation results are presented. In the last part of the paper the hardware implementation of the control and some experimental results relevant to a single phase, 5 kVA, 110 Vdc 220 Vac 50 Hz, and a three-phase 30 KVA, 350 Vdc, 380 Vac, 50 Hz IGBT inverters will be presented.