This document describes a methodology for identification of design errors in a two-level three-phase inverter prototype, with a 500VA/60Hz transformer for coupling to the power grid. The designed three-phase inverter, under test, uses a six IGBTs' bridge as main power switching elements, three single-phase transformers for coupling to the 220Vac/1KVA grid, measurement cards, trip control for the IGBTs and protection circuits. The methodology employed for this converter can be applied to industrial inverters of small and medium power.