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The operation of DC-AC converters in most of researches is considered ideal and balanced but in practical applications no ideal and unbalanced cases must be considered. For instance semiconductor switches of a converter may have differences with together or switching circuit in an inverter may be unbalanced. This unbalance can produce additional harmonics such as even harmonics. This additional harmonics can cause many problems. For precise investigation of these harmonics, a model of inverter based on switching function model is presented in this paper. With this model, analytical relations of harmonics in unbalanced condition are obtained. This model is simple but precisely can show the effect of unbalance in switching of inverters. Analytical results for harmonics in unbalanced conditions in inverter switching are examined by MATLAB and PSCAD softwares.