Series resonant inverters are the source of very high frequency energy and are used for high frequency applications. SRIs are connected to the load through high frequency transformers to improve the current gain. Inclusion of transformers and RL load leads to higher frequency harmonic components in the load voltage. Harmonic analysis of a basic SRIs (Class – A), feeding RL load: considering transformer parameters is considered. System is modelled first in continuous time domain and then harmonic analysis is carried out using MATLAB/SIMULINK. Whole analysis is extended to the discrete time domain approach for the analysis of the system. The response of the system is discretised using bi-linear transformation. A generalized algorithm for power series method is suggested for getting inverse z – transform, to obtain sampled data of the response (load voltage). Stability analysis in discrete time domain is carried out using the proposed approach for Modified Schur cohn criterion for a system in discrete time domain. FFT analysis is carried out on the sampled data using LAB View 7.0.