Efficiency analysis of contactless excitation power transmission realized by loosely coupled magnetic tank transformer

Power coupling realized by contactless magnetic tank transformer as new approach of rotator excitation in synchronous machine could replace brushes and slip rings of traditional excitation. For new contactless energy transfer system, analysis of working conditions and efficiency is very complex in order to guarantee stable and efficient running. According to characteristics of contactless excitation energy transfer system, mutual inductance model was used to describe the loosely coupled connection between primary and secondary winding. First, series & series harmonic compensation circuit was designed, and in order to obtain the stable system the harmonic frequency of primary zero phase angle and critical load resistance could be determined based on this circuit. Second, the ideal efficiency analysis mode was proposed to simplify efficiency analysis process. In this process, the ideal efficiency determined by load resistance was introduced into the expression of input and output power and made sure of the last efficiency of contactless excitation energy transfer system. Simulation and experiment indicate that analysis error of output power and efficiency based on ideal efficiency analysis mode is less than 0.05, and the trend of simulation under different load or frequency is coordinated with the trend of experiment when all stable running conditions are fulfilled. So this analysis mode not only fixes the structure and parameters of contactless excitation energy transfer system, but also has high accuracy in efficiency analysis process.