Phase-shifting transformers of round shape used for multi-module inverters

In multi-module inverter systems, phase-shifting transformers are needed to compose non-sinusoidal voltages into staircase waveforms That are close to sinusoid. In order to overcome the drawbacks of normal phase-shifting transformers with respect of installation and performance the paper proposes a novel transformer of round shape resembling induction motor. In contrast with In contrast with normal phase-shifting transformers, the iron core of the novel transformer is more compact and symmetrical, and the windings distribution and connection are simpler. Focusing on novel transformer of dual Y/ Y, the paper theoretically proves that harmonics of the 5th, 7th etc. are eliminated from the composed magneto motive force (MMF), and it is numerically verified by means of finite element method. Mathematic model of the novel transformer is set up and simulated for exhibiting the main performance. Finally, based on the prototype included in a multi-module inverter system, validity of the novel transformer is verified, and some critical performances are tested for evaluation.