An on-board inverter controlled by the waveform switching technique

This work discusses operating principles and performance of a 400Hz sine-wave inverter intended for aerospace applications. Its operation is controlled in pulse-width modulation (PWM) on the basis of the "waveform switching" technique. According to this fully-digital design approach, digitised sinewaves are stored in a solid-state memory; a control circuit cyclically reads the waveform samples and correspondingly sets duty cycle for every transistor in output bridge. Amplitude control is provided by changing the digitised waveform to be reproduced in output, by means of a specific feedback circuit and of a memory with several sample sets stored, corresponding to sinewaves with different amplitude. Design of a prototype and its operation with reference to typical specifications for on-board power distribution systems are discussed