Commutation technique in the supply of electromagnetic actuators

This study presents some specific problems concerning the DC-AC commutation of the power converters used in frequency controlled electromagnetic actuators. Starting from the initial conditions imposed for a low-cost simple inverter used for driving an electromagnetic vibrator, two commutation possibilities are analysed (unmodulated voltages and simple modulated voltages). The harmonic analysis performed in this study, permitted the analytic determination of the load current distortion coefficient against the control angle in the case of simple modulated voltage. The energetic performances (the real power and the power factor) of the system were evaluated through the power factor, determined analytically as a function of the operating frequency and the control angle α. The influence of the control angle on the current distortion factor has been highlighted experimentally using a programmable source, which allowed the synthesis of different waveforms at different frequencies. The novelty of this study consists in the analysis of the influence of the control variable angle α on energy parameters of electromagnetic vibrators, which allows a lower distortion factor and an appropriate power factor, both at a lower cost and lower commutation losses compared with pulse width modulation converters. Section 1 presents the technologies using commutation techniques analysed in Sections 2 and 3; Section 4 represents an analysis of the energetic performances, whereas in Section 5 experimental results for a vibro-compaction equipment are presented.