Anordning för omvandling av likspänning till en trefasväxelspänning genom pulsbreddsmodulering

摘要

In a device for converting direct voltage into a three phase alternating voltage having a two level converter connected to a direct voltage network and an alternating voltage network a control apparatus for performing pulse width modulation is adapted to determine the pulse width modulation pattern for each phase by using a triangle wave (19-21) with the same fundamental frequency as the triangle waves for the other phases, invert this an even number of times during a fundamental oscillation of the reference alternating voltage (24-26) and position the instants of inversions of each triangle wave so in the time that always two triangle waves are half a period displaced with respect to the third.