| 摘要 |
The method is used in the case of a pulse converter whose switchable semiconductor elements are driven by control pulses which are produced by means of a periodic auxiliary voltage (UH) via pulse-duration modulation (PDM) of a plurality of reference voltages (UR, UY, UB). In this case, above a specific modulation level or ratio of the pulse frequency of the auxiliary voltage to the fundamental frequency of the reference voltages, a transition is made to a specific synchronous PDM. In this case, a change is made from a selected oscillation state of the auxiliary voltage to its pulse frequency for an entire cycle (TW) such that the transition to the synchronous PDM takes place in the same oscillation state and the auxiliary voltage response has no discontinuity. In consequence, transient asymmetries and frequency jumps are avoided in a multi-phase AC system which is produced at the output of the pulse converter. <IMAGE>
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