| 摘要 |
A power converter typically used for operating electrical machines and provided with protective measures to protect against overvoltages which can otherwise occur in the process of switching off the inductive loads represented by the electrical machines. To that end, the converter includes plural bridge circuits having a.c. voltage terminals and d.c. voltage terminals, wherein the a.c. voltage terminals are phasewise parallel-connected and coupled to each other via at least one capacitor and wherein the d.c. voltage terminals are coupled to each other via at least one intermediate circuit reactor. The bridge circuits include bridge arms having GTO thyristors that can be switched off, and the plural bridges are driven out of phase with respect to one another. In this way, the converter supplies an alternating current which is relatively near-sinusoidal and exhibits a low harmonics content to the electrical machine. Following turning off of the thyristors in the bridge circuits of the converter, energy stored in the machine is temporarily stored in the capacitors coupling the A.C. terminals of the bridge circuits, so that no impermissible overvoltages occur.
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