Asea Brown Boveri Ag

Jean-Francedillaois Ravot

Osvin Gaupp

Peter Dahler

Gerhard O Linhofer

Helmut Bilger

An inverter having a plurality of inverter bridges which operate in parallel and whose output voltage is summed by way of a transformer. The transformer has a number of primary windings and associated secondary windings which correspond to the number of inverter bridges. Each inverter bridge is connected on the output side to a primary winding. The secondary windings are connected in series to sum the output voltages. The transformer has a center tap which is grounded by a ground connection. The suppression of in-phase or common-mode interference currents flowing by the ground connection and the interference voltages associated therewith is achieved by dividing the secondary windings into a first and second identical partial secondary winding. The partial secondary windings are connected to one another in the center tap in such a way that the common-mode currents and voltages induced in the partial secondary windings mutually cancel.

Invertor with reduced common mode voltage

An invertor (15) includes a plurality of invertor bridges (B1, . . . ,B8), which are connected in parallel and whose output voltages are summed via a transformer (19). The transformer (19) has a number of primary windings (P1, . . . ,P8) and associated secondary windings (S1, . . . ,S8) which corresponds to the number of invertor bridges (B1, . . . ,B8). Each invertor bridge (B1, . . . ,B8) is connected on the output side to one of the primary windings (P1, . . . ,P8), and the secondary windings (S1, . . . ,S8) are connected in series to sum the output voltages. The transformer (19) has a center tap (23) which is grounded via a ground connection (24). Tertiary windings (T1, . . . ,T8) are assigned to the primary windings (P1, . . . ,P8) and to the secondary windings (S1, . . . ,S8). The tertiary windings (T1, . . . ,T8) are also connected to a common-mode filter (51). The common-mode filter (51) is tuned to common mode interference voltages associated with in-phase or common-mode interference currents flowing via the ground connection (24). Thus, a circuit is formed that attenuates or suppresses the in-phase or common-mode interference currents and the associated interference voltages.

Invertor with suppression of interference currents

In the case of a three-phase transformer which, per phase (U, V, W), has a primary-side winding (U.sub.PW, V.sub.PW, W.sub.PW) and a secondary-side winding (U.sub.SW, V.sub.SW, W.sub.SW), in-phase regulating windings (U.sub.L, V.sub.L, W.sub.L) are provided on each limb per phase (U, V, W). These in-phase regulating windings (U.sub.L, V.sub.L, W.sub.L) serve, by means of a tap switch 3 and a load switch 6, for in-phase regulation for the purpose of reactive volt-amperes distribution in electrical power supply networks. In addition, the in-phase regulating windings (U.sub.L, V.sub.L, W.sub.L) are operatively connected via a further load switch 5 and a further tap switch 4 to a booster transformer (2). The voltages across primary windings U.sub.B, V.sub.B, W.sub.B of the booster transformer 2 effect quadrature or phase-angle regulation of the phase voltages U.sub.P, V.sub.P, W.sub.P in the three-phase transformer 1.

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Chevry, France

Jean-Francedillaois Ravot