Regulable transformer with tap changer for voltage regulation at a regulating transformer, which comprises a lower voltage winding and an upper voltage winding, comprising - at least two modules (M1, M2, M3, M4); wherein - the lower voltage winding or the upper voltage winding comprises a regulating winding and at least two part windings (W1, W2, W3, W4); - each module (M1...M4) comprises a respective one of the part windings (W1... W4) as well as two bridging-over paths on either side thereof; - each bridging-over path comprises a respective series circiut of two semiconductor switching elements (S1.1, S1.2; S1.3, S1.4; S2.1, S2.2; S2.3, S2.4; S3.1, S3.2; S3.3, S3.4; S4.1, S4.2; S4.3, S4.4); - a centre tap (M1.1, M1.2; M2.1, M2.2; M3.1, M3.2; M4.1, M4.2) is provided in each bridging-over path between its semiconductor switching elements (S1.1; S1.2;... S4.3 S4.4); - the part windings (W1... W4) have different numbers of windings; - in each module (M1... M4) a respective one of the two centre taps (M1.1; M2.1, M2.2; M3.1, M3.2; M4.2) is connected with a centre tap of the adjacent module; - the one remaining centre tap (M1.2) of the first module is connected with the load diverter and the one remaining centre tap (M3.1, M4.1) of the last module (M3; M4) is connectible with the regulating winding; - sub-voltages arise due to the different switching on, opposite switching or bridging over of the individual part windings (W1... W4); and - voltage steps (U ST) arise through addition of at least one of the sub-voltages to the step voltage of the regulating winding and/or through subtraction of at least one of the sub-voltages from the step voltage of the regulating winding; characterised in that - at least two of the voltage steps (U ST) can be produced in redundant manner. - at least two modules (M1, M2, M3, M4); - the lower voltage winding or the upper voltage winding comprises a regulating winding and at least two part windings (W1, W2, W3, W4); - each module (M1...M4) comprises a respective one of the part windings (W1... W4) as well as two bridging-over paths on either side thereof; - each bridging-over path comprises a respective series circiut of two semiconductor switching elements (S1.1, S1.2; S1.3, S1.4; S2.1, S2.2; S2.3, S2.4; S3.1, S3.2; S3.3, S3.4; S4.1, S4.2; S4.3, S4.4); - a centre tap (M1.1, M1.2; M2.1, M2.2; M3.1, M3.2; M4.1, M4.2) is provided in each bridging-over path between its semiconductor switching elements (S1.1; S1.2;... S4.3 S4.4); - the part windings (W1... W4) have different numbers of windings; - in each module (M1... M4) a respective one of the two centre taps (M1.1; M2.1, M2.2; M3.1, M3.2; M4.2) is connected with a centre tap of the adjacent module; - the one remaining centre tap (M1.2) of the first module is connected with the load diverter and the one remaining centre tap (M3.1, M4.1) of the last module (M3; M4) is connectible with the regulating winding; - sub-voltages arise due to the different switching on, opposite switching or bridging over of the individual part windings (W1... W4); and - voltage steps (U ST) arise through addition of at least one of the sub-voltages to the step voltage of the regulating winding and/or through subtraction of at least one of the sub-voltages from the step voltage of the regulating winding; - at least two of the voltage steps (U ST) can be produced in redundant manner.