Driving with inverters with low switching losses

Circuit arrangement for feeding a magnetically active and electrically operable operating means and including a driving arrangement, which circuit arrangement, in at least one first winding phase (S1), comprises:

• (a) a first branch (Z1) of a frequency converter (WR1) adapted for and operable at a switching frequency of not higher than 5 kHz for outputting a main alternating current generated at said switching frequency and having a substantially lower operating frequency (f1) to a winding (L1) of the magnetically active operating means (M);
• (b) a second branch (z1) of another frequency converter (WR2) adapted for and operable at a second switching frequency of more than 5 kHz for outputting a supplementary alternating current generated at said switching frequency to the same winding (L1);
• for superimposing, in the at least one winding (L1) of the operating means, the two alternating currents (iA(t), iB(t)) of the two branches (Z1, z1) to form a sum current during parallel operation of the first and second branches (Z1, z1) of the two non-identical converters for at least the first winding phase (S1) of the circuit arrangement, and wherein said driving arrangement comprises:
• (c) at least one current regulator (V1, V2) for the current having the higher switching frequency for regulating or controlling the sum current (i1) for at least the first winding phase (S1) and wherein the current regulator (V2) for the current having the higher switching frequency may be supplied with a difference between a nominal current value (inominal) for the first winding phase (S1) and a measured current (iA) at the output of the first branch (Z1).

Method for operating a circuit arrangement for feeding an electrically operated operating means having at least one winding (L1), which circuit arrangement comprises a driving arrangement and, in at least one first winding phase (S1):

• (a) a first branch (Z1) of a frequency converter (WR1) adapted for and operable at switching frequencies of not higher than 5 kHz, wherein a main alternating current (iA(t)) generated at said switching frequencies is output to the at least one winding (L1);
• (b) a second branch (z1) of another frequency converter (WR2) adapted for and operable at switching frequencies of more than 5 kHz, wherein a supplementary alternating current (iB(t)) generated at said switching frequencies is output to the same winding (L1);
• (c) wherein at least one current regulator (V1, V2) for the current generated at the higher switching frequency is provided for regulating or controlling a sum current (i1) for at least the first winding phase (S1) and wherein the current regulator (V2) for the current generated at the higher switching frequency is supplied with a difference between a nominal current value (inominal) for the first winding phase (S1) and a measured current (iA), as a nominal value, at the output of the first branch (Z1);
• wherein, in the at least one winding (L1) of the electrically operated operating means, the two alternating currents (iA(t), iB(t)) of the two branches (Z1, z1) are superimposed during parallel operation of the first and second branches (Z1, z1) of the two non-identical converters for at least the first winding phase (S1) of the circuit arrangement.