Reduction of the electrical resistance for an electric machine having windings arranged in grooves

The invention relates to an electric machine having grooves and windings of electrical conductors, wherein the windings are divided into strands, wherein at least one strand has a respective number s of coils (1) connected in series, which are each arranged in the grooves, wherein the coils (1) each comprise sub-conductors (2) connected in parallel, wherein the sub-conductors (2) of a coil (1) are arranged in a plurality of bundles (3), wherein a bundle (3) of a coil (1) is connected in series to a bundle (3) of a coil (1) connected in series (3), wherein each bundle (3) of the at least one strand is arranged in a groove at a respective bundle position in relation to a deepest possible bundle position in the groove, wherein the respective bundle positions of all bundles (3) in all coils (1) of the at least one strand define a respective number b of possible bundle positions of the at least one strand. In order to reduce the electrical resistance for an electric machine that has windings arranged in grooves and can be operated with alternating current, the bundles (3) of the at least one strand are interchanged between the coils (1) in such a way that each bundle (3) of the at least one strand is arranged in the grooves at least n times and at most n' times at each of the possible bundle positions of the at least one strand in relation to the deepest possible bundle position in the groove, wherein n is the integer quotient in regard to the quotient of the number s of coils (1) of a strand connected in series and the number b of possible bundle positions of a strand, wherein n'=n if s is divisible by b and n'=n+1 if s is not divisible by b.