ELECTRICAL SYSTEMS

Electrical systems 201 for connecting rotary electric machines 111, 113 with gas turbine spools are provided. One such electrical system 201 comprises: a first rotary electric machine 111 mechanically coupled with a first gas turbine spool and a second rotary electric machine 113 mechanically coupled with a second gas turbine spool, each said electric machine 111, 113 having an identical even number N ≥ 4 of phases, each phase having a respective index n = (1,...,N), and each phase comprising an identical number P ≥ 1 of coils wound in a P-plex configuration in which adjacent phases are radially separated by 2π/NP mechanical radians; a first set 203 of N bidirectional converter circuits for conversion of alternating current (ac) to and from direct current (dc), each converter circuit having a respective index n and being connected with the P coils in the nth phase of the first rotary electric machine 111; and a second set 204 of N bidirectional converter circuits for conversion of ac to and from dc, each converter circuit having a respective index n and being connected with the P coils in the nth phase of the second rotary electric machine 113. For all n, a dc side of the nth converter circuit in said first set is connected with a dc side of the nth converter circuit in said second set to facilitate dc power transfer between the first gas turbine spool and the second gas turbine spool.