A three-phase alternating current electric motor wherein when a number of pole pairs of a rotor is P and a number of slots in which stator windings are inserted is N, N/(6P) becomes an irreducible fraction with a value of a denominator of 4 or more and wherein the relation of N>3P stands, in which the motor, for the layout of one layer of windings arranged in the slots, the UVW three-phases are arranged so as to have rotational symmetry of ±120 degrees in terms of mechanical angle from each other and, for the layout of the second layer, the windings are arranged reversed in direction by 180 degrees in electrical angle from the phases of the first layer of windings which have rotational symmetry and offset by M number of slots from the first layer, where T is a particular odd number for the relationship of 4/35≦|T−2PM/N|≦ 8/35 is given.

The present invention relates to a method for increasing the efficiency of an energy transfer device (100) with which electrical energy is converted contactlessly into electrical energy with the aid of a magnetic field in order to electrically excite a rotor of an electrical machine, comprising the step of:

arranging an additional electrically conductive material layer (13) on at least one active part (12, 19, 35, 45) of the energy transfer device (100), wherein an active part of the energy transfer device (100) is a part of the energy transfer device (100) which is at least partially exposed to the magnetic field used for energy transfer, and wherein the electrical conductivity of the additional material layer (13) is greater than the electrical conductivity of the at least one active part (12, 19, 35, 45). Moreover, the invention relates to an energy transfer device (100) and to a use of an electrically conductive material.

A stator core including field slots housing field windings and armature slots housing armature windings is provided. Permanent magnets are housed in the respective armature slots. Field windings face to the permanent magnets directly or via the stator core on the outer and inner circumferential sides. A coil end of one of the armature windings straddles the predetermined one of the field slots and passes over the axial end face of each of the permanent magnets in the corresponding one of the field slots over which the coil end straddles.

A field coil type rotating electric machine includes a field coil having a serially-connected coil section pair consisting of first and second coil sections, a diode having its cathode and anode respectively connected to opposite ends of the serially-connected coil section pair, a rotating shaft, and a rotor having main pole portions radially protruding from a rotor core. In the rotating electric machine, there are formed both a series resonance circuit including the first coil section and at least one capacitor and a parallel resonance circuit including the second coil section and the at least one capacitor. Electronic components electrically connected with the field coil, which include the diode and the at least one capacitor, are arranged so that an overall center of gravity of all the electronic components is located closer than each of centers of gravity of the electronic components to a central axis of the rotating shaft.

A field coil type rotating electric machine includes a field coil having a serially-connected coil section pair consisting of first and second coil sections, a diode having its cathode and anode respectively connected to opposite ends of the serially-connected coil section pair, a rotating shaft, and a rotor having main pole portions radially protruding from a rotor core. In the rotating electric machine, there are formed both a series resonance circuit including the first coil section and at least one capacitor and a parallel resonance circuit including the second coil section and the at least one capacitor. Electronic components electrically connected with the field coil, which include the diode and the at least one capacitor, are arranged so that an overall center of gravity of all the electronic components is located closer than each of centers of gravity of the electronic components to a central axis of the rotating shaft.

An externally excited electric machine may comprise a stator, a rotor, a primary winding, a secondary winding, and electronics. The rotor may be arranged coaxially to and/or in the stator. The rotor may be rotatable relative to the stator about a rotation axis running in an axial direction. The rotor may have a magnetizable hollow-cylindrical core. The primary winding may be guided axially through the core. An electric primary current may flow through the primary winding. The secondary winding may be wound around the core so that an electric secondary current is induced via the primary winding in the secondary winding. The electronic may be connect to the secondary winding for tapping the secondary current.

An externally excited electric machine may comprise a stator, a rotor, a primary winding, a secondary winding, and electronics. The rotor may be arranged coaxially to and/or in the stator. The rotor may be rotatable relative to the stator about a rotation axis running in an axial direction. The rotor may have a magnetizable hollow-cylindrical core. The primary winding may be guided axially through the core. An electric primary current may flow through the primary winding. The secondary winding may be wound around the core so that an electric secondary current is induced via the primary winding in the secondary winding. The electronic may be connect to the secondary winding for tapping the secondary current.

An electric machine (21) having a stator (20) and having a rotor (29) rotatably mounted to the stator (20) is specified. The stator (20) comprises a stator winding (24), at least three teeth (23), and at least three grooves (22). In each case, one tooth (23) of the stator (20) is arranged between two grooves (22) along a circumference of the stator (20), and the stator winding (24) has at least three coils (25), wherein each of the coils (25) is wound around a tooth (23) of the stator (20), so that the stator winding (24) is a concentrated winding. In addition, the winding direction of all coils (25) is the same, each of the coils (25) is designed to be fed with its own phase current, and the stator (20) is designed to generate at least two rotary fields having different numbers of pole pairs independently of each other, in particular simultaneously. In addition, an activation unit (40) for the electric machine (21) and a method for operating an electric machine (21) are specified.

An electric machine (21) having a stator (20) and having a rotor (29) rotatably mounted to the stator (20) is specified. The stator (20) comprises a stator winding (24), at least three teeth (23), and at least three grooves (22). In each case, one tooth (23) of the stator (20) is arranged between two grooves (22) along a circumference of the stator (20), and the stator winding (24) has at least three coils (25), wherein each of the coils (25) is wound around a tooth (23) of the stator (20), so that the stator winding (24) is a concentrated winding. In addition, the winding direction of all coils (25) is the same, each of the coils (25) is designed to be fed with its own phase current, and the stator (20) is designed to generate at least two rotary fields having different numbers of pole pairs independently of each other, in particular simultaneously. In addition, an activation unit (40) for the electric machine (21) and a method for operating an electric machine (21) are specified.

A solid-state electromagnetic rotor, including a plurality of salient pole pieces arranged around a supporting structure, wherein a first end of each salient pole piece is attached to the support structure and a second end of each salient pole piece points outward away from the supporting structure. The wires wound around each salient pole piece, wherein when the wires of the plurality of salient pole pieces are sequentially excited by an excitation circuit. The salient pole pieces are energized to provide a moving polar magnetic field in the form of distinct magnetic poles as desired to accomplish power generation.