FIELD

The present application relates to a winding system for a stator of an electric machine and an electric machine.

BRIEF SUMMARY OF THE DISCLOSURE

The electric machine can comprise a stator and a rotor moveably mounted relative thereto. Electric machines can be operated as a motor or as a generator. The stator can comprise an electric winding in slots which is formed of an electrically conductive material and, for example, has the shape of bars. The electric winding is connected to a power supply unit, which can be multi-phase. A separate switch or a separate half-bridge is required for each phase. As many switches or half-bridges as slots are required in the case where each slot has its own phase.

The distribution of the magnetomotive force of a rotating field generated by the stator depends on the number of slots or the number of phases. The more slots or phases the stator comprises, the more the distribution of the magnetomotive force approaches the shape of a sinusoidal function. The quality of the rotating field can thus be increased by increasing the number of slots or phases. However, this also increases the number of half-bridges, thus leading to an increased complexity of the winding system and to higher costs.

An object to be solved is to provide an efficient winding system for a stator of an electric machine. A further object to be solved is to specify an electric machine which can be operated efficiently.

The objects are achieved by the subject matter of the independent patent claim and a dependent claim. Advantageous embodiments and further developments are specified in the subclaims.

According to at least one embodiment of the winding system for a stator of an electric machine, the winding system comprises at least two first conductor segments and at least two second conductor segments. The first and second conductor segments can comprise an electrically conductive material such as copper or aluminum. The stator can, for example, comprise slots, in each of which a conductor segment is located. The stator can comprise one or more stator laminations in which the slots are introduced. Preferably, the stator comprises a plurality of slots. The first and second conductor segments can, for example, be electrically conductive bars.

The winding system further comprises at least two half-bridges, wherein each half-bridge is connected to at least one first conductor segment and one second conductor segment. The half-bridges can be connected to a power supply unit and be set up to provide its own phase current. The half-bridges can, for example, be bipolar electronic switches, such as metal oxide semiconductor field effect transistors (MOSFET) or bipolar transistors (IGBT). Each half-bridge is associated with at least one pair of a first conductor segment and a second conductor segment, so that each half-bridge is electrically connected to at least one first conductor segment and one second conductor segment.

The winding system further comprises at least one first short-circuit means and at least one second short-circuit means, wherein each first conductor segment is connected to the first short-circuit means and each second conductor segment is connected to the second short-circuit means. The first conductor segments are electrically conductively connected to each other on a first side of the stator via the first short-circuit means. In addition, the second conductor segments are electrically conductively connected to each other on the first side of the stator via the second short-circuit means. The first conductor segments are thus connected to each other on the first side of the stator in such a way that they form a short-circuit. Further, the second conductor segments are connected to each other on the first side of the stator so as to form a short-circuit. The conductor segments are connected to the half-bridges on a second side of the stator facing away from the first side.

The winding system preferably comprises a plurality of first and second conductor segments. The first and the second conductor segments can be disposed alternately to each other. That is, if the conductor segments are disposed, for example, around the circumference of the stator, a second conductor segment is disposed in both directions along with a first conductor segment along the circumference, respectively. Likewise, two first conductor segments are disposed along with each second conductor segment, wherein a first conductor segment is disposed along the circumference in one direction along with the second conductor segment and a further first conductor segment is disposed along the circumference in the opposite direction along with the second conductor segment. Pairs of conductor segments can thus be disposed along the circumference of the stator, which pairs each comprise one first and one second conductor segment. Each pair of two conductor segments is associated with a half-bridge which is connected to the first conductor segment and the second conductor segment. The half-bridges can be set up to respectively supply the first and second conductor segments of a pair with a phase current.

The winding system can be configured to generate a time-varying rotating field having a set number of poles. If a rotor of the electric machine can interact with the number of pole pairs of the rotating field, then the rotor can be driven by a torque generated by the rotating field. For a winding system comprising only one short-circuit means, as many half-bridges as conductor segments of the winding system are required. However, it has been shown that a winding system comprising at least two short-circuit means and half as many half-bridges as conductor segments can generate a rotating field similar to a winding system having only one short-circuit means. Advantageously, fewer half-bridges are thus required for the winding system described here. If the winding system comprises exactly two short-circuit means, then half as many half-bridges as conductor segments are required. If the winding system comprises more than two short-circuit means, one half-bridge per number of short-circuit means is respectively required.

Since the quality of the rotating field for a winding system having one short-circuit means is similar to the quality of the rotating field of a winding system described here, fewer half-bridges are required for approximately constant quality. The complexity and cost of the winding system can thus be reduced. The winding system is therefore more efficient.

According to at least one embodiment of the winding system, the conductor segments each comprise a single conductor or in each case a plurality of conductor filaments disposed parallel to each other and electrically connected in parallel. The conductor segments can thus each comprise a single electrically conductive wire or bar or be formed using one or more electrically conductive materials. It is also possible for the conductor segments to each comprise a plurality of electrically conductive wires, bars or conductor filaments which are disposed parallel to each other. It is also possible for some conductor segments to each comprise a single conductor and that other conductor segments each comprise a plurality of conductor filaments disposed parallel to each other and electrically connected in parallel. Each conductor segment can thus be supplied with its own electric phase, so that the stator can generate a rotating field. In addition, the production of the stator is simplified if the conductor segments each comprise a single conductor or a plurality of conductor filaments disposed parallel to each other and electrically connected in parallel.

According to at least one embodiment of the winding system, the conductor segments are designed rectilinear and disposed parallel to each other. For example, each conductor segment has the shape of a bar. The stator can thus be constructed similar to a cage rotor, wherein the short-circuit means are attached only on the first side of the stator. The manufacture of the bars and the slots is simplified since the conductor segments are designed rectilinear.

According to at least one embodiment of the winding system, the conductor segments are distributed along a circumference of the stator. For example, if the stator has the shape of a cylinder, the conductor segments can extend in the direction of the longitudinal axis of the cylinder. The conductor segments are disposed next to each other along the circumference of the stator. For example, the conductor segments can have the same radial distance to a center of the stator. Preferably, the conductor segments are disposed equidistant from each other. Since the conductor segments are distributed along the circumference of the stator, the stator can generate a rotating field during operation of the electric machine. The rotating field can drive a rotor during operation of the electric machine, which rotor can be disposed as an internal rotor or as an external rotor.

According to at least one embodiment of the winding system, the number of conductor segments which are connected to the same half-bridge corresponds to the number of short-circuit means of the winding system. This means that if the winding system comprises two short-circuit means, the winding system also comprises at least two first conductor segments both connected to the first short-circuit means, and the winding system comprises at least two second conductor segments both connected to the second short-circuit means. Exactly one first conductor segment and one second conductor segment are thus always connected to the same half-bridge. If the winding system comprises a larger number of short-circuit means, then the number of short-circuit means corresponds to the number of conductor segments which are connected to one and the same half-bridge. In total, fewer half-bridges are thus required than for the case where each half-bridge is connected to only one conductor segment. The complexity and cost of the winding system can thus be reduced.

According to at least one embodiment of the winding system, the winding system comprises at least one third conductor segment and at least one third short-circuit means, wherein each third conductor segment is connected to the third short-circuit means. Each half-bridge is thus connected to one first conductor segment, one second conductor segment and one third conductor segment. It has been shown that even with a winding system having a third short-circuit means, a magnetomotive force similar to that of a winding system having only one short-circuit means can be generated. Since only one third of the number of half-bridges are required in a winding system having three short-circuit means compared with a winding system having one short-circuit means, the complexity and cost of a winding system having three short-circuit means are reduced.

According to at least one embodiment of the winding system, the at least two half-bridges are connected to a power supply unit. The at least two half-bridges are connected to a power supply unit to supply the winding system with phase currents. For example, the power supply unit can be a DC source. In this case, the half-bridges can comprise two switches, which are alternately opened and closed, so that an AC voltage is applied to the conductor segments which are connected to the half-bridges. Since an AC voltage is applied to the conductor segments, the stator can generate a rotating field with the winding system.

According to at least one embodiment of the winding system, each of the at least two half-bridges is set up to provide its own phase current. Each of the half-bridges is thus set up to generate its own phase current. Since each of the half-bridges is connected to at least two conductor segments, the phase current of the respective half-bridge is divided between the respectively connected conductor segments. The phase currents of the winding system can generate a rotating field.

According to at least one embodiment of the winding system, the phase currents are out of phase with each other. This means that the phase currents are temporally offset from each other or phase-shifted in time. The phase currents of the winding system thus generate a rotating field, which is time-varying, so that a torque can be generated in a rotor of the electric machine, in the case where the rotor interacts with the number of pole pairs of the stator.

According to at least one embodiment of the winding system, the short-circuit means are disposed radially along a cross-section through the stator. If the short-circuit means have, for example, the shape of a circle, then the diameter of the first short-circuit means can be greater than the diameter of the second short-circuit means, or vice versa. Along a cross-section through the stator, the short-circuit means are then disposed at the same position along the longitudinal axis of the stator and at different radial positions. Preferably, the short-circuit means are not disposed in direct contact and are electrically isolated from each other. It is thus not necessary to design the stator longer along the longitudinal axis to dispose at least two short-circuit means.

According to at least one embodiment of the winding system, the short-circuit means are disposed at different positions along an axis of rotation of the stator. The axis of rotation can be, for example, a longitudinal axis of the stator. The short-circuit means can further have different diameters. The short-circuit means are offset from each other along the axis of rotation of the stator.

Further, an electric machine is specified. According to at least one embodiment of the electric machine, the electric machine comprises a stator with a winding system as described here. Thus, all features of the described winding system are also disclosed for the winding system of the electric machine and vice versa. The electric machine further comprises a rotor rotatably mounted to the stator. The rotor can be formed, for example, by a cage rotor, a rotor having permanent magnets, a externally excited synchronous rotor, a rotor for a switched reluctance machine, or a rotor for a synchronous reluctance motor. The rotor can be an internal rotor or an external rotor. An air gap can be disposed between the stator and the rotor.

If the rotor of the electric machine can interact with the number of pole pairs of the stator, then the rotor can be driven by the rotating field generated by the stator.

Since the winding system of the stator of the electric machine comprises at least two short-circuit means and each of the half-bridges is connected to at least one first conductor segment and one second conductor segment, the complexity and the cost of the electric machine are reduced. The electric machine can thus be operated more efficiently.

According to at least one embodiment of the electric machine, the stator is designed to generate at least one rotating field in which the number of pole pairs is variable. Each of the at least two half-bridges of the winding system can be set up to provide its own phase current. Each of the at least two half-bridges can also be set up to provide different phase currents. This means that the phase currents provided by the half-bridges can be changed so that the rotating field generated by the stator can comprise different numbers of pole pairs. The number of poles of the rotating field generated by the stator depends on the phase currents provided by the half-bridges. Changing the phase currents can thus change the number of poles of the rotating field generated by the stator.

Advantageously, in the electric machine, the number of pole pairs of the rotating field generated by the stator can be changed without changing the structure of the electric machine. It is thus also possible to change the number of pole pairs when operating the electric machine.

According to at least one embodiment of the electric machine, the stator comprises a plurality of slots, wherein exactly one conductor segment of the winding system is placed per slot. The conductor segments can, for example, have the shape of a rectilinear bar. The production of the stator is thus simplified because of the rectilinear shape of the conductor segments and the slots.

The winding system described here and the electric machine are explained in more detail in the following in connection with embodiments and the associated figures.

