STATOR FOR AN ELECTRICAL MACHINE WITH IMPROVED PROTECTION AGAINST POTENTIAL DIFFERENCES BETWEEN ADJACENT STATOR COILS

Description

TECHNICAL FIELD

[0001] A stator for an electrical machine is specified, comprising an annular stator base body with a plurality of stator laminations arranged in a row and inwardly open stator slots, as well as stator coils of a stator winding arranged in the stator slots, which stator coils are assigned to a plurality of phases of the electrical machine. Furthermore, an electrical machine with a rotor is disclosed, which is mounted relative to a stator of the above-mentioned type so as to be rotatable about the rotational axis of the rotor. Furthermore, a drive arrangement with an electrical machine of the above-mentioned type and a power supply connected to the stator winding is specified, wherein the power supply is configured to supply electrical current to adjacent stator coils of the same phase that are electrically connected in parallel.Finally, a vehicle is provided with at least two axles, at least one of which is driven, said drive being provided at least partially or temporarily by the electric machine of the type mentioned above. STATE OF THE ART

[0002] A stator, an electric machine, a drive arrangement, and a vehicle of the above-mentioned type are generally known from the prior art. In particular, the power supply of the drive arrangement can be provided by an inverter, which supplies the electric machine with electrical energy from a battery or accumulator. Increasingly faster switching electronic switching elements (particularly transistors) lead to voltage pulses with very high edge steepness. Due to this high edge steepness, wave phenomena sometimes occur in the stator coils of the stator winding, in the sense that an edge of a voltage pulse propagating along the wires of adjacent stator coils connected in parallel can lead to a dangerous potential difference between the stator coils.This is particularly problematic at the end faces of the stator or at the winding head, as the wires can touch there, and the potential difference can cause damage to the stator coils. Prior art stators are described in documents WO2014 / 184951 A1, DE 10 2017 210 445 A1, US 2008 / 0238240 A1, and DE 103 31 841 A1. DISCLOSURE OF THE INVENTION

[0003] An object of the invention is therefore to provide an improved stator for an electric machine, an improved electric machine, an improved drive assembly, and an improved vehicle with such an electric machine. In particular, a potential difference between electrically parallel-connected and adjacent stator coils of the same phase is to be avoided, even during rapid voltage pulses.

[0004] The object of the invention is solved by the features of claim 1. Preferred developments are the subject of the dependent claims.

[0005] The proposed measures make it possible to overcome the disadvantages mentioned above. In particular, the potential difference between adjacent windings of the stator coils does not reach any significant values, even with voltage pulses with very high edge steepness. This is because these voltage pulses propagate in the same direction in adjacent stator coils, i.e., radially outwards or radially inwards, and an edge in both stator coils is at the same radial position at the same time. The risk of electrical flashover between the stator coils, particularly in the area at the end faces of the stator or at the winding overhang, is therefore low. A potential difference between electrically parallel-connected and adjacent stator coils of the same phase is therefore zero or almost zero at a specific radial position, even during fast transient events such as those that can occur in modern inverters.

[0006] Electrical conductors encompassed by adjacent stator coils of the same phase are each substantially helical and extend radially in the same direction from a connection point of the parallel circuit relative to a rotational axis of the stator base body. In other words, electrical conductors encompassed by adjacent stator coils of the same phase are each substantially helical, and a radial component of a longitudinal extension of the electrical conductors relative to a rotational axis of the stator base body is aligned in the same direction from a connection point of the parallel circuit.

[0007] Radially inner terminals and radially outer terminals of adjacent stator coils of the same phase can each be electrically connected to each other, in particular directly connected. The terminals of adjacent stator coils of the same phase can have a common or separate star points.

[0008] The above embodiments and further developments of the invention can be combined in any way. SHORT DESCRIPTION OF THE CHARACTERS

[0009] The present invention will be explained in more detail below with reference to the exemplary embodiment shown in the schematic figure of the drawing. It shows: Figure 1 shows a schematic half-section of an exemplary electrical machine; Figure 2 shows the stator base body of the electrical machine from Fig. 1 in front view; Figure 3 a section through the stator in detail; Figure 4 a schematic representation of a clockwise wound stator coil; Figure 5 a schematic representation of a counterclockwise wound stator coil; Figure 6 the stator coil from Fig. 4 in a technically common representation; Figure 7 the stator coils from Fig. 4 und 5 in a technically common representation; Figure 8 a circuit diagram of an exemplary stator of an electrical machine; Figure 9 the circuit diagram from Fig. 8 supplemented with symbolic representations of the stator coils and Figure 10 an electrical machine with a stator of the proposed type, which is installed in a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0010] By way of introduction, it should be noted that identical parts in the different embodiments are provided with the same reference symbols or component designations, possibly with different indices. The disclosures of a component contained in the description can be transferred mutatis mutandis to another component with the same reference symbol or component designation. Furthermore, the positional information chosen in the description, such as "top," "bottom," "rear," "front," "side," and so on, refer to the directly described and illustrated figure and, in the event of a change in position, are to be transferred mutatis mutandis to the new position.

[0011] Fig. 1 shows a half-section through a schematically illustrated electrical machine 1. The electrical machine 1 comprises a shaft 2 with a rotor 3 sitting thereon, wherein the shaft 2 is rotatably mounted about a rotation axis A relative to a stator 5 by means of (rolling) bearings 4a, 4b. The stator 5 in this example comprises a plurality of stator laminations 6, which form a stator lamination stack or a stator base body 7, as well as a stator winding 8 arranged therein. Specifically, the first bearing 4a is seated in a front bearing plate 9 and the second bearing 4b in a rear bearing plate 10. Furthermore, the electrical machine 1 comprises a (middle) housing part 11, which connects the front bearing plate 9 and the rear bearing plate 10 and also accommodates the stator base body 7. The front bearing plate 9, the rear bearing plate 10 and the housing part 11 thus form the housing 12 of the electrical machine 1 in this example.

[0012] Fig. 2 shows the stator base body 7 in front view, specifically without stator winding 8. Clearly visible are the radially inwardly open stator slots 13, which accommodate the stator winding 8, which comprises several stator coils. Fig. 2 There is also an area B marked, which is in the Fig. 3 is shown in an enlarged form. The stator slots 13 can run in particular in the axial direction or helically

[0013] Fig. 3 now shows the Fig. 2 The section of the marked area B, in this case with the stator coils 14a, 14b of the stator winding 8 arranged in the stator slots 13a, 13b. Each of the stator coils 14a, 14b has several turns 15a..15k, which are hatched differently for easier differentiation. Each of the turns 15a..15k in turn consists of several coil wires 16, in this specific case of ten coil wires 16. However, a different number of turns 15a..15k and coil wires 16 could also be provided.

[0014] In the Fig. 3 One half of the stator coils 14a, 14b is shown, specifically a right half of the stator coil 14a and a left half of the stator coil 14b. The stator coils 14a, 14b have different winding directions, as shown in the Fig. 4 und 5 is illustrated. The Fig. 4 The symbolically represented stator coil 14a is wound clockwise, which in Fig. 5 The symbolically represented stator coil 14b is counterclockwise. Accordingly, the coil wires are arranged - roughly speaking - along a left-handed or right-handed helix. Fig. 4 und 5 For the sake of clarity, only four windings 15a..15d are shown symbolically, each with a different line style.

[0015] Fig. 6 shows the stator coil 14a and its arrangement in the stator slots 13 in commonly used technical notation. Specifically, the stator coil 14a is depicted in the shape of a hexagon, and the stator slots 13 are numbered. The coil input SE and the coil output SA are also labeled.

[0016] Fig.7 shows the coil pair formed by the stator coils 14a and 14b in technically common notation. As can be seen from the Fig. 7 As can be seen, the stator coils 14a, 14b are electrically connected in parallel and occupy the stator slots 13 with the numbers "01", "02", "07" and "44". Accordingly, Fig. 3 The stator slot 13a is shown with the number "02" and the stator slot 13b with the number "01". Due to the parallel connection, the stator coils 14a, 14b are assigned to one phase L1 of several phases L1..L3 of the electrical machine 1 (see also Fig. 8 and 9 ).

[0017] The Fig. 8 shows an example winding diagram or circuit diagram of an eight-pole single-layer winding with 48 stator slots 13. The stator coils 14a, 14b are also numbered. Fig. 9 finally shows the winding diagram or circuit diagram from Fig. 8 supplemented with the symbolic windings 15a..15k.

[0018] A stator 5 for an electrical machine 1 is thus disclosed, comprising an annular stator base body 7 with inwardly open stator slots 13, 13a, 13b, as well as stator coils 14a, 14b arranged in the stator slots 13, 13a, 13b, which are assigned to several phases L1 to L3 of the electrical machine 1. Adjacent stator coils 14a, 14b of the same phase L1 are wound in opposite directions and electrically connected in parallel. In particular, the radially inner terminals of the stator coils 14a, 14b and the radially outer terminals of the stator coils 14a, 14b of the same phase L1 are each electrically connected to one another. A power supply connected to phase L1 therefore generates a current flow with a different winding sense in the stator coils 14a, 14b. In particular, as is the case here, all adjacent stator coils 14a, 14b of the same phase L1 or L2 or L3 are wound in opposite directions and electrically connected in parallel.

[0019] This results in the advantage that the potential difference between adjacent windings 15a..15k of the stator coils 14a, 14b does not assume any significant values, even with voltage pulses with very high edge steepness. The reason is that these voltage pulses propagate in the same direction in adjacent stator coils 14a, 14b, i.e., radially outward or radially inward, and an edge in both stator coils 14a, 14b is at the same radial position at the same time. The risk of electrical flashover between the stator coils 14a, 14b, especially in the area at the end faces of the stator 5 or at the winding overhang, is therefore low.

[0020] In the Fig. 3 For each stator winding 14a, 14b, a voltage-displacement diagram U / s or a voltage-time diagram U / t is shown. The diagram shows that an edge of a voltage pulse propagates radially outward from the coil input SE and that at a specific radial position at a specific time t, the same electrical voltage is present in both stator windings 14a, 14b. A potential difference ΔP at a specific radial position is zero or almost zero, even during fast transient events such as those that can occur in modern inverters.

[0021] The Fig. 10Finally, the electric machine 1 installed in a vehicle 17 is shown. The vehicle 17 has at least two axles, at least one of which is driven. Specifically, the electric motor 1 is connected to an optional transmission 18 and a differential gear 19. The half-axles 20 of the rear axle are connected to the differential gear 19. Finally, the driven wheels 21 are mounted on the half-axles 20. The vehicle 17 is driven at least partially or temporarily by the electric machine 1. This means that the electric machine 1 can serve solely to drive the vehicle 17 or, for example, can be provided in conjunction with an internal combustion engine (hybrid drive).

[0022] Finally, it is noted that the scope of protection is determined by the patent claims. However, the description and drawings must be used to interpret the claims. The features contained in the figures can be interchanged and combined with one another as desired. In particular, it is also noted that the devices depicted may in reality comprise more or fewer components than shown. In some cases, the depicted devices or their components may also be shown not to scale and / or enlarged and / or reduced in size.

Claims

1. Stator (5) for an electric machine (1), comprising an annular stator core (7) with multiple stator laminations (6) and stator slots (13, 13a, 13b) open toward the inside, as well as stator coils (14a, 14b) of a stator winding (8) arranged in the stator slots (13, 13a, 13b), which are assigned to multiple phases (L1...L3) of the electric machine (1), wherein adjacent stator coils (14a, 14b) of the same phase (L1...L3) are wound in opposite directions and are electrically connected in parallel, wherein electrical conductors (16), which are encompassed by the adjacent stator coils (14a, 14b), are each essentially helically (spirally) shaped and extend, starting from a connection point of the parallel connection, radially in the same direction with respect to a rotational axis (A) of the stator core (7).

2. Stator (5) according to claim 1, characterized in that the radially inner and radially outer terminals of the adjacent stator coils (14a, 14b) of the same phase (L1...L3) are electrically connected to each other, in particular directly connected to each other.

3. Stator (5) according to claim 2, characterized in that the terminals of the adjacent stator coils (14a, 14b) of the same phase (L1...L3) have a common or separate star point(s).

4. Electric machine (1) with a rotor (3) that is rotatably mounted relative to a stator (5) about the rotational axis (A) of the rotor (3), characterized in that the stator (5) is designed according to one of claims 1 to 3.

5. Drive assembly comprising an electric machine (1) according to claim 4 and a power supply connected to the stator winding (8), characterized in that the power supply is configured to generate a current flow in the oppositely wound and electrically parallel-connected adjacent stator coils (14a, 14b) of the same phase (L1...L3), with different winding direction.

6. Vehicle (17) with at least two axles, of which at least one is driven, characterized in that said drive is at least partially or temporarily provided by the electric machine (1) according to claim 5.