Electrical machine comprising a temperature sensor integrated into the rotor

Abstract

The present invention relates to an electrical machine comprising a stator, a rotor (1) with salient poles, a rotating shaft on which the rotor (1) is mounted, and a temperature sensor (80), the electrical machine being characterized in that the temperature sensor (80) is arranged between a rotor winding and a rotor body (2).

Description

Description Title of the invention: Electrical machine comprising a temperature sensor integrated into the rotor

[0001] The present invention relates to the field of electrical engineering, and more specifically concerns an electrical machine comprising a salient pole rotor.

[0002] In such an electric machine, the rotor has a winding around each of its salient poles. In applications requiring significant power from the electric machine, particularly when used in an electric or hybrid vehicle, it is necessary to monitor the temperature of the rotor windings to prevent overheating, which could destroy the insulating enamel on the winding wires and cause short circuits in the rotor.

[0003] To avoid this situation, which arises when the winding temperature reaches a critical threshold, salient-pole rotor electric machines typically incorporate a winding temperature control system that prevents the temperature from reaching this critical threshold. Specifically, in such a machine, a performance limitation process is implemented as soon as the winding temperature reaches a safety margin below this critical threshold. This aims to allow the winding temperature to drop sufficiently quickly, without the windings having time to reach the critical temperature due to the latency of this performance limitation. For example, the motor torque of the electric machine is limited as soon as the rotor winding temperature is 10 degrees Celsius below the critical temperature threshold.

[0004] This safety margin is all the more important given the difficulty in accurately estimating the rotor winding temperature. Consequently, the torque demanded by the driver of an electric vehicle powered by such a machine is limited too quickly once the machine has delivered maximum power for an extended period. The vehicle's performance and driving experience are therefore directly impacted by the inaccuracy of the rotor temperature estimation.

[0005] Indeed, currently, the rotor temperature is often estimated from a thermal model using a temperature measurement at the stator, or from a model using on the one hand a rotor resistance calculated from measurements or estimates of stator or rotor currents, speeds and fluxes, and on the other hand a reference resistance measured during tests carried out at the end of the rotor manufacturing line, as for example in document FR3033961.

[0006] However, by using values ​​measured or estimated at the end of the manufacturing chain, Such as thermal resistances or a reference resistance, these methods provide an estimate of the rotor temperature that deviates over time from the actual rotor temperature, or from the temperature of a machine with manufacturing defects. For example, these resistances will differ between a reference machine and a machine with non-compliant hot-crimped connections, connections that have deteriorated over time, or a broken winding. These differences between the estimated and actual rotor temperature explain the application of a safety margin in the implementation of performance limitations for the electric machine, a margin that is larger than what would be required with a real-time measurement of the rotor temperature.

[0007] The present invention remedies at least in part the drawbacks of the prior art, by providing an electrical machine whose rotor temperature is measured directly on the rotor.

[0008] To this end, the invention proposes an electrical machine comprising a stator, a salient pole rotor, a rotating shaft on which the rotor is mounted, and a temperature sensor, the electrical machine being characterized in that the temperature sensor is arranged between a winding of the rotor and a body of the rotor.

[0009] By mounting a temperature sensor directly on the rotor, rather than on the stator, the safety margin applied relative to a critical rotor temperature threshold that would otherwise limit machine performance can be reduced. This arrangement between the rotor winding and the rotor body allows for precise temperature measurement of the windings, which would not be possible by positioning the temperature sensor in unobstructed locations on the rotor, such as between winding spacers and the rotor body.

[0010] In one embodiment of the invention, the temperature sensor includes a thermistor. This type of temperature sensor has the advantage of being very precise and economical. Examples include an NTC (for "negative temperature coefficient") or PTC (for "positive temperature coefficient") temperature sensor.

[0011] According to an advantageous feature of the electric machine according to the invention, the rotor body comprises a central portion and a plurality of teeth distributed angularly around the central portion, at least one tooth extending parallel to the axis of the rotating shaft from a first axial end of the body to a second axial end of the body, and extending radially from the central portion to a pole head. The electric machine further comprises at least one coil head guide flanked on the first or second axial end of the body and comprising at least one arm arranged on an axial end of the tooth. The rotor winding surrounds the tooth and the arm of the coil head guide. temperature being housed in the branch of the coil head guide.

[0012] The individual teeth of the rotor body are preferably identical. The electric machine according to the invention includes, for example, a coil head guide at each axial end of the rotor body. The coil head guide preferably has as many arms as there are teeth on the rotor body, each arm flanking one axial end of one of these teeth. Preferably, a single coil head guide has one arm housing the temperature sensor. The rotor preferably includes one or more temperature sensors, each located in one or more arms of the coil head guide. Thus, two sensors on two different arms ensure safe redundancy.

[0013] Advantageously, the branch comprises a portion entirely covered by the winding, the portion having a housing extending radially between the central part and the pole head, into which the temperature sensor is inserted. For example, the radial dimension of the housing represents at least 80% of the radial dimension of the winding.

[0014] Since the temperature of the winding wires varies along the radial dimension of the winding, this arrangement allows the temperature sensor to obtain a representative temperature reading of the entire winding by covering the whole housing. This is because the wires in the center of the winding are generally hotter than the wires on the periphery.

[0015] Advantageously, the thickness of the branch within the housing allows the temperature sensor to make contact with the winding along the entire radial dimension of the housing. This makes the temperature measurement even more representative of the winding temperature. The branch thickness within the housing corresponds to the axial dimension of the branch between the rotor body and the temperature sensor. The housing is therefore generally not a through-branch. By not being in direct contact with the rotor body, the temperature sensor is not affected by heat radiating from the rotor body, as the coil head guides are generally made of insulating material.

[0016] In an alternative embodiment, the housing is arranged in a branch head opposite the winding. In this embodiment, the temperature sensor is preferably in contact with the entire axial thickness of the winding on the branch.

[0017] In one embodiment of the invention, the arm includes a passage between the housing and a central space in the coil head guide, the passage being suitable for housing the connection wires of the temperature sensor. These connection wires supply power to the temperature sensor. The temperature sensor is, for example, powered by a power supply battery located in the central space in the coil head guide.

[0018] Advantageously, the connecting wires are linked to a power supply and temperature sensor control unit located in the central space of the coil head guide. This arrangement allows easy access for maintenance of the unit. Preferably, the temperature sensor includes wireless communication means with a rotor control unit. The rotor control unit is located in a non-rotating part of the electric machine or of a vehicle incorporating this electric machine.

[0019] The invention also relates to an electric or hybrid vehicle comprising an electric machine according to the invention.

[0020] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which:

[0021] [Fig. 1] partially represents an electrical machine according to the invention, at the level of a branch of a coil head guide, the branch having a housing for a temperature sensor, and

[0022] [Fig.2] also partially represents the electrical machine of [Fig.1], in which the temperature sensor is arranged in the housing.

[0023] According to one embodiment of the invention, an electrical machine according to the invention illustrated [Fig.1] comprises a stator and a wound rotor 1 mounted on a rotating shaft (not shown).

[0024] The rotor 1 comprises a rotor body 2, made of magnetic steel, for example formed by a stack of sheets around the rotating shaft. The rotor body 2 comprises a central part 22 fixed to the rotating shaft, on which teeth 24, formed from the material of the central part 22, are distributed angularly.

[0025] The rotating shaft is capable of rotating about an axis parallel to an axial direction referenced X in [Fig. 1]. The axis of the rotating shaft also defines a radial direction, orthogonal to the axial direction and passing through the axis of the rotating shaft. Thus, in [Fig. 1], the tooth 24 extends radially along a radial direction R, from the central part 22 of the rotor body 2 to a pole head 26. Finally, an angular direction is defined as being orthogonal to the axial and radial directions.

[0026] The tooth 24 extends axially from a first axial end of the rotor body 2 to a second axial end of the rotor body 2, and radially from a base 28 of the proximal tooth to the central portion 22, to the pole head 26, which is part of the tooth 24. The portion of the tooth 24 located between the base 28 of the tooth and the pole head 26 is intended to accommodate one of the rotor windings (not shown). An electrical insulator 50, for example paper, surrounds this portion of the tooth along its entire radial and axial dimensions. The rotor winding is designed to fill, in particular, the space 30 located between the electrical insulator 50 and another electrical insulator 52 situated between the tooth 24 and an adjacent tooth. This other insulator, for example made of paper, is folded into a V-shape to accommodate a triangular-section winding spacer 40 (visible [Fig. 2]), which holds the winding wires in place between the rotor body teeth despite the centrifugal force during the operation of the electric machine. The rotor winding also fills, symmetrically with respect to a radial plane passing through the middle of the tooth 24 and the axis of the rotating shaft, a space located between the electrical insulator 50 and yet another electrical insulator 54 situated between the tooth 24 and the adjacent tooth on the rotor body 2.Similarly, a winding spacer 42, of triangular section, holds in place the winding wires located between tooth 24 and that other adjacent tooth.

[0027] In this embodiment of the invention, the rotor body 2 has eight teeth and is very similar to the rotor body shown in Figure 6 of document FR3084220. In that document, each axial end of the rotor body is flanked by an eight-pronged coil head guide. In the embodiment of the invention described in this application, the rotor body 2 is also flanked by two coil head guides.

[0028] Figure 1 shows the first axial end of the rotor body 2, to which a coil head guide 60 is attached. On this first axial end of the rotor body 2, the coil head guide 60 has a central ring attached to the central portion 22 of the rotor body 2, and a plurality of arms extending radially over each axial end of the teeth of the rotor body 2. The coil head guide 60 is made of an electrically insulating material, at least in the areas where it contacts the rotor windings. For example, the coil head guide 60 is made of a synthetic polymer (plastic).

[0029] The coil head guide 60 includes, in particular, a branch 62 pressed against the axial end of the tooth 24 corresponding to the first axial end of the rotor body 2. More precisely, the branch 62 is pressed against the electrical insulator 50 at the part thereof located on the axial end of the tooth 24.

[0030] The arm 62 comprises a arm head 64, flanked against the pole head 26 of the tooth 24, and a portion 66 situated between the central ring of the coil head guide 60 and the arm head 64. This portion 66 is intended to be entirely covered by the wires of the rotor winding surrounding the tooth 24. The portion 66 has rounded sides on which grooves 68, each arranged angularly, accommodate a wire from a first layer of the rotor winding, this first layer being proximal to the tooth 24. The set of grooves 68 on Each side of section 66 completely covers the radial dimension of that side. In this way, the winding wires are guided during their installation so as to completely cover section 66 of branch 62. The branch head 64 is designed to radially hold the winding wires, which pass angularly over this section 66 of branch 62, despite the centrifugal force. This branch head 64 therefore forms an axial extension of the pole head 26, with an axial dimension larger than that of section 66 of branch 62.

[0031] In this embodiment of the invention, the branch 62 includes a housing 70 for a temperature sensor 80 (visible [Fig. 2]). This housing 70 is through-hole, revealing the electrical insulator 50 in [Fig. 1]. In an alternative embodiment of the invention, this housing is not through-hole.

[0032] The housing 70 here takes the form of a rectangular cavity situated between the rounded sides of the portion 66 and extending radially over almost the entire radial dimension of this portion 66, for example, 90% of this radial dimension. Since the temperature sensor 80 is, in this embodiment of the invention, an NTC or PTC type thermistor, the material forming this thermistor encloses the temperature sensor 80 and is therefore in contact with the rotor winding wires over the entire radial dimension of the housing 70, which it completely occupies. Indeed, the depth, in the axial dimension, of the housing 70 is such that the temperature sensor 80 is in contact with the rotor winding when the tooth 24 is wound.

[0033] In an alternative embodiment with a non-through housing, the thickness of the arm 62 at the housing is such that the temperature sensor 80 is in contact with the rotor winding when the tooth 24 is wound. This thickness corresponds to the axial dimension of the portion 66 between a flat surface of the arm, intended to be in contact with the electrical insulator 50 or the rotor body 2, and a receiving surface of the temperature sensor in the housing, parallel to this flat surface.

[0034] The branch 62 also includes a passage 72 between the housing 70 and a central space of the coil head guide 60, this passage 72 passing through the central ring of the coil head guide 60. This passage 72 allows connecting wires 82 from the temperature sensor 80 to be brought to a central space of the coil head guide 60, to connect them to a power supply and management device for the temperature sensor 80.

[0035] This power supply and management system includes, for example, a battery. Thanks to this design, it is not necessary to unwind the rotor windings to replace the battery.

[0036] The power supply and management device for the temperature sensor 80, located in the central space of the coil head guide 60, also includes an analog and / or software circuit for transmitting to a rotor control device 1, located in a non-rotating part of the electric machine, or to an external computer. to the electric machine, a representative value of the temperature of the rotor 1. This representative value is for example a resistance value of the thermistor of the temperature sensor 80, the power supply and management device including an Ohmmeter, or directly a temperature value.

[0037] The transmission of this value representing the temperature of rotor 1 to the control device of rotor 1 is done for example by wireless communication, using Bluetooth® or Zigbee® technology using the IEEE 802.15.4 standard.

[0038] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.

Claims

Claims

1. An electrical machine comprising a stator, a rotor (1) with salient poles, a rotating shaft on which the rotor (1) is mounted, and a temperature sensor (80), the electrical machine being characterized in that the temperature sensor (80) is arranged between a winding of the rotor and a body (2) of the rotor.

2. An electrical machine according to claim 1, wherein the temperature sensor (80) comprises a thermistor.

3. An electrical machine according to claim 1 or 2, wherein the body (2) of the rotor comprises a central portion (22) and a plurality of teeth (24) distributed angularly around the central portion (22), at least one tooth (24) extending parallel to the axis of the rotating shaft from a first axial end of the body to a second axial end of the body (2), and extending radially from the central portion (22) to a pole head (26), the electrical machine further comprising at least one coil head guide (60) flanked on the first or second axial end of the body (2) and comprising at least one branch (62) arranged on an axial end of the tooth (24), the rotor winding surrounding the tooth (24) and the branch (62) of the coil head guide (60), the temperature sensor (80) being housed in the branch (62) of the coil head guide (60).

4. Electrical machine according to claim 3, in which the branch (62) comprises a portion (66) entirely covered with the winding, the portion (66) comprising a housing (70) extending radially between the central part (22) and the pole head (26) and in which the temperature sensor (80) is inserted.

5. An electrical machine according to claim 4, wherein the radial dimension of the housing (70) represents at least 80% of the radial dimension of the winding.

6. An electrical machine according to claim 3 or 4, wherein a thickness of the branch (62) in the housing (70) is capable of bringing the temperature sensor (80) into contact with the winding over the entire radial dimension of the housing (70).

7. An electrical machine according to any one of claims 4 to 6, wherein the branch (62) comprises a passage (72) between the housing (70) and a space central to the coil head guide, the passage (72) being capable of housing connection wires (82) of the temperature sensor. temperature (80).

8. Electrical machine according to claim 7, in which the connection wires (82) are connected to a device for supplying and managing the temperature sensor (80) arranged in the space central to the coil head guide.

9. An electrical machine according to any one of claims 1 to 8, wherein the temperature sensor (80) comprises means for wireless communication with a rotor control device (1).

10. Electric or hybrid vehicle comprising an electric machine according to any one of claims 1 to 9.

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