A temperature sensor arrangement

Abstract

A temperature sensor arrangement 200 for measuring a temperature of a stator assembly located in a stator cavity of an electric traction motor is disclosed. The temperature sensor arrangement comprises one or more temperature sensors 210, 212 and a sensor mounting bracket 204 for mounting the temperature sensors to the stator assembly. The sensor mounting bracket 204 comprises a sensor mount 206 coupled to the temperature sensors and a heat-transfer portion 208 extending from the sensor mount 206 and in thermal contact with the sensor mount, wherein the heat-transfer portion 208 is configured to transfer heat from the stator assembly to the sensor mount, and the temperature sensor is configured to measure a temperature of the sensor mount.

Description

TECHNICAL FIELD The present disclosure relates to a temperature sensor arrangement. Aspects of the invention relate to an electric traction motor and to a vehicle. BACKGROUND It is known to provide electrical drive units (EDUs) in vehicles, for example in Battery Electric Vehicles (BEVs). The EDU provides the drive to propel the vehicle forward. In order to provide electrical power to the EDU the EDU is typically connected to a traction battery. The electrical connection between the stator and the inverter of the electrical drive unit is typically provided using an inverter busbar. In prior systems the inverter busbars are provided in fixed positions and the corresponding stator busbars are welded to the electrical winding interface of the stator. As a result, the individual busbars may be able to move relative to each other in use. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a temperature sensor arrangement, an electric traction motor and a vehicle, as claimed in the appended claims. According to an aspect of the present teachings, there is provided a sensor mounting bracket for mounting a temperature sensor to a stator assembly located in a stator cavity of an electric traction motor, the sensor mounting bracket comprising: a sensor mount coupled to the temperature sensor; and a heat-transfer portion extending from the sensor mount and in thermal contact with the sensor mount; wherein the heat-transfer portion is configured to transfer heat from the stator assembly to the sensor mount, wherein the temperature sensor is configured to measure a temperature of the sensor mount. Advantageously, the thermal contact between the heat-transfer portion and the sensor mount enables the at least one temperature sensor to accurately measure the temperature of the stator assembly via the temperature sensor mounting bracket, for example from a location remote from the stator assembly. According to another aspect of the present teachings, there is provided a temperature sensor arrangement for measuring a temperature of a stator assembly located in a stator cavity of an electric traction motor, the temperature sensor arrangement comprising: a temperature sensor; and a sensor mounting bracket for mounting the temperature sensor to the stator assembly, wherein the sensor mounting bracket comprises: a sensor mount coupled to the temperature sensor; and a heat-transfer portion extending from the sensor mount and in thermal contact with the sensor mount, wherein the heat-transfer portion is configured to transfer heat from the stator assembly to the sensor mount, wherein the temperature sensor is configured to measure a temperature of the sensor mount. Advantageously, the thermal contact between the heat-transfer portion and the sensor mount enables the at least one temperature sensor to accurately measure the temperature of the stator assembly via the temperature sensor mounting bracket, for example from a location remote from the stator assembly. Optionally, the sensor mount is in thermal contact with both the temperature sensor and the heat-transfer portion such that, in use, the heat-transfer portion is arranged to transfer heat of the stator assembly to the temperature sensor, so as to enable the temperature sensor to indirectly measure a temperature of the stator assembly. Optionally, the heat-transfer portion comprises a planar contact surface arranged to contact the stator assembly at a planar interface. Advantageously, the planar contact surface enables the heat-transfer portion to form a planar contact interface with an adjacent flat portion of the stator assembly. Advantageously, a planar contact surface has a large surface area to volume ratio, thereby increasing heat transfer from the stator assembly to the sensor mount. A planar contact interface helps to increase the thermal contact area and is space efficient, thereby improving compactness of assembly of the temperature sensor arrangement to the stator assembly. The planar contact surface can also enable the sensor mounting bracket to be sandwiched between two flat surfaces of the stator assembly to improve heat transfer and / or ensure secure fixation of the sensor mount. Optionally, the heat-transfer portion comprises a fixing feature for fixedly mounting the sensor mounting bracket to the stator assembly. Advantageously, providing the fixing feature on the heat-transfer portion enables the heat-transfer portion to perform the dual function of fixing the sensor mounting bracket to the stator assembly and transferring thermal energy from the stator assembly to the temperature sensor. This increases compactness and simplicity of the sensor mounting bracket. Optionally, the fixing feature comprises an aperture or opening configured to receive at least part of a fastener for fixedly mounting the sensor mounting bracket to the stator assembly. Optionally, the fixing feature comprises a substantially semi-circular opening. The opening may be in a side edge of the heat-transfer portion. The opening may be defined at a distal end of the heat-transfer portion. Where the heat-transfer portion comprises a planar contact surface, the opening may be in the distal edge of the planar contact surface. Advantageously, providing an aperture or opening configured to receive at least part of a fastener improves ease of assembly by allowing for some misalignment between the aperture or opening and the fastener during assembly. Optionally, the temperature sensor arrangement comprises a clip arrangement connected to the sensor mount and having at least one resiliently deformable clip for attaching the sensor mounting bracket to the stator assembly. Optionally, the clip arrangement is connected to the sensor mount separately to the fixing feature. Advantageously, providing the clip arrangement helps to clip the sensor mounting bracket to the stator assembly in the correct alignment during assembly, for example before the heat-transfer portion has been mounted to the stator assembly. Further, the clip arrangement is quick and simple to assemble and disassemble to the stator assembly. Additionally, in use, the clip arrangement helps to reduce vibration of the sensor mounting bracket relative to the stator assembly. Optionally, the at least one resiliently deformable clip comprises one or more deviation in profile. Optionally, the at least one resiliently deformable clip is substantially S-shaped. Advantageously, providing clips with one or more deviation in profile, for example S-shaped clips, helps to improve grip of the clip, thereby improving retention of the sensor mounting bracket to the stator assembly. Optionally, the at least one resiliently deformable clip comprises a pair of opposed resiliently deformable clips. Advantageously, the pair of opposed resiliently deformable clips exert a force on the stator assembly in opposing directions, thereby helping to clip the sensor mounting bracket to the stator assembly in a direction extending between the pair of resiliently deformable clips. Optionally, the at least one resiliently deformable clip is formed from a bronze alloy. Advantageously, the bronze clips are elastically deformable, thereby providing a securing grip and helping to prevent permanent deformation of the at least one resiliently deformable clip. Optionally, the sensor mount comprises a sensor mount plate which is continuous with the heat-transfer portion. Optionally, the temperature sensor is configured to measure the temperature of the sensor mount plate. Advantageously, providing a continuous sensor mount plate helps to simplify manufacture of the temperature sensor arrangement, whilst improving heat transfer from the heat-transfer portion to the sensor mount plate. A mount plate has a large surface are to volume ratio, thereby improving heat transfer from the heat-transfer portion to the sensor mount plate. Optionally, the heat-transfer portion and the sensor mount are unitary. The term “unitary” is used to mean that the heat-transfer portion and the sensor mount are formed from the same piece of material. For example, the heat-transfer portion and the sensor mount may be formed from a single piece of sheet metal. Optionally, the entire sensor mounting bracket is a unitary component. Advantageously, forming the heat-transfer portion and the sensor mount from a unitarily, for example from sheet metal, helps to simplify assembly and may improve heat transfer between the sensor mount and the heat-transfer portion. Forming the heat-transfer portion and the sensor mount from sheet metal increases the surface area to volume ratio of the sensor mounting bracket, thereby increasing thermal transfer therethrough. Optionally, the heat-transfer portion and the sensor mount are formed from a sheet metal with a constant cross-section. Optionally, the sensor mounting bracket has a substantially L-shaped cross-sectional shape. Advantageously, the L-shaped cross-section can enable the bracket to be secured closer to the stator assembly and can reduce the overall height of the sensor mounting bracket, thereby improving compactness of the sensor mounting bracket. Optionally, the sensor mounting bracket is formed from a material having a thermal conductivity coefficient of at least 50 W / mK, optionally at least 200 W / mK. Optionally, the sensor mounting bracket is formed from a material having a thermal conductivity coefficient of at least 100 W / mK, at least 120 W / mK, at least 150 W / mK, or at least 180 W / mK. The sensor mounting bracket may be formed from a metal, such as steel or aluminium. According to another aspect of the present teachings, there is provided an electric traction motor for a vehicle, the electric traction motor comprising: a housing defining a stator cavity; a stator assembly at least partially located in the stator cavity, the stator assembly comprising: a plurality of stator windings; and a terminal connector for connecting at least one of the plurality of stator windings to an electrical power source, wherein the terminal connector is formed from a thermally conductive material and comprises a first terminal portion adjacent to the stator windings and a second terminal portion located outside of the stator cavity; and a temperature sensor arrangement of a previous aspect, wherein the sensor mounting bracket is fixed to the stator assembly such that the heat-transfer portion is in thermal contact with the second terminal portion. Advantageously, the thermal contact between the heat-transfer portion and the second terminal portion enables the at least one temperature sensor to accurately measure the temperature of the stator assembly via the temperature sensor mounting bracket, for example from a location remote from the stator assembly. This helps to improve ease of assembly and packaging of the electric traction motor, as integrating the temperature sensor arrangement closer to the electric traction motor (i.e. the heat source) is challenging. Optionally, the second terminal portion and the heat-transfer portion are in contact at a planar interface. Advantageously, a planar interface helps to increase the thermal contact area at the interface and is space efficient, thereby improving compactness of assembly of the temperature sensor arrangement to the stator assembly. Optionally, the second terminal portion comprises a planar terminal connector and the heat-transfer portion comprises a planar contact surface which is secured to the planar terminal connector to form the planar contact interface. Advantageously, a planar terminal connector and a planar contact surface each have a large surface area to volume ratio, thereby increasing heat transfer from the stator assembly to the sensor mount. A substantially planar contact interface helps to increase the thermal contact area and is space efficient, thereby improving compactness of assembly of the temperature sensor arrangement to the stator assembly. The planar contact surface can also enable the sensor mounting bracket to be sandwiched between the planar terminal connector and an additional flat surface of the stator assembly to improve heat transfer and / or ensure secure fixation of the sensor mount. Optionally, the second terminal portion is a busbar connector plate. Optionally, the sensor mounting bracket is fixed to the stator assembly such that the heat-transfer portion is in thermal contact with the busbar connector plate. Advantageously, a busbar connector plate has a large surface area to volume ratio, thereby increasing heat transfer from the stator assembly to the sensor mount. A busbar connector plate is also space efficient, thereby improving compactness of assembly of the temperature sensor arrangement to the stator assembly. Optionally, the stator assembly comprises a power supply connector plate secured to the busbar connector plate with a threaded fastener to connect the busbar connector plate to a power supply. Optionally, the heattransfer portion is fixed to the busbar connector plate by the threaded fastener. Optionally, the busbar connector plate is sandwiched between the heat-transfer portion and the power supply connector plate. Advantageously, fixing the heat-transfer portion to the busbar connector plate and the power supply connector plate provides a compact arrangement and helps to minimise the number of fixing features, for example fasteners, used to assemble the stator assembly. This helps to improve ease of assembly. According to another aspect of the present teachings, there is provided a vehicle comprising an electric traction motor according to a previous aspect. According to another aspect of the present teachings, there is provided a sensor mounting bracket for holding a temperature sensor in place in relation to a stator assembly of an electric traction motor, the sensor mounting bracket comprising: a sensor mount configured to be coupled to at least one temperature sensor; an attachment portion connected to the sensor mount and having an attachment plate configured to fixedly mount the sensor mounting bracket to the stator assembly; and a clip arrangement connected to the sensor mount and having at least one resiliently deformable clip configured to clip the sensor mounting bracket to the stator assembly prior to mounting of the attachment plate. Advantageously, providing the clip arrangement helps to clip the sensor mounting bracket to the stator assembly in the correct alignment during assembly, for example before the attachment portion has been mounted to the stator assembly. Further, the clip arrangement is quick and simple to assemble and disassemble to the stator assembly. Additionally, in use, the clip arrangement helps to reduce vibration of the sensor mounting bracket relative to the stator assembly. According to another aspect of the present teachings, there is provided a method of mounting a temperature sensor to a stator assembly, the method comprising: providing a stator assembly comprising a plurality of stator windings; providing a sensor mounting bracket comprising a sensor mount, an attachment portion connected to the sensor mount and having a fixing feature, and a clip arrangement connected to the sensor mount and having at least one resiliently deformable clip; coupling a temperature sensor to the sensor mount; clipping the sensor mount to the stator assembly via the at least one resiliently deformable clip; fixing the fixing feature of the attachment portion to the stator assembly, wherein the step of clipping the sensor mount to the stator assembly occurs prior to the step of fixing the fixing feature of the attachment portion to the stator assembly. Advantageously, clipping the sensor mount to the stator assembly prior to fixing the fixing feature of the attachment portion helps to clip the stator assembly in the correct alignment during assembly before the attachment portion has been mounted to the stator assembly. This helps to enable the sensor mounting bracket to be held in the correct position without the fixing feature being fixed to the stator assembly. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a vehicle in accordance with an embodiment of the invention; Figure 2 shows a schematic illustration of a sub-system of the vehicle of Figure 1; Figure 3 shows a view of part of an electrical drive unit (EDU) with a busbar mounting connector; Figure 4 shows an enlarged view of part of the EDU of Figure 3 with an end cover removed; Figure 5 shows an enlarged view of a busbar mounting connector of the EDU of Figures 3 and 4; Figure 6 shows a busbar assembly in accordance with an embodiment of the invention; Figure 7 shows a busbar mounting connector in accordance with an embodiment of the invention; Figure 8 shows an underside view of the busbar mounting connector of Figure 7; Figure 9 shows a top view of a busbar assembly in accordance with an embodiment of the invention; Figure 10 shows a transverse cross-sectional view of the busbar assembly of Figure 9 through a first plane; Figure 11 shows a transverse cross-sectional view of the busbar assembly of Figure 9 through a second plane below the first plane, with a temperature sensor arrangement in accordance with an embodiment of the invention; Figure 12 shows a front isometric view of a temperature sensor arrangement in accordance with an embodiment of the invention; Figure 13 shows a rear isometric view of the temperature sensor arrangement of Figure 12; Figure 14 shows an enlarged cross-sectional view of the busbar assembly of Figure 9, showing the clipping attachment of the temperature sensor arrangement to the busbar mounting connector; Figure 15 shows an enlarged isometric view of the busbar assembly of Figure 9, with a central busbar removed for clarity; and Figure 16 shows a cross-sectional side view of the busbar assembly of Figure 9 taken through a central busbar seat; and Figure 17 shows a flow chart of a method of mounting a temperature sensor to a stator assembly of a vehicle in accordance with an embodiment of the invention. DETAILED DESCRIPTION As shown in Figure 1, a vehicle 1 is a wheeled passenger vehicle having a subsystem 4 and an optional charging port 22. The passenger vehicle 1 depicted is of the 4x4 or SUV type, however the vehicle 1 may be 7 a car, a van, a light goods vehicle, or other such vehicle. The sub-system 4 of the vehicle 1, including an electrical storage means 20 and a portion of the powertrain 2, is shown schematically in Figure 2. The vehicle 1 has a powertrain 2. The powertrain 2 comprises a propulsion system comprising at least one prime mover 10. The prime mover(s) 10 are selectively operable for the purpose of providing drive torque for accelerating the vehicle 1. In alternative configurations with two prime movers 10, the first prime mover 10 may provide drive to a front axle and the second prime mover 10 may provide drive to a rear axle, or vice versa. In such an embodiment both prime movers 10 may be supplied electrical energy from electrical storage means 20. The prime mover 10 is an electric traction motor 10. Where a plurality of prime movers are provided, they may be a plurality of electric traction motors 10. The vehicle 1 may be a fully electric vehicle having only an electric machine as a power source for propulsion and no internal combustion engine or may be a hybrid vehicle having both an electric machine and an internal combustion (IC) engine arranged to propel the vehicle 1. The electric machine is powered by a battery which may be a traction battery or battery module. The vehicle 1 may be a plug-in hybrid electric vehicle (PHEV) or a mild hybrid electric vehicle (MHEV). In alternative embodiments, the vehicle 1 may be a hydrogen electric vehicle (HEV) and hence the electric machine may be powered by a hydrogen fuel cell arrangement comprising one or more hydrogen fuel cells. Thus the following description directed to a battery powered electric vehicle may also apply to a hydrogen electric vehicle. The at least one prime mover 10 comprises an electric traction motor 10. Thie electric motor is arranged to convert electrical energy into kinetic energy in the form of mechanical torque and may also be arranged to convert kinetic energy into electrical energy. The electric traction motor 10 may be an alternating current induction motor or a permanent magnet motor, or another type of suitable electric machine. The electric traction motor 10 is a traction motor configured to enable at least an electric mode comprising electric-only driving. That is, the electric traction motor 10 can drive the vehicle 1 by itself (without additional torque provided by a second torque source such as an IC engine). The electric traction motor 10 may form part of an electric drive unit 10 (EDU). The terms “electric traction motor” and “electric drive unit” may be used interchangeably throughout the present application. In order to store electrical energy for the electric traction motor 10, the vehicle 1 comprises electrical energy storage means 20. The electrical energy storage 20 means may be a traction battery 20. The traction battery 20 provides a nominal voltage required by electrical power users such as the electric traction motor 10. The traction battery 20 may be a high voltage battery. The traction battery 20 may have a voltage and capacity to support electric only driving for sustained distances. The traction battery 20 may have a capacity of several kilowatt-hours, to maximise range. The capacity may be in the tens of kilowatt-hours, or even over a hundred kilowatt-hours. The traction battery 20 may be charged using a charging port 22 located on the vehicle as shown schematically in Figure 1. The traction battery 20 may also be charged by the conversion of kinetic energy into electrical energy by the electric traction motor 10. In alternative configurations there may be additional electrical storage means 20 located in different points of the vehicle 1 each of the electrical storage means 20 providing electrical energy to the prime mover 10. An inverter 30 may be provided to convert between the direct current (DC) output of the traction battery 20 and the alternating current (AC) input required for the electric machine 10. For example, the DC output may be converted to a three-phase electrical power AC input, or a two-phase electrical power AC input. The EDU 10 may therefore be a three-phase traction motor 10 or a two-phase traction motor 10 as appropriate. The prime mover(s) 10 are selectively operable for the purpose of providing drive torque for accelerating the vehicle 1. In alternative configurations with two prime movers 10, the first prime mover 10 may provide drive to a front axle and the second prime mover 10 provides drive to a rear axle, or vice versa. In such an embodiment both prime movers may be supplied electrical energy from the electrical storage means 20. An EDU 10 in accordance with an embodiment of the invention is shown in Figure 3, 4 and 5. The EDU 10 has a stator assembly 12, a stator cavity 14, an EDU housing 16 and a busbar assembly 100. For reasons of clarity, a portion of the EDU housing 16 has been removed in Figures 3 to 5 in order to more clearly show the stator assembly 12 and arrangement of components located within the EDU housing 16, for example, the busbar assembly 100. The busbar assembly 100 is at least partially located in the stator cavity 14 of the EDU 10 as shown in Figure 3. The busbar mounting assembly 100 may extend out of the stator cavity 14 in some embodiments. The busbar assembly 100 shown in Figure 3 has a busbar mounting connector 40. The busbar mounting connector 40 is used to mount a first busbar 60, a central busbar 70 and a second busbar 80 to the stator assembly 12. Such a configuration enables three-phase AC electric power to be supplied from the inverter 30 to the stator assembly 12 of the three-phase EDU 10. Alternatively, where only two-phase AC electric power is used, only a first and second busbar 60, 80, may be utilised to supply power to a two-phase EDU 10. Additionally, the busbars 60, 70, 80 are configured to enable electrical power transfer from the stator assembly 12 to the traction battery 20 for storage when the EDU 10 is converting kinetic energy into electrical energy. Each of the busbars 60, 70, 80 are fixed to a terminal 72 of the inverter 30 by a fastener 102 as is shown in Figure 16. The fasteners 102 are bolts with an optional spacer 103 which fasten a single busbar 60, 70, 80 to each inverter terminal 30. Each of the bolts 102 is connect to a nut 48 disposed in the busbar mounting connector 40. As shown in Figure 4, the busbar assembly 100 has a temperature sensor arrangement 200. The temperature sensor arrangement 200 is located on a portion of the busbar mounting connector 40 such that it is radially closer to a stator axis A of the stator assembly 12 than the busbars 60, 70, 80 as shown in Figure 4. The temperature sensor arrangement 200 is configured to measure the stator temperature in use, as will be described in more detail below. The temperature sensor arrangement 200 may have a first temperature sensor 210 and optionally a second temperature sensor 212 (see Figure 12). The busbar assembly 100 and busbar mounting connector 40 will be described in more detail with the aid of Figures 5 to 11. The busbar assembly 100 is shown in Figure 6 alone and without the EDU 10 or other components. As can be seen each of the busbars 60, 70 and 80 comprise a first terminal portion 61b, 71b, 81b and a second terminal portion 61a, 71a, 81a remote from the first terminal portion 61b, 71b, 81b. The second terminal portion 61a, 71a, 81a is a busbar connector plate, also referred to as an inverter connector 61a, 71a, 81a, and the first terminal portion is a stator connector 61b, 71b, 81b. The stator connectors 61 b, 71b, 81b are welded to stator windings 15 of the stator assembly of the EDU 10. The stator connectors 61b, 71b, 81b are two prongs which extend from the busbars 60, 70, 80 however in alternative configurations the stator connectors 61b, 71b, 81b may be a single prong ora portion of the body of the busbar 60, 70, 80 itself or any alternative portion suitable for connection to a stator assembly 12. The busbar mounting connector 40 enables the busbars 60, 70, 80 to be held in use and maintain an electrical clearance between the busbars 60, 70, 80 at the inverter connectors 61a, 71a, 81a. This reduces the likelihood of short circuits between the busbars 60, 70, 80 use. The busbar mounting connector 40 has a first seat 42 configured to receive the first busbar 60, a central seat 44 to receive the central busbar 70, and a second seat 46 to receive the second busbar 80. The seats 42, 44, 46 are configured to receive at least a portion of the respective busbars 60, 70, 80. The first seat 42 has a portion for supporting a bottom surface of the first busbar 60. As shown in Figure 8, the busbar 60 abuts the bottom surface of the first seat 42. The second seat 46 has a similar portion for supporting a bottom surface of the second busbar 80. As shown in Figure 8, the second busbar 80 abuts the bottom surface of the second seat 46. The busbar mounting connector 40 has a first wall 50 between the first seat 42 and central seat 44. The first wall 50 enables a lateral spacing between the first and central busbars 60, 70 in use. As evident from Figures 8 and 9, the first busbar 60 abuts the first seat 42 surface and the first wall 50. The busbar mounting connector 40 has a second wall 52 between the central seat 44 and the second seat 46. The second wall 52 enables a lateral spacing between the central and second busbars 70, 80 in use. As can be seen in Figures 8 and 9, the second busbar 80 abuts the second seat 46 surface and the second wall 52. The central seat 44 comprises an inner facing surface of both the first and second walls 50, 52. In use, the central busbar 70 is retained between the first and second walls 50, 52 by means of a fixed fit or interference fit. A portion of the inner facing surface of one or both of the first and second walls 50, 52 may be complementary to the shape of the central busbar 70 to facilitate the fixed fit or interference fit. The central busbar 70 may be retained on the busbar mounting connector 40 by means of the fixed fit or interference fit alone in use. One or both of the first and second walls 50, 52 may have a tapered end 51. The tapered end 51 helps to maintain electrical creepage clearance between the different phases of the busbars 60, 70 and 80. Further, the tapered end 51 helps with assembly of the busbar assembly 100 as the tapered end 51 can assist with guiding a busbar 60, 70, 80 into a busbar seat 42, 44, 46 when a busbar 60, 70, 80 is inserted into the busbar mounting connector 40 in a direction substantially parallel to the first and / or second walls 50, 52. The busbar mounting connector 40 has a first retaining arm 54 that is used to retain the first busbar 60 in the first seat 42 in use as shown in Figures 6 to 10. The first retaining arm 54 is biased such that when the busbar 60 is inserted into the seat 42 the first retaining arm 54 is resiliently deflected away from, and tries to return to, its unbiased position. The first retaining arm 54 provides a retaining force on the first busbar 60 towards wall 50 and / or seat 42. As can be seen in Figure 10, the first retaining arm 54 has a busbar retaining feature 55. The busbar retaining feature 55 is complementary to a cutout 62 on the first busbar 60, The busbar retaining feature 55 engages the cutout 62 to reduce movement of the first busbar 60 when it is located in the first seat 42. As can be seen in Figure 10, which shows a partial cutaway view of the busbar assembly 100, the busbar retaining feature 55 has a barb 58 or shoulder which is configured to engage with a busbar ledge of the cutout 62. The barb 58 engaging with the busbar ledge of the cutout 62 helps to prevent the removal of the first busbar 60 whilst the retaining feature 55 is engaged with the complementary cutout 62. The retaining feature 55 has a sloped profile 59 shown in Figure 10. The sloped profile 59 is located on an upper surface of the busbar retaining feature 55 such that when the first busbar 60 is being inserted into the first seat 42, the first busbar 60 engages the sloped profile 59 causing the first retaining arm 54 to move laterally away from the first busbar 60 and the wall 50 as the busbar is inserted. This occurs until the barb 58 is able to enter the cutout 62, at which point the first retaining arm 54 moves back laterally towards the first wall 50. The busbar mounting connector 40 has a second retaining arm 56 that is used to retain the second busbar 80 in the second seat 46 in use as shown in Figures 6 to 10. The second retaining arm 56 is biased such that when the second busbar 80 is inserted into the second seat 46 the second retaining arm 56 is deflected away from the second wall 52 and tries to return to its unbiased position. The second retaining arm 56 provides a retaining force on the second busbar 80 towards the second wall 52 and / or seat 46. As can be seen in Figure 10, the second retaining arm 56 has a busbar retaining feature 57. The busbar retaining feature 57 is complementary to a cutout 82 on the second busbar 80. The busbar retaining feature 57 engages the cutout 82 to reduce movement of the second busbar 80 when it is located in the second seat 46. As can be seen in Figure 9, which shows a partial cutaway view of the busbar assembly 100, the busbar retaining feature 57 has a barb 58 or shoulder which is configured to engage with a busbar ledge of the cutout 82. The barb 58 engaging with ledge of cutout 82 helps to prevent the removal of the second busbar 80 whilst the retaining feature 57 is engaged with the complementary cutout 82. The retaining feature 57 has a sloped profile 59 shown in Figure 10. The sloped profile 59 is located on an upper surface of the busbar retaining feature 57 such that when the second busbar 80 is being inserted into the second seat 46, the second busbar 80 engages the sloped profile 59 causing the second retaining arm 56 to move laterally away from the second busbar 80 and the second wall 52. This occurs until the barb 58 is able to enter the cutout 82 at which point the second retaining arm 56 moves back laterally towards the second wall 52. As shown in Figures 3-11 each of the busbars 60, 70, 80 have a respective aperture 64, 74, 84. Taking the first busbar 60 for example, the aperture 64 is a through aperture which is sized to receive a fastener 102. The fastener 102 is used to fix the first busbar 60 to the inverter terminal 30. The busbar mounting connector 40 has a recess 43 in each of the first, second and third seats 42, 44, 46 that is sized to receive and retain a nut 48. The recesses 43 are shown without the nut in Figure 7. The nut 48 is shown in Figure 11 received in the recess 43 of the busbar mounting connector 40 for seats 42, 44, 46. The recesses 43 have ridges which provide increased stiffness to reduce the likelihood of the nut 48 rotating in the recess 43 in use, as well as to retain the nut in position during assembly. The bolts 102 are shown connecting the busbar 70 to an electrical terminal connector plate 72 of inverter 30 in Figure 16. In the embodiments described in the Figures, the busbar mounting connector 40 is unitary in construction. That is, formed of the same material throughout, such as the same polymer. In alternative configurations, the busbar mounting connector 40 may be made up of two different materials which may be co-moulded. For example, a first part of the busbar mounting connector 40 may be made of a first polymer and a second part of the busbar mounting connector 40 may be made of a second polymer. The busbar mounting connector 40 is manufactured by an injection moulding process from a polymer. The polymer may be a thermoset or thermoplastic material. The polymer may be any one of: a polyamide, polyamide-imide, polyether ether ketone (PEEK), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), an aliphatic polyamide (PPA), a polyoxymethylene (POM), a polypropylene (PP), a polymethyl methacrylate (PMMA) or other suitable polymer material. The polymer may be a polymer blend of any combination of the polymers previously described. The injection moulding process may be a one-shot injection moulding process or a co-moulding process. Alternatively, the busbar mounting connector 40 may be manufactured by a 3D printing process from a material suitable for 3D printing (e.g. a 3D printable polymer or polymer blend) using means and methods known in the art. Whilst not shown in the Figures each of the seats 42, 44, 46 may have indicators moulded or machined into them. These indicators indicate which busbar 60, 70, 80 is located in which seat 42, 44, 46. For example, the first seat 42 may have a W, the second seat 44 having a ‘V’ and the third seat 46 having a 'U’. The letters W, V and U corresponding to the phase of the busbar 60, 70, 80 that is located in that seat 42, 44, 46. Such indicators aid assembly of the stator assembly 12 and maintenance of the vehicle 1 and EDU 10 in use. Thus the busbar mounting connector 40 serves several purposes. Prior to assembly of the traction machine in a vehicle, it connects the two or three (as the case may be) busbars together, keeping them separate and isolated from one another. (This role continues after installation of the motor in a vehicle.) It mounts and retains the nuts 48 in position, even when the fastener 102 is absent prior to assembly in a vehicle and connection of the inverter 30 terminals 72. Further it locks the nuts in a rotationally fixed position so that it is only necessary to turn the fastener 102 when attaching the terminals 72. And further it mounts, and locates for connection on assembly, the optional temperature sensor described further below. The traction motor is therefore ready for assembly in a vehicle. As shown in Figure 3, the stator assembly 12 has a temperature sensor arrangement 200. The temperature sensor arrangement 200 is for measuring a temperature of the stator assembly 12 located in the stator cavity 12 of the electric traction motor 10. The temperature sensor arrangement 200 is disposed on the busbar mounting connector 40. The temperature sensor arrangement 200 is shown in more detail in Figures 12 and 13. The temperature sensor arrangement 200 has a sensor mounting bracket 204 for mounting one or more temperature sensors 210, 212 to the stator assembly 12. In the embodiment shown in Figures 12 and 13, a first temperature sensor 210 and a second temperature sensor 212 are provided, however in alternative embodiments any suitable number of temperature sensors 210, 212 may be provided, for example one temperature sensor or three or more temperature sensors. The sensor mounting bracket 204 may include one or more of a fixing feature 220, a sensor mount 206 and a heat-transfer portion 208 (also referred to as an attachment portion 208). The sensor mount 206 is configured to couple the sensor(s) 210, 212 to the sensor mounting bracket 204. The sensor mount 206 and first and second temperature sensors 210, 212 are located on a front face of the temperature sensor arrangement 200. The front face of the temperature sensor arrangement 200 faces away from the busbar mounting connector 40, as illustrated in Figures 15 and 16. The temperature sensor arrangement 200 includes a rear face opposing the front face and facing towards the busbar mounting connector 40. As shown in Figure 4, the temperature sensor arrangement 200 is located radially closer to a stator axis A than the busbars 60, 70, 80. In use, the front face of the sensor arrangement 200 is located radially inward in the stator assembly 12 facing the stator axis A shown in Figure 2 and 3, and the rear face is located radially outward and facing away from the stator axis A. The heat-transfer portion 208 extends from the sensor mount 206. The heat-transfer portion 208 is in thermal contact with the sensor mount 206 so that the heat-transfer portion 208 is able to transfer heat from the stator assembly 12 to the sensor mount 206 when the temperature sensor arrangement 200 is connected to the stator assembly 12. The temperature sensors 210, 212 are configured to measure a temperature of the sensor mount 206. In particular, as the sensor mount 206 is in thermal contact with both the temperature sensors 210, 212 and the heat-transfer portion 208, the heat-transfer portion 208 is arranged to transfer heat of the stator assembly 12 to the temperature sensors 210, 212, so as to enable the temperature sensor 210, 212 to indirectly measure the temperature of the stator assembly 12. The thermal contact between the heat-transfer portion 208 and the sensor mount 206 enables the at least one temperature sensor to accurately measure the temperature of the stator assembly 12 via the sensor mounting bracket 204, for example from a location remote from the stator assembly 12. In particular, the temperature of the stator assembly 12 can be measured from a location outside of the stator cavity 14 of the electric traction motor 10. This helps to improve ease of assembly and packaging of the electric traction motor 10, as integrating the temperature sensor arrangement 200 closer to the electric traction motor 10 is challenging. The sensor mounting bracket 204 is formed from a thermally conductive material. That is, the sensor mounting bracket 204 may be formed from a material having a thermal conductivity of at least 50 W / mK, at least 100 W / mK, at least 120 W / mK, at least 150 W / mK, or at least 180 W / mK. In the embodiment of the Figures, the sensor mounting bracket 204 is formed from a material having a thermal conductivity of at least 200 W / mK. The sensor mounting bracket 204 may be formed from a metal, such as an iron alloy, steel, copper alloy or aluminium alloy. The heat-transfer portion 208 of the sensor mounting bracket 204, the busbar connector plate 71a and the power supply connector plate 72 are shown assembled together in Figures 15 and 16. The power supply connector plate 72 from the inverter 30 is secured to the busbar connector plate 71a by the fastener 102. The busbar connector plate 71a is sandwiched between the heat-transfer portion 208 and the power supply connector plate 72. This arrangement helps to improve uniformity of resistance between the different phases of the busbar, 60, 70, 80. Additionally, this arrangement helps to prevent electrical interference from the power supply connector plate 72, thereby improving accuracy of the temperature measurement by the temperature sensors 210, 212. The heat-transfer portion 208 has a fixing feature 220 for fixedly mounting the sensor mounting bracket 204 to the stator assembly 12. Providing the fixing feature 220 on the heat-transfer portion 208 enables the heattransfer portion 208 to perform the dual function of fixing the sensor mounting bracket 204 to the stator assembly 12 and transferring thermal energy from the stator assembly 12 to the temperature sensors 210, 212. This helps to increase compactness and simplicity of the temperature sensor arrangement 200. In alternative embodiments, where the portion 208 does not perform the function of transferring heat to the temperature sensors 210, 212, the portion 208 may instead be referred to as an attachment portion 208. The fixing feature 220 is complementary to fit around the fastener 102 used to retain the central busbar 70 in the central seat 44, in use. The same fastener 102 is also used to secure the power supply connector plate 72 to the heat-transfer portion 208 and the busbar connector plate 71a. The fixing feature 220 is an aperture or opening 220 configured to receive at least part of the fastener 102. In particular, the fixing feature 220 is an open aperture or scallop, for example a semi-circular opening 220. Providing an aperture or opening 220 configured to receive at least a part of the fastener 102 improves ease of assembly by allowing for some misalignment between the aperture or opening 220 and the fastener 102 during assembly. Alternatively, the fixing feature 220 may be a closed aperture which in use is co-axial with the aperture 74 of the central busbar 70. The opening 220 may be in a side edge of the heat-transfer portion 208. In the embodiment shown in Figures 12 and 13, the opening 220 is defined at a distal end of the heat-transfer portion 208. The distal end of the heat-transfer portion 208 is the end remote from the sensor mount 206. Put another way, the heattransfer portion 208 includes a fixed end which is connected to the sensor mount 206, and a free end which is remote from the fixed end, and the opening 220 is located on the free end. As shown in Figures 12, 13, 15 and 16, the heat-transfer portion 208 includes a planar contact surface 208a. The planar contact surface 208a is arranged to contact the busbar terminal 71a at a planar interface. In particular, the planar contact surface 208a is arranged to contact the central busbar 70, in use, as is shown in Figure 16 such that the heat-transfer portion 208 is in thermal contact with the busbar connector plate 71a at the planar interface. The heat-transfer portion 208 therefore enables heat transfer from the central busbar 70 to the first and / or second temperature sensors 210, 212. There is one heat-transfer portion 208 provided in the embodiment shown in the Figures. In alternative embodiments, there may be any suitable number of heat-transfer portions 208 provided, as will be described in more detail below.The planar contact surface 208a has a large surface area to volume ratio, thereby increasing heat transfer from the stator assembly 12 to the sensor mount 206. A planar contact interface between the planar contact surface 208a and the second terminal portion 71a helps to increase the thermal contact area and is space efficient, thereby improving compactness of assembly of the temperature sensor arrangement 200 to the stator assembly 12. The planar contact surface 208a can also enable the sensor mounting bracket 204 to be sandwiched between two flat surfaces of the stator assembly 12 (for example planar faces of the busbar connector mount 40 and the busbar connector plate 71a) to improve heat transfer and / or ensure secure fixation of the sensor mount 206. In further alternative embodiments, the heat-transfer portion 208 may be in thermal contact with any thermally conductive portion of the stator assembly 12 so as to indirectly measure the temperature thereof, for example a thermally conductive connection ring or a stator core of the stator assembly 12. In the embodiment shown in the Figures, the sensor mount 206 is unitary with the heat-transfer portion 208. The term “unitary” means here that the heat-transfer portion 208 and the sensor mount 206 are formed from the same piece of material, for example a single piece of sheet metal. The heat-transfer portion 208 and the sensor mount 206 may be formed from sheet metal with a constant cross-section. In some embodiments, the entirety of the sensor mounting bracket 204 may be a unitary component. In alternative embodiments, the sensor mounting bracket 204 may be formed from separate pieces which are thermally connected (i.e. in thermal contact). For example, the sensor mount 206 and the heat-transfer portion 208 may be formed separately and connected together. The sensor mount 206 includes a sensor mount plate 206a. The sensor mount plate 206a is continuous with the heat-transfer portion 208 and extends therefrom. In embodiments where the heat-transfer portion 208 is unitary with the sensor mount 206, the sensor mount plate 206a forms a part of a wall of the sensor mount 206. Forming the heat-transfer portion 208 and the sensor mount 206 from a unitary sheet, for example sheet metal, helps to simplify assembly and may improve heat transfer between the sensor mount 206 and the heat-transfer portion 208. Forming the heat-transfer portion 208 and the sensor mount 206 from sheet metal increases the surface area to volume ratio of the sensor mounting bracket 204, thereby increasing thermal transfer therethrough. The heat-transfer portion 208 extends from the sensor mount 206 at a non-zero angle. In the embodiment shown in Figure 15, the heat-transfer portion 208 extends substantially perpendicularly from the sensor mount 206. As such, the sensor mounting bracket 204 has a substantially L-shaped cross-sectional shape. The L-shaped cross-sectional shape is formed by the sensor mount 206 and the heat-transfer portion 208. It shall be appreciated that alternative cross-sectional shapes may be used. For example, the sensor mounting 15 bracket 204 may be substantially l-shaped or linear when mounted straight (i.e. as opposed to being bent into the L-shaped cross-sectional shape shown in Figure 16). In further alternative embodiments, the sensor mounting bracket 204 may have a substantially T-shaped, F-shaped or E-shaped cross-sectional shape, for example if more than one heat-transfer portion 208 is provided extending from the sensor mount 206. The temperature sensor arrangement 200 includes a clip arrangement 202 connected to the sensor mount 206. The clip arrangement 202 includes at least one resiliently deformable clip 202 for attaching the sensor mounting bracket 204 to the busbar mounting assembly 40 and keeping it in place prior to connection of the inverter terminals 72 to the busbar 70, as shown in Figure 15, for example. The at least one deformable clip 202 may be formed from any suitable material, for example a bronze alloy. Such bronze deformable clips are elastically deformable, thereby providing a secure grip and helping to prevent permanent deformation of the at least one resiliently deformable clip 202, in use. The clips 202, as shown in Figure 11, engage a portion of the busbar mounting assembly 40 adjacent to the central seat 44. The clips 202 retain the temperature sensor arrangement 200 on the busbar mounting assembly 40 in use and during assembly. Providing the clip arrangement 202 helps to clip the sensor mounting bracket 204 to the stator assembly 12 in the correct alignment during assembly, for example before the heat-transfer portion 208 has been mounted to the stator assembly 12 via the fixing feature 220. Further, the clip arrangement 202 is quick and simple to assemble and disassemble to the stator assembly 12. Additionally, in use, the clip arrangement 202 can help to reduce vibration or rotation of the sensor mounting bracket 204 relative to the stator assembly 12. The at least one resiliently deformable clip 202 comprises a pair of opposed resiliently deformable clips 202. The pair of opposed resiliently deformable clips 202 exert a force on the stator assembly 12, for example on the bus bar mounting connector 40, in opposing directions, thereby helping to clip the sensor mounting bracket 204 to the stator assembly 12 in a direction extending between the pair of resiliently deformable clips 202. The pair of opposed resiliently deformable clips 202 extend from opposing sides of the sensor mount 206, as illustrated in Figure 13. In particular, the pair of resiliently deformable clips 202 extend in a direction away from the temperature sensors 210, 212. It shall be appreciated that in alternative embodiments, any suitable number of resiliently deformable clips 202 may be provided, for example two pairs of opposed resiliently deformable clips 202. As illustrated in Figure 14, the resiliently deformable clips 202 each include one or more deviation in profile. The one or more deviations in profile are visible in plan view. The resiliently deformable clips 202 are substantially S-shaped. As such, the resiliently deformable clips 202 include two deviations in profile in plan view. The resiliently deformable clips 202 act in pairs such that the resiliently deformable clips 202 are symmetrical about the sensor mount 206. The one or more deviation in profile may be curved or linear. Furthermore, it shall be appreciated that any suitable number of linear or curved deviations in profile, or a combination thereof, may be provided. Figure 17 illustrates the steps of method 300 according to an embodiment of the present teachings. The method of mounting a temperature sensor 210, 212 to a stator assembly 12, such as the stator assembly 12 of Figures 1 to 16 for an electric traction motor 10, is described below. The method includes the step S310 which comprises providing a stator assembly 12 including a plurality of stator windings 15 and providing a sensor mounting bracket 204 comprising a sensor mount 206 and an attachment portion 208 connected to the sensor mount 206. The attachment portion 208 has a fixing feature 220. The sensor mounting bracket 204 includes a clip arrangement 202 connected to the sensor mount 206 and having at least one resiliently deformable clip 202. At step S320, a temperature sensor 210, 212 is coupled to the sensor mount 206. In particular, the temperature sensor 210, 212 is mounted or coupled to a front face of the temperature mounting sensor arrangement 200. At step S330 the sensor mount 206 is clipped to the stator assembly 12 via the at least one resiliently deformable clip 202. In particular, where a pair of resiliently deformable clips 202 are provided, the pair of resiliently deformable clips 202 are moved away from one another and part of a busbar mounting connector 40 is located therebetween. The resiliently deformable clips 202 are released and engage the busbar mounting connector 40 to clip the sensor mounting bracket 204 to the busbar mounting connector 40 in a direction extending between the pair of resiliently deformable clips 202. Whilst the sensor mounting bracket 204 is coupled to the busbar connector 40 by the resiliently deformable clips 202, the busbars 60, 70, 80 (for example first, central and second busbars 60, 70, 80) and the power supply connector plate 72 may be assembled to the stator assembly 12. At step S340, the fixing feature 220 of the attachment portion 208 is fixed to the stator assembly 12. In the embodiment Figure 16, a fastener 102 is provided to fix the attachment potion 208 to a busbar connector plate 71a of the central busbar 70. The step of clipping the sensor mount 206 to the stator assembly 12 occurs prior to the step of fixing the fixing feature 220 of the attachment portion 208 to the stator assembly 12. As such, the sensor mounting bracket 204 can be held in position during assembly of the traction motor 10 before the fixing feature 220 is fixed in position. This may be particularly advantageous in embodiments where the sensor mounting bracket 204 is assembled to the stator assembly 12 prior to the busbars 60, 70, 80, power supply connector plate 72 and / or alternative components being assembled to the stator assembly 12. In alternative embodiments, the central seat 44 may be omitted so that the busbar mounting connector 40 has only a first and second seat 424, 46 to receive a first and second busbar 60, 80 but not a central busbar 70. Such a configuration may be utilised where a two-phase traction motor 10 or EDU 10 is used. Alternatively, the three-seat configuration may be utilised but with one of the seats 42, 44, 46 unfilled as only two out of three busbars 60, 70, 80 may be utilised. In a two-seat 42, 46 configuration there may be a single first wall 50 separating the first and second seats 42, 44. In such a case both the first and second retaining arms 54, 56 have a retaining force directed towards the wall 50. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A temperature sensor arrangement for measuring a temperature of a stator assembly located in a stator cavity of an electric traction motor, the temperature sensor arrangement comprising:a temperature sensor; anda sensor mounting bracket for mounting the temperature sensor to the stator assembly,wherein the sensor mounting bracket comprises:a sensor mount coupled to the temperature sensor; anda heat-transfer portion extending from the sensor mount and in thermal contact with the sensor mount, wherein the heat-transfer portion is configured to transfer heat from the stator assembly to the sensor mount,wherein the temperature sensor is configured to measure a temperature of the sensor mount.

2. The temperature sensor arrangement according to claim 1, wherein the heat-transfer portion comprises a planar contact surface arranged to contact the stator assembly at a planar interface.

3. The temperature sensor arrangement according to claim 1 or claim 2, wherein the heattransfer portion comprises a fixing feature for fixedly mounting the sensor mounting bracket to the stator assembly.

4. The temperature sensor arrangement according to claim 3, wherein the fixing feature comprises an aperture or opening configured to receive at least part of a fastener for fixedly mounting the sensor mounting bracket to the stator assembly.

5. The temperature sensor arrangement according to any preceding claim, comprising a clip arrangement connected to the sensor mount and having at least one resiliently deformable clip for attaching the sensor mounting bracket to the stator assembly.

6. The temperature sensor arrangement according to claim 5, wherein the at least one resiliently deformable clip comprises a pair of opposed resiliently deformable clips.

7. The temperature sensor arrangement according to any preceding claim, wherein the sensormount comprises a sensor mount plate which is continuous with the heat-transfer portion, and wherein the temperature sensor is configured to measure the temperature of the sensor mount plate.

8. The temperature sensor arrangement according to any preceding claim, wherein the sensor mounting bracket is formed from a material having a thermal conductivity coefficient of at least 50 W / mK, optionally at least 200 W / mK.

9. An electric traction motor for a vehicle, the electric traction motor comprising:a housing defining a stator cavity;a stator assembly at least partially located in the stator cavity, the stator assembly comprising:a plurality of stator windings; anda terminal connector for connecting at least one of the plurality of stator windings to an electrical power source terminal, wherein the terminal connector is formed from a thermally conductive material and comprises a connection to the stator windings and a connector terminal; anda temperature sensor arrangement of any preceding claim, wherein the sensor mounting bracket is fixed to the stator assembly such that the heat-transfer portion is in thermal contact with the connector terminal.

10. The electric traction motor according to claim 10, wherein the connector terminal and the heat-transfer portion are in contact at a planar interface.

11. The electric traction motor according to claim 10 or 11, when dependent on claim 5, wherein the stator assembly comprises a busbar connector plate and an electrically insulating busbar mounting connector, whereinsaid connector terminal comprises said busbar connector plate,said clip arrangement is clipped to said busbar mounting connector to locate said heattransfer portion against said busbar connector plate.

12. The electric traction motor according to claim 11, wherein the busbar connector plate, when located in the busbar mounting connector, is adjacent a fastening component for fastening of a power source terminal to said connector terminal about said heat-transfer portion.

13. A vehicle comprising an electric traction motor according to any of claims 9 to 12.

14. A vehicle as claimed in claim 12, further comprising said power source terminal and acomplementary fastening element which, together with said fastening component, clamps together said power source terminal, said busbar connector plate and said heat transfer portion of the sensor mount.21

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