Stator winding device

Abstract

A stator for a rotating electric machine is disclosed, the stator comprising a stator core (16) comprising stator slots and a plurality of stator coils. The stator coils comprise side windings (17) located in the stator slots, end windings (18) extending from the stator slots, and end leads (28) for connecting the stator coils. The end leads (28) extend circumferentially around the radially outer side of the end windings (18). Spacers (34) may be provided to space the end leads apart from each other and from the end windings. This may help improve cooling, help improve electrical separation, and may be more efficient in terms of space requirements and ease of manufacture compared to previous arrangements.

Description

Technical Field

[0001] The present disclosure relates to winding arrangements for stators in rotating electrical machines, and more particularly to winding arrangements that can help reduce temperature increases and improve cooling of the electrical machine. Background Art

[0002] Rotating electrical machines such as motors and generators generally include a rotor mounted on a shaft and arranged to rotate inside a stator. The rotor includes a rotor core that holds rotor windings or permanent magnets. The rotor windings or permanent magnets generate a rotating magnetic field that crosses the air gap between the rotor and the stator. The stator includes a stator core that holds the stator windings (in combination with the rotating magnetic field).

[0003] In a rotating electrical machine, the stator windings are typically housed in stator slots that extend axially through the stator core. Typically, the stator windings comprise a plurality of coils arranged circumferentially around the stator. The coils may be wound in situ in the slots, or preformed coils may be inserted into the slots. In either case, the windings must exit one slot and pass around the outside of the stator before entering another slot. The portion of the winding that passes through the slots is typically referred to as the side winding, while the portion of the winding that extends outside the stator is typically referred to as the end winding or overhang winding. Coil end leads are typically provided for connection purposes.

[0004] It is often necessary to bring some or all of the coil end leads out of the stator for connection to external components. The number of end leads taken out depends on the connection method, parallel paths, voltage requirements, etc. The end leads are usually routed circumferentially around the stator so that they are brought to a common connection point (such as a terminal box). The end leads from different coils are usually bundled together in a ring adjacent to the end winding in the axial direction.

[0005] The power rating of an electric motor is usually limited by the temperature rise of the stator and rotor when the motor is in use. In addition, electric motors generally operate more efficiently at lower temperatures. In addition, if the motor is operated at a higher temperature, the service life of the motor will be reduced. For this reason, many electric motors are arranged so that air flows through the motor in order to cool the motor.

[0006] In a rotating electrical machine, the stator typically serves as the armature and carries the main electrical power. As a result, the end leads of the stator may be required to carry large currents. This, combined with the fact that the end leads are typically bundled together, can lead to increased temperature rise in the end windings. This in turn can lead to an increase in the overall temperature of the electrical machine.

[0007] In a multi-phase electric machine, the stator winding comprises a separate winding for each phase. This may result in the end leads of different phases being adjacent to each other when routed around the stator. In operation, each phase is at a different electrical potential. It is therefore necessary to ensure sufficient electrical insulation between the end leads of different phases.

[0008] The individual wires in the stator windings are usually electrically insulated by means of an outer insulation layer, usually an insulating varnish. Additional insulation may also be provided on the end leads. However, defects may occur in the outer insulation layer, either due to the manufacturing process or due to stresses applied to the wires during construction or use of insertion tools. In addition, the electrical insulation may degrade over time due to thermal, mechanical and environmental stresses. In the case where the end leads are at different electrical potentials, this may lead to arcing between the windings. This will make the motor inefficient and may cause damage to the motor and ultimately cause the motor to fail. Although it is in principle possible to reduce the risk of arcing by increasing the amount of insulation, this will reduce the amount of copper in a conductor of a given size, which will reduce efficiency and may cause further temperature increases.

[0009] It is known to provide a connector ring for connecting the individual stator coils to each other and to the output terminals. However, such a connector ring requires additional connections to be made, which increases the complexity of the manufacturing process. In addition, such a connector ring generally increases the overall size of the motor. Summary of the invention

[0010] It is therefore desirable to provide a winding arrangement that can help reduce temperature rise in the coil end leads. It is also desirable to provide a winding arrangement in which greater electrical separation can be achieved between the end leads of different phases without affecting thermal performance. In addition, it is desirable to provide a winding arrangement that is efficient in terms of space requirements and ease of manufacture.

[0011] According to one aspect of the present invention, there is provided a stator for a rotating electric machine, the stator comprising:

[0012] a stator core, the stator core comprising stator slots; and

[0013] a plurality of stator coils, the stator coils comprising side windings located in the stator slots, end windings extending from the stator slots, and end leads for connecting the stator coils;

[0014] Therein, at least some of the end leads extend circumferentially around the radially outer side of the end winding.

[0015] The invention may provide the following advantages: By extending the end leads circumferentially around the radially outer side of the end windings, cooling of the end leads and / or the end windings may be improved. This in turn may contribute to improving the motor life and / or enhancing the power density of the motor. Furthermore, the electrical separation between the phases in a multiphase motor may be improved. In addition, the winding arrangement may be made more efficient in terms of space requirements and / or ease of manufacture.

[0016] Preferably, the end leads are located on the radially outer side of the end winding. This can help ensure that the end leads are located in an area of ​​relatively high airflow and therefore can allow more cooling air to contact the end leads. However, in some cases, some of the end leads may be located on the radially inner side of the end winding. Some of the end leads may also be axially outer side of the end winding.

[0017] Preferably, the side windings extend through the stator slots (e.g. in a generally axial direction). Preferably, the end windings extend from one stator slot and into another stator slot. The end windings may extend in a generally circumferential direction between the stator slots. The end leads are preferably end leads of the respective coils. The end leads may be provided with terminals for connection to other components. Preferably, the end leads are arranged to be connected to external components such as a terminal box.

[0018] In order to connect the stator winding to a component such as a terminal box, it is usually necessary to extend the end winding circumferentially around the stator. Therefore, the end lead may extend circumferentially at least partially around the outside of the end winding.

[0019] Each stator coil is preferably wound from a single continuous conductor. Thus, each end lead is preferably part of the same continuous conductor as the side windings and end windings. This can avoid the need to make additional connections or separate conductor loops, which can help improve space efficiency and / or ease of manufacturing.

[0020] In a preferred embodiment, each coil is formed by a single continuous wire wound into a series of turns. The wire can be, for example, a metal wire, such as copper wire. Thus, each stator coil can be wound with wire forming side windings, end windings and end leads. This can help improve space efficiency and / or ease of manufacturing. However, if desired, the coil can be made of two or more sections of wire.

[0021] Preferably, the end leads are arranged in a row along the outside of the end winding (e.g., in a generally axial direction). The row may include, for example, a plurality of end leads in a generally axial direction and a single end lead in a generally radial direction, but other arrangements (such as having two or more end leads in a radial direction) are also possible. Arranging the end leads in a row (rather than grouping them together) may allow more cooling air to contact the end leads, thereby improving cooling.

[0022] Preferably, the end leads from different coils are spaced apart from each other. This can allow air flow to pass between adjacent end leads, thereby improving cooling of the end leads and / or end windings. In addition, spacing the end leads apart from each other can improve electrical isolation.

[0023] In one embodiment of the invention, the motor is a multi-phase motor and the end leads of different phases are spaced apart from each other. In this case, embodiments of the invention can help improve the electrical separation between the phases. However, the motor can be single-phase, or have any other number of phases.

[0024] In some cases, the end leads may be placed directly on the end windings. In this case, if desired, an insulating barrier, such as a composite sheet of meta-aramid material, may be placed between the end windings and the end leads. However, in a preferred embodiment, the end leads are spaced apart from the end windings. This may allow for a passage for air flow between the end leads and the end windings, which may help cool both the end windings and the end leads.

[0025] The stator may further comprise a spacer between the end windings and the end leads. The spacer may be arranged to space the end leads from each other and / or from the end windings. Preferably, the spacer is arranged to separate the end leads from the end windings, thereby creating an air gap between the two. This may provide a path for air flow between the end windings and the end leads, thereby facilitating cooling.

[0026] The spacers may also be arranged to provide air gaps between adjacent end leads (eg in the axial direction). These air gaps may provide passages for cooling air to contact the end windings and end leads, which may help ensure effective cooling.

[0027] Preferably, the spacer is arranged to hold the end leads in position relative to each other and / or to provide electrical insulation between adjacent end leads. For example, the spacer may comprise a base and a plurality of upstanding elements. In this case, the end leads may be accommodated between adjacent upstanding members. This may allow the end leads to be held in position and / or to provide an air gap between adjacent end leads, as well as to space the end leads from the end windings.

[0028] Preferably, the base of the spacer extends in a direction substantially parallel to the axis of rotation of the motor. Preferably, the upright members extend outwardly from the base in a generally radial direction. Preferably, the upright members are arranged at spaced locations along the base.

[0029] The upright members may be arranged in pairs. The upright members in a pair of upright members may be adjacent to each other in the circumferential direction. In this case, there may be an air gap between the upright members in a pair of upright members. This may help align the end leads while allowing air to flow through the end leads between the two members of the pair. In addition, if a retaining device such as a tie or cable tie is used to hold the end leads on the end winding, the retaining device may pass between the pair of upright members. This can help ensure that the retaining device remains in place and ensures that the end leads, spacers and end windings are held together.

[0030] Preferably, the pairs of upright members are adjacent to each other in the axial direction with a gap therebetween. Preferably, the end leads are accommodated between adjacent pairs of upright members.

[0031] The base of the separator may include axial air passages. This may further aid cooling and / or reduce the amount of material used in the spacer.

[0032] Preferably, a plurality of spacers are provided between the end windings and the end leads. The spacers may be located at spaced locations circumferentially around the stator. This may help ensure that a consistent air gap is provided between the end windings and the end leads.

[0033] Preferably, a retaining device is provided for retaining the end lead on the end winding. For example, a tie or cable tie may be used to retain the end lead on the end winding. This may also help to retain the spacer in place. Thus, the spacer may be retained between the end winding and the end lead, preferably without the need for a separate mounting device.

[0034] According to another aspect of the present invention, there is provided a rotating electrical machine comprising a rotor and a stator of any form described above. The rotating electrical machine may be a motor or a generator, or both. The rotating electrical machine may include a terminal box, and some or all of the end leads may be connected to terminals in the terminal box. The connection side of the rotating electrical machine may be located at the non-driven end or the driven end, or both.

[0035] A corresponding method may also be provided. Thus, according to another aspect of the present invention, there is provided a method of manufacturing a stator for a rotating electrical machine, the method comprising the steps of: inserting a coil into a stator core so that an end winding extends out of a stator slot; and circumferentially laying out coil end leads radially outwardly around the end winding.

[0036] Features of one aspect of the invention may be provided with any other aspect. Apparatus features may have method aspects and vice versa.

[0037] In this disclosure, terms such as "radial", "axial", and "circumferential" are generally defined with reference to the axis of rotation of the rotating electrical machine, unless the context dictates otherwise. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Preferred embodiments of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:

[0039] Figure 1 shows longitudinal cross-sections through portions of a known rotating electrical machine;

[0040] Figure 2 shows a longitudinal section through a portion of the non-drive end of a known rotating electrical machine;

[0041] Figure 3 shows a longitudinal section through a portion of a rotating electrical machine in one embodiment of the invention;

[0042] Figure 4 shows portions of a stator in one embodiment of the present invention;

[0043] Figure 5 shows an end view of a stator in one embodiment of the present invention;

[0044] Fig. 6A and Figure 6B A view showing a spacer according to one embodiment of the present invention; and Figure 7 A longitudinal cross-section through parts of a rotating electrical machine in one embodiment of the invention is shown. DETAILED DESCRIPTION

[0045] Figure 1 Longitudinal sections through various parts of known rotating electrical machines are shown. A typical example is an alternator. Figure 1 , the motor includes a rotor 10 located inside a stator 12 with an air gap 14 therebetween. The rotor is mounted on a shaft 15, with the axis of rotation being indicated by a dotted line. The stator 12 includes a stator core 16 having slots extending in a generally axial direction on its inner circumference. Stator windings 17 are located in the stator slots. End windings 18 extend out of the stator slots at each end of the stator core. The end windings 18 extend around the outside of the stator core in a generally circumferential direction. The stator 12 is housed in a generally cylindrical stator frame 20. An air gap 22 is provided between the stator core 16 and the stator frame 20.

[0046] In this example, the motor is a synchronous generator, which is driven by a prime mover such as a diesel engine. A drive end adapter 24 is located at the drive end of the motor and is used to connect the motor to the prime mover. The drive end adapter 24 is bolted to the stator frame 20. A fan 26 is mounted on the shaft 15 inside the drive end adapter 24.

[0047] In operation, the fan 26 draws air flow through the motor to provide cooling. The air flow passes primarily in the axial direction through the rotor / stator air gap 14 and the stator / frame air gap 22, as shown in FIG. Figure 1 As shown by arrows 27 in FIG. For a typical motor, 70% of the air flow through the motor passes through the stator / frame air gap, while 30% of the air flow passes through the rotor / stator air gap.

[0048] Alternatively, the fan can push the air over the motor, in which case the air flow will be in the opposite direction. If desired, an external independently driven fan can be used instead of the shaft driven fan.

[0049] In such Figure 1 In electric machines such as the one shown, the stator windings typically include a plurality of coils distributed around the stator. For example, in a stator having 36 stator slots and a double layer winding, there may be a total of 36 coils. Each coil is typically formed from a single continuous conductor, such as copper wire, that is wound into a series of turns. The winding process can be performed before the coils are inserted into the stator slots or in situ. Each coil includes side windings that extend axially through the stator slots, end windings that extend from the stator slots and extend circumferentially around the ends of the stator core, and end windings for connecting the coils. For connection purposes, some or all of the coil end leads must be brought to the outside of the stator (depending on the connection method). In Figure 1 In the arrangement, the coil end leads are brought to the terminal box 23 (at Figure 1 This is accomplished by routing the coil end leads circumferentially around the stator at the non-driven end of the motor. The end leads from the individual coils in the stator winding are bundled together in a ring 30 adjacent the end winding in the axial direction.

[0050] Figure 2 A longitudinal section through a portion of the non-drive end of a known rotating electrical machine is shown, illustrating a known end lead arrangement. Figure 2 In the motor, the motor comprises a stator and a rotor substantially as described above. End leads 28 are routed circumferentially around the stator to connect the stator winding to the terminal box. End leads from different coils are bundled together in a ring 30 adjacent to the end winding 18 in the axial direction.

[0051] exist Figure 1 and Figure 2In the arrangement shown, the coil end leads are located on the non-drive end side of the motor. However, the coil end leads may also be located on the drive end side of the motor as well as or instead of the non-drive end side.

[0052] In fact, it has been found that Figure 2 Bundling the end leads together in the manner shown may result in excessive temperature increases within the end leads. Furthermore, positioning the end leads axially outside the end windings may partially restrict air flow or deflect air flow away from the end windings. This may reduce the efficiency of the cooling system. Additionally, since the end leads may carry different phases, any degradation of the insulation of the end windings may result in arcing between the end leads.

[0053] Figure 3 A longitudinal section through a portion of a rotating electrical machine is shown, conceptually illustrating the arrangement in one embodiment of the present invention. Figure 3 The motor comprises substantially the same as above with reference to Figure 1 and Figure 2 The stator and rotor described. Figure 2 As in the example of FIG. 1 , the end leads 28 are routed circumferentially around the stator to connect the stator windings to the terminal box. Figure 3 In the arrangement of FIG. 1 , the end leads 28 are not positioned adjacent to the end winding 18 in the axial direction, but are located radially outward from the end winding 18. In addition, the end leads 28 from different coils are not bundled together in a ring, but are spaced apart in rows along the outer side of the end winding in a generally axial direction. As a result, there are air gaps 37 between adjacent end leads 28. In this arrangement, an air gap 38 is also provided between the end winding 18 and the end lead 28.

[0054] According to the present invention, it has been found that Figure 3 As shown, positioning the end leads on the radially outward side of the end windings can allow more cooling air to contact the end leads. In addition, positioning the end leads away from the ends of the end windings can open up an air flow path to the fan, which can help the cooling system operate more effectively and efficiently. Cooling of the end leads is further enhanced by spacing the end leads apart. Spacing the end leads apart can also help reduce the risk of arcing. As an additional benefit, it has been found that Figure 3 The arrangement can lead to more efficient use of space.

[0055] In a preferred embodiment of the present invention, the following steps are performed when manufacturing the wound stator.

[0056] Insert the insulation paper into the stator slots

[0057] Insert the insulation paper into the slots of the stator core. The insulation paper acts as a thermal insulation layer between the copper wires and the stator core.

[0058] Preparing the Copper Coil

[0059] Copper coils are prepared by winding enameled wire on a former as per design requirements. Wire size and number of turns are selected based on design parameters. Coil shape and arrangement are selected based on the type of winding (e.g. double layer concentric, double layer lapped, etc.). The end leads of the coil remain unwound.

[0060] Insert the coil into the stator

[0061] The coils are then inserted into the stator so that they form the required polarity (eg example 4 poles) and the different phases are kept electrically 120° apart (in the case of a three phase motor).

[0062] Terminal lead connection

[0063] For connection purposes, the end leads of the coil are taken out of the stator. The number of end leads taken out depends on the connection method, parallel path, voltage requirements, etc. The end leads are routed around the outside of the winding overhang. The end leads are formed in such a way that more air can pass through the end leads and the winding overhang, which makes the cooling system more effective and efficient.

[0064] Figure 4 Several parts of a stator according to one embodiment of the present invention are shown. Figure 4 The stator comprises a stator core 16 having stator slots for accommodating stator windings. The stator windings comprise end windings 18 extending out of the stator slots and around the outside of the stator core. End leads 28 are provided, which are routed circumferentially around the outside of the end windings 18. The end leads 28 from different coils are arranged in a row in a generally axial direction and are axially spaced apart. The end leads 28 are provided with connectors 32 for connecting to terminals in a terminal box.

[0065] Figure 5 An end view of a stator in one embodiment of the present invention is shown. Figure 5 In the arrangement shown, the ends of the end leads 28 are grouped per phase, ready for connection to appropriate terminals in the terminal box. The various parameters W1, W2, L1, D1, D2 and θ are selected based on the size and design parameters of the motor.

[0066] exist Figure 4 and Figure 5In the arrangement of FIG. 1 , a plurality of spacers 34 are disposed at spaced locations around the end windings between the end windings 18 and the coil end leads 28. The spacers 34 are used to space the end leads 28 radially from the end windings 18, thereby forming an air gap 38. The spacers 34 also hold the end leads 28 in place and provide a gap between adjacent end leads. In addition, ties 36 are used to hold the end leads 28 on the end windings 18.

[0067] Fig. 6A and Figure 6B A view showing a spacer according to one embodiment of the present invention. Fig. 6A and Figure 6B The spacer 34 is designed to fit between the end winding 18 and the end lead 28 of the stator, such as Figure 4 and Figure 5 shown.

[0068] Reference Fig. 6A and Figure 6B , the spacer 34 includes a base 40 and a plurality of upright members 42. The base 40 is elongated and extends in a direction substantially parallel to the axis of rotation of the motor when the spacer is in place. The upright members 42 are arranged in pairs at spaced locations along the base.

[0069] When the spacer 34 is in place, as Figure 4 and Figure 5 As shown, the upright members 42 extend outwardly from the base 40 in a generally radial direction. The upright members in a pair of upright members are adjacent to each other in the circumferential direction, and the pair of upright members are adjacent to each other in the axial direction. The spaces 44 between adjacent pairs of upright members 42 accommodate the end leads 28, and a single end lead is generally located between two adjacent pairs of upright members (however, some duplication can be performed if desired).

[0070] Fig. 6A and Figure 6B The spacers 34 shown in the drawings form air gaps 37 between adjacent end leads 28, and air gaps 38 between the end windings 18 and the end leads 28. These air gaps provide passages for cooling air to contact the end windings and end leads, helping to ensure effective cooling. A gap 46 between a pair of upright members also assists in cooling. In addition, an axial air passage 48 may be provided through the base 40 to assist in cooling and reduce the amount of material used to form the spacers. The spacers 34 also serve to hold the end leads in place and ensure adequate electrical insulation between adjacent end leads.

[0071] exist Figure 4In the arrangement shown, a tie 36 is used to tie the end lead 28 to the end winding 18. This also clamps the spacer 34 in place without providing a separate connection point for the spacer, since the base 40 of the spacer 34 is located between the end winding 18 and the end lead 28. Although not shown, the tie can also or instead be located at the same location as the spacer and can extend between a pair of upright members.

[0072] The spacer 34 may be moulded, for example, from a temperature resistant plastic. However, any other suitable material or manufacturing technique may alternatively be used.

[0073] Figure 7 A longitudinal cross-section through portions of a rotating electrical machine in one embodiment of the invention is shown, illustrating the air flow through the machine. Figure 7 , it can be seen that air flows through the air gap 38 between the end winding 18 and the end lead 28, and then flows radially outward through the air gap 37 between adjacent end leads 28. This helps to ensure effective cooling of both the end leads and the end winding.

[0074] In tests conducted by the applicant, the temperature of the end leads was found to be reduced by 46.4 K at 400 V and 50 Hz and by 49.2 K at 480 V and 60 Hz compared to previous designs. This significant temperature reduction may allow the motor to operate more efficiently and / or allow the motor's power rating to be increased.

[0075] It should be understood that embodiments of the invention have been described by way of example only and that variations in detail may be made within the scope of the appended claims. For example, the motor may be single-phase, three-phase, or have any other number of phases. Any suitable number of coils may be used in the stator winding. The stator winding may use a variety of different winding configurations, such as concentrated, distributed, overlapping, single-layer, double-layer windings, three-layer, or any other suitable configuration. The connection side of the machine may be located at the non-driven end or the driven end, or both. Other modifications of detail will be apparent to those skilled in the art.

[0076] This application claims priority to and the benefit of UK Patent Application No. 1816855.9, filed on October 16, 2018, and U.S. Provisional Application No. 62 / 749,754, filed on October 24, 2018. The entire contents of these applications are incorporated herein by reference.

Claims

1. A stator for a rotating electric machine, the stator comprising: a stator core, the stator core comprising stator slots; as well as a plurality of stator coils, each of the stator coils including side windings located in the stator slots, end windings extending from the stator slots, and end leads for connecting the stator coils, Each stator coil is wound from a single continuous conductor and each end lead is part of the same continuous conductor as the side windings and the end windings, wherein at least some of the end leads extend circumferentially around the radially outer side of the end winding; The stator further includes a plurality of spacers between the end windings and the end leads, wherein the plurality of spacers are disposed at spaced apart locations circumferentially around the end winding, and The plurality of spacers space the end leads from the end windings in a radial direction and form an air gap in the radial direction between the end windings and the end leads.

2. The stator according to claim 1, wherein: Each stator coil is wound with conductive wires forming the side windings, the end windings, and the end leads.

3. The stator according to claim 1 or 2, wherein: The end leads are arranged in a row along the exterior of the end windings.

4. The stator according to claim 1 or 2, wherein: The end leads from different coils are spaced apart from each other.

5. The stator according to claim 1 or 2, wherein: The motor is a multi-phase motor, and end leads of different phases are spaced apart from each other.

6. The stator according to claim 1 or 2, wherein: The plurality of spacers form air gaps between adjacent end leads.

7. The stator according to claim 1 or 2, wherein: The plurality of spacers hold the end leads in place.

8. The stator according to claim 1 or 2, wherein: The plurality of spacers provide electrical isolation between adjacent end leads.

9. The stator according to claim 1 or 2, wherein: Each spacer includes a base and a plurality of upright members.

10. The stator according to claim 9, wherein: The end leads are received between adjacent upright members.

11. The stator according to claim 9, wherein: The base extends in a direction parallel to a rotation axis of the motor.

12. The stator according to claim 9, wherein: The upright members extend outwardly from the base in a radial direction.

13. The stator according to claim 9, wherein: The upright members are arranged at spaced apart locations along the base.

14. The stator according to claim 9, wherein: The upright members are arranged in pairs, and the upright members in a pair of upright members are adjacent to each other in the circumferential direction.

15. The stator according to claim 14, wherein: The pair of upright members are adjacent to each other in the axial direction.

16. The stator according to claim 9, wherein: The base includes an axial air passage.

17. The stator according to claim 1 or 2, wherein: A tie or strap is provided for retaining the end lead to the end winding, and the plurality of spacers are retained between the end winding and the end lead.

18. A rotating electric machine comprising a rotor and the stator according to claim 1 or 2.

19. A method of manufacturing a stator for a rotating electrical machine, the method comprising: inserting stator coils into stator slots in a stator core such that end windings extend out of the stator slots; circumferentially routing coil end leads radially outwardly around the end windings, wherein each stator coil is wound from a single continuous conductor and each end lead is part of the same continuous conductor as the side windings and end windings of the stator coil; and inserting a plurality of spacers at spaced locations circumferentially around the end winding, wherein the plurality of spacers space the end leads apart from the end windings in a radial direction, and The plurality of spacers form an air gap in a radial direction between the end winding and the end lead.

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