Electric motor with separation partition wall structure to enable direct immersion cooling of stator end winding

Abstract

Provided is an electric motor with a separation partition wall structure to enable direct immersion cooling of stator end winding. According to an embodiment of the present invention, the electric motor comprises: a stator fixed inside a housing to form a rotating magnetic field for driving a rotor; the rotor configured to rotate inside the stator by interacting with the magnetic field formed by the stator; and a refrigerant flow unit for immersing and cooling the end winding of the stator by circulating a refrigerant inside the housing. Accordingly, the end winding portion of the stator may be separated by the partition wall structure to be immersed and cooled in a nonconductive working fluid, thereby achieving high heat dissipation performance for the end winding of the stator having high heat loss characteristics and improving the cooling uniformity of the stator.

Description

Motor capable of direct liquid immersion cooling of the stator end windings through a separating bulkhead structure

[0001] The present invention relates to heat dissipation of an electric motor, and more specifically, to an electric motor having a structure capable of more effectively cooling a stator winding portion located in a position unfavorable to heat transfer of the electric motor.

[0002] In most synchronous motors capable of variable speed control using inverters, the ratio of copper loss to iron loss varies depending on the driving characteristics of each operating range, and heat proportional to the losses is continuously generated within the motor. The stator's end windings are thermally vulnerable as they have a relatively lower allowable temperature compared to the iron core; since excessive heat locally accumulated in these end windings is a major cause of reduced output, decreased efficiency, and ultimately shortened lifespan, intensive thermal management is required to improve motor performance.

[0003] Figure 1 is a diagram showing the characteristics of conventional electric motor cooling methods. Depending on the working fluid, the cooling methods for electric motors are typically: 1) air cooling using forced convection, 2) water cooling by flowing cooling water through the housing or internal components, and 3) oil cooling by directly injecting oil into the internal heat source of the motor.

[0004] Since air cooling utilizes a fluid (air) with a relatively low heat capacity, it is difficult to expect high heat dissipation performance; while water cooling offers improved cooling performance compared to air cooling, high efficiency cannot be expected because it is an indirect cooling method where cooling water flows through spiral channels inside the housing wall, transferring heat generated in the windings sequentially through the iron core and housing wall to the refrigerant.

[0005] Figure 2 illustrates a conventional electric motor oil cooling structure. As shown, in the electric motor, the flow space where the stator end winding is located is not separated from the rotor space. Consequently, the cooling fluid primarily cools the end winding through the oil channels, and as it descends due to gravity, it exhibits a flow pattern that is scattered by the rotational motion of the shaft. Consequently, there is a problem where the cooling performance becomes non-uniform due to the irregular flow of the cooling fluid, in addition to the cooling performance itself. This is confirmed by the simulation results (Figure 3) and experimental results (Figure 4) regarding the non-uniformity characteristics of the electric motor's oil cooling performance. Thus, although the oil cooling method employs a direct cooling technique in which cooling fluid is directly injected into the iron core and windings—the main sources of heat generation inside the housing—it has the disadvantage of poor cooling uniformity.

[0006] Furthermore, as continuous demands for improvement and interest in miniaturization and high output continue to grow, it is also a time when a new structure for cooling technology is required to overcome the limitations of the electric motor's electromagnetic characteristics.

[0007] The present invention has been devised to solve the above-mentioned problems, and the objective of the present invention is to provide an electric motor that implements high heat dissipation performance for the end winding of a stator having high heat loss characteristics and reinforces the cooling efficiency of the end winding to improve the cooling uniformity of the stator by separating the end winding into a partition structure and immersing it with a non-conductive working fluid.

[0008] An electric motor according to one embodiment of the present invention for achieving the above objective includes: a stator fixed inside a housing and forming a rotating magnetic field for driving a rotor; a rotor that rotates by interacting with a magnetic field formed by the stator inside the stator; and a refrigerant flow section that immerses and cools the end winding of the stator by flowing a refrigerant inside the housing.

[0009] The electric motor according to the present invention may further include a partition structure for separating the space where the end winding is located.

[0010] The bulkhead structure may include a first bulkhead that separates the space where the end winding is located from the space where the rotor is located.

[0011] The first bulkhead may be a cylindrical bulkhead joined to the inner circle of the end winding.

[0012] The bulkhead structure may further include a second bulkhead that separates the space where the end winding is located from the space where the stator core and the internal winding are located.

[0013] The second bulkhead may be a ring-shaped bulkhead joined to the iron core-opposing surface of the end winding.

[0014] The second bulkhead has radially formed slots for accommodating internal windings, and its lower end may be joined to a cylindrical bulkhead.

[0015] The refrigerant may be a non-conductive working fluid.

[0016] According to another aspect of the present invention, a cooling device for an electric motor is provided, comprising: an inlet for introducing a refrigerant into a refrigerant flow space; an outlet for discharging the refrigerant that has flowed through the refrigerant flow space; and a partition structure that forms a refrigerant flow space together with a housing of an electric motor, wherein the end winding of the electric motor is immersed in the refrigerant flow space.

[0017] According to another aspect of the present invention, a method for cooling an electric motor is provided, comprising the steps of: introducing a refrigerant into a refrigerant flow space; immersing and cooling the end winding of the electric motor in the refrigerant flow space; discharging the refrigerant that has flowed through the refrigerant flow space; and wherein the refrigerant flow space is formed by the housing of the electric motor and a bulkhead structure.

[0018] As described above, according to the embodiments of the present invention, by separating the end winding portion of the stator with a partition structure and cooling it by immersion in a non-conductive working fluid, high heat dissipation performance can be achieved for the end winding of the stator, which has high heat loss characteristics, thereby improving the uniformity of cooling of the stator.

[0019] In addition, according to embodiments of the present invention, the end winding, which is the main source of heat generation, can be directly immersed in a low-temperature refrigerant without interfering with electromagnetic phenomena between the iron core of the stator and the end winding, thereby improving cooling performance and simplifying secondary cooling equipment, and ultimately increasing the efficiency and lifespan of the motor due to the increased cooling effect.

[0020] FIG. 1 is a diagram showing the characteristics of a conventional electric motor cooling method for electric vehicles.

[0021] FIG. 2 is a drawing illustrating a conventional electric motor oil cooling structure.

[0022] Figure 3 shows the results of simulating the non-uniform oil cooling performance characteristics of the electric motor.

[0023] Figure 4 shows the experimental results of the non-uniform oil cooling performance characteristics of the electric motor.

[0024] FIG. 5 is an external perspective view of a synchronous motor according to one embodiment of the present invention,

[0025] FIG. 6 is a cross-sectional view of a synchronous motor according to one embodiment of the present invention,

[0026] FIG. 7 is a diagram showing the situation of refrigerant flow in the refrigerant flow section.

[0027] FIG. 8 is a cross-sectional view of a synchronous motor configured excluding the refrigerant flow section,

[0028] FIG. 9 is a drawing showing the vertical bulkhead and the cylindrical bulkhead enlarged from a different angle.

[0029] FIG. 10 is a drawing showing the vertical bulkhead and the cylindrical bulkhead separated together with the end winding and the internal winding.

[0030] Figure 11 is a drawing showing the vertical bulkhead viewed from the front, along with the internal winding and the cylindrical bulkhead.

[0031] The present invention will be described in more detail below with reference to the drawings.

[0032] An embodiment of the present invention provides an electric motor capable of direct liquid immersion cooling of the stator separation windings using a separation partition structure. This is a technology that physically separates the space of the stator separation windings of the motor from the space of other components using a separation partition structure, thereby cooling the end windings of the stator, which are located in a position unfavorable for heat transfer, by immersion (liquid immersion) with a non-conductive working fluid.

[0033] FIGS. 5 and FIGS. 6 are an external perspective view and a cross-sectional view of a synchronous motor according to an embodiment of the present invention. FIG. 6 shows the synchronous motor shown in FIG. 5 with the outer housing (110) removed and the synchronous motor cut along the length of the rotation axis (140).

[0034] As described above, a synchronous motor according to an embodiment of the present invention comprises an inner housing (115), a stator (120), a rotor (130), a rotating shaft (140), and a refrigerant flow section (150).

[0035] The inner housing (115) forms a space in which the internal components of the synchronous motor are arranged, and together with the outer housing (110) shown in FIG. 5, forms the housing of the synchronous motor.

[0036] The stator (120) is fixed inside the inner housing (115) and is configured to form a rotating magnetic field to drive the rotor (130), and consists of an end winding (121), an inner winding (122), and an iron core (123).

[0037] The inner winding (122) is the winding portion inserted into the slot of the iron core (123), and the end winding (121) is the winding portion that is out of the slot. In the embodiment of the present invention, since the cooling of the end winding (121) is important, the winding of the stator (120) is divided into the end winding (121) and the inner winding (122).

[0038] The rotor (130) rotates by interacting with the magnetic field formed by the stator (120) inside the stator (120), ultimately rotating the rotation axis (140) which is fixedly connected to itself.

[0039] The refrigerant flow section (150) is configured to form a space for flowing refrigerant in the internal space of the inner housing (110) to immerse the end winding (121) of the stator (120) in liquid cooling.

[0040] A non-conductive working fluid with excellent insulation properties is used as the refrigerant so as not to affect the electromagnetic phenomena of the windings (121, 122) and the iron core (122) of the stator (120).

[0041] In addition, the refrigerant flow space of the refrigerant flow section (150) is configured to include only the end winding (121), so that only the end winding (121) is immersed in liquid. That is, the refrigerant flow space of the refrigerant flow section (150) is formed so as not to include the internal winding (122) and iron core (123) of the stator (120) as well as the rotor (130).

[0042] That is, in addition to the stator (120) and rotor (130) being spatially separated by the refrigerant flow space of the refrigerant flow section (150), the end winding (121) of the stator (120) is also spatially separated from the internal winding (122) and iron core (123) of the stator (120).

[0043] This allows the liquid immersion cooling of the refrigerant flow section (150) to be concentrated on the end winding (121). FIG. 7 shows a situation in which refrigerant (indicated in dark black) flows in the refrigerant flow section (150). As illustrated, it can be seen that the only component immersed by the refrigerant is the end winding (121). That is, the inner winding (122) and the iron core (123) are not subject to liquid immersion cooling by the refrigerant flow section (150), and thus the inner winding (122) and the iron core (123) are not in the refrigerant flow path.

[0044] A refrigerant flow section (150) that performs such a function is configured to include a refrigerant inlet section (151), a vertical partition (152), a cylindrical partition (153), and a refrigerant outlet section (154), as illustrated.

[0045] For reference, FIG. 8 shows the configuration of a synchronous motor excluding the components corresponding to the refrigerant flow section (150) shown in FIG. 6. Comparing FIG. 6 with FIG. 8 can help in understanding how the refrigerant flow space is created by the refrigerant flow section (150), how the stator (120) and the rotor (130) are spatially separated by the refrigerant flow section (150), and how the end winding (121) of the stator (120), the internal winding (122) of the stator (120), and the iron core (123) are spatially separated by the refrigerant flow section (150).

[0046] As shown in FIGS. 6 and 7, the refrigerant inlet (151) is where the refrigerant flows into the internal space of the refrigerant flow section (150), and the refrigerant outlet (154) is where the refrigerant that has flowed through the internal space of the refrigerant flow section (150) flows out.

[0047] The vertical partition (152) and the cylindrical partition (153) are configured to form a refrigerant flow space of the refrigerant flow section (150) inside the inner housing (115). In FIG. 9, the vertical partition (152) and the cylindrical partition (153) are shown enlarged at an angle that allows for better observation, and in FIG. 10, the vertical partition (152) and the cylindrical partition (153) are shown separated from the end winding (121) and the inner winding (122) in a synchronous motor according to an embodiment of the present invention, and in FIG. 11, the vertical partition (152) is shown viewed from the front along with the inner winding (122) and the cylindrical partition (153).

[0048] As can be seen from the drawings, the cylindrical partition (153) is a cylindrical partition (excluding the upper and lower surfaces) joined to the inner circular portion of the end winding (121). The cylindrical partition (153) separates the space where the end winding (121) is located from the space where the rotor (130) is located.

[0049] The vertical partition (152) is a ring-shaped partition joined to the opposite surface where the end winding (121) faces the iron core (123). The vertical partition (152) separates the space where the end winding (121) is located from the space where the inner winding (122) and the iron core (123) are located.

[0050] Meanwhile, as can be seen from FIGS. 10 and 11, slots for accommodating internal windings (122) are formed radially in the vertical bulkhead (152), and the lower end of the vertical bulkhead (152) is joined to the cylindrical bulkhead (153).

[0051] Up to now, preferred embodiments of an electric motor capable of direct liquid immersion cooling of the stator end windings using a separating bulkhead structure have been described in detail.

[0052] In the above embodiment, the end winding portion of the stator is separated by a partition structure and immersed in a non-conductive working fluid for cooling, thereby achieving high heat dissipation performance for the end winding of the stator, which has high heat loss characteristics, and improving the uniformity of cooling of the stator.

[0053] In addition, in the above embodiment, the end winding, which is the main source of heat generation, can be directly immersed in a low-temperature refrigerant without interfering with electromagnetic phenomena between the stator core and the end winding, thereby improving cooling performance and simplifying the secondary cooling equipment, and ultimately increasing the efficiency and lifespan of the motor due to the increased cooling effect.

[0054] In particular, since only the stator end windings are directly immersed in a low-temperature liquid, it overcomes the disadvantage of non-uniform cooling inherent in conventional oil cooling methods and improves upon the low performance of indirect cooling methods using conventional water-cooling jackets, thus it is expected to become a new cooling solution for high output and lightweight design.

[0055] Meanwhile, it is also possible to implement only some of the configurations of the electric motor presented in the above embodiment. Specifically, it is possible to implement only the refrigerant flow section (150) configured to include a refrigerant inlet section (151), a vertical partition (152), a cylindrical partition (153), and a refrigerant outlet section (154), and in this case, the technical concept of the present invention may also be applied.

[0056] Furthermore, although preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above. Various modifications are possible by those skilled in the art without departing from the essence of the invention as claimed in the claims, and such modifications should not be understood individually from the technical spirit or perspective of the present invention.

Claims

1. A stator fixed inside a housing and forming a rotating magnetic field to drive a rotor; A rotor that rotates by interacting with a magnetic field formed by the stator inside the stator; An electric motor characterized by including a refrigerant flow section that flows a refrigerant inside a housing to liquid-immerse and cool the end winding of a stator.

2. In Claim 1, An electric motor characterized by further including a bulkhead structure for separating the space where the end winding is located.

3. In Claim 2, The bulkhead structure is, An electric motor characterized by including a first partition that separates the space where the end winding is located from the space where the rotor is located.

4. In Claim 3, The first bulkhead is, An electric motor characterized by a cylindrical partition joined to the inner circle of the end winding.

5. In Claim 2, The bulkhead structure is, An electric motor characterized by further including a second partition that separates the space where the end winding is located from the space where the stator core and the internal winding are located.

6. In Claim 5, The second bulkhead is, An electric motor characterized by a ring-shaped partition joined to the iron core opposite surface of the end winding.

7. In Claim 6, The second bulkhead is, Slots for accommodating internal windings are formed radially, and An electric motor characterized by having its lower end joined to a cylindrical bulkhead.

8. In Claim 1, The refrigerant is, An electric motor characterized by being a non-conductive working fluid.

9. An inlet for introducing refrigerant into the refrigerant flow space; An outlet for discharging the refrigerant that has flowed through the refrigerant flow space; and A bulkhead structure forming a refrigerant flow space together with the electric motor housing; including In the refrigerant flow space, A cooling device for an electric motor characterized by the immersion cooling of the end winding of the electric motor.

10. A step of introducing refrigerant into the refrigerant flow space; A step of immersing and cooling the end winding of the motor in a refrigerant flow space; A step of discharging the refrigerant that has flowed through the refrigerant flow space; and The refrigerant flow space is, A method for cooling an electric motor characterized by being formed by the housing and bulkhead structure of the electric motor.

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