High-speed permanent magnet motor stator, motor and method with gradient insulation litz wire

Abstract

The present invention discloses a gradient insulated Litz wire, a high-speed permanent magnet motor stator, a motor and a method, and belongs to the technical field of high-speed permanent magnet motor stators; the present invention is to solve the problem that the short-circuit fault of a high-power high-speed permanent magnet motor is caused by the large inter-turn short-circuit current density, which may cause the uncertain spread of the short-circuit fault, resulting in serious consequences such as phase-to-phase short-circuit fault or even burning the motor. The gradient insulated Litz wire back winding is wound by at least one gradient insulated Litz wire, and the gradient insulated Litz wire is twisted and transposed by several enameled wires. The outer surface of each enameled wire is plated with a first insulating film, and the outer layer of the gradient insulated Litz wire is coated with a second insulating film. The material of the second insulating film is polynaphthyl ester or polyimide, and the heat resistance level of the second insulating film is one or two levels higher than that of the first insulating film of the outer layer of the enameled wire; the present invention can limit the inter-turn short-circuit fault to the faulty turn of the gradient insulated Litz wire without spreading outward, so as to realize the operation of the motor with inter-turn short-circuit fault and improve reliability.

Description

Technical Field

[0001] The invention belongs to the technical field of high-speed permanent magnet motor stators, and in particular relates to a gradient-insulated Litz wire, a high-speed permanent magnet motor stator, a motor and a method. Background Art

[0002] Surface-mounted high-speed permanent magnet synchronous motors have good prospects in the fields of aerospace generators due to their high power density, high efficiency, simple structure, high rotor mechanical strength and many other advantages. However, the presence of permanent magnets makes it impossible to demagnetize the motor when it fails. According to surveys, 80% of the motor winding failures are caused by inter-turn short circuits, especially when the motor is running in a complex environment at high altitude, there is a problem of partial discharge. In addition, the future development trends of built-in generators and high power density require the motor to run for a long time under the extreme heat resistance temperature conditions of the insulation material. Therefore, the insulation material is more prone to aging and failure, which in turn induces inter-turn short circuit failures.

[0003] At present, high-power and high-speed permanent magnet motors mainly use distributed stacked windings. In order to suppress high-frequency copper loss, the windings are usually wound in parallel with multiple strands of enameled wire. Turn-to-turn short-circuit faults usually occur between a few strands of enameled wire. The turn-to-turn short-circuit current is usually very large, which can reach several times or even dozens of times the rated current. The turn-to-turn short-circuit current density on the enameled wire with a short-circuit fault is as high as hundreds or even thousands of amperes per square millimeter. Therefore, if not handled in time, the heat generated by the high current density will cause the local temperature of the faulty enameled wire to rise rapidly, which will cause the fault to spread to the surrounding uncertainty, damage the insulation of the adjacent enameled wire, and cause more severe phase-to-phase short-circuit faults or even burn the motor. This is a difficult problem that needs to be overcome for high-power and high-speed permanent magnet motors for high-reliability applications such as aerospace.

[0004] The 2022 IEEE Transactions on Magnetics journal published "Research on Interturn Short-circuit Characteristic of the High-speed Permanent-magnet Machine with Gramme-ring Windings", which proposed that back-wound windings have a significant effect on suppressing the interturn short-circuit current of high-speed permanent magnet motors. However, since interturn short-circuit faults generally only occur between a few enameled wires at the beginning, the cross-sectional area of ​​the enameled wires used in high-speed permanent magnet motors is usually very small. Therefore, simply reducing the interturn short-circuit current cannot reduce the interturn short-circuit current density to a safe range. High interturn short-circuit current density will still induce the spread of uncertainty in interturn short-circuit faults. Summary of the invention

[0005] To this end, the present invention provides a gradient insulated Litz wire, a high-speed permanent magnet motor stator, a motor and a method. The technical problem to be solved is to reduce the inter-turn short-circuit current density of the high-power high-speed permanent magnet motor, suppress the spread of uncertainty of the inter-turn short-circuit fault, and achieve fault-tolerant operation of the motor with an inter-turn short-circuit fault, thereby improving the reliability of the motor.

[0006] In the first aspect, in order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A gradient insulated Litz wire is wound on a stator core of a high-speed permanent magnet motor in a back-wound manner, and the gradient insulated Litz wire comprises a plurality of mutually twisted and transposed enameled wires, and an outer surface of an inner core of the enameled wire is wrapped with a first insulating film;

[0008] The entire outer surface of a plurality of mutually twisted and transposed enameled wires is wrapped with a second insulating film;

[0009] The heat resistance of the second insulating film is greater than the heat resistance of the first insulating film.

[0010] Furthermore, the cross section of the gradient-insulated Litz wire is circular.

[0011] Furthermore, the overall cross-sectional area of ​​the gradient-insulated Litz wire is greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density of the motor.

[0012] Furthermore, the material of the second insulating film is one of polynaphthyl ester and polyimide.

[0013] In the second aspect, in order to solve the above technical problems, the present invention adopts the following technical solutions:

[0014] A high-speed permanent magnet motor stator comprises a stator core, wherein the inner circle and the outer circle of the stator core are respectively provided with a first tooth slot and a second tooth slot distributed axially, the conductor on one side of the coil is in the first tooth slot, and the conductor on the other side is in a second tooth slot opposite to the first tooth slot, and the coil contains at least one gradient insulated Litz wire as in the first aspect.

[0015] Furthermore, insulating plates are provided on both end side walls of the stator core.

[0016] Furthermore, slot insulation paper is laid in both the first tooth groove and the second tooth groove.

[0017] Furthermore, when the gradient-insulated Litz wire crosses from one pole of the high-speed permanent magnet motor to the next pole for coil winding, an insulating sleeve is provided on the outside of the gradient-insulated Litz wire between the two poles.

[0018] In the third aspect, in order to solve the above technical problems, the present invention adopts the following technical solutions:

[0019] A motor comprises the high-speed permanent magnet motor stator of the second aspect.

[0020] In a fourth aspect, in order to solve the above technical problems, the present invention adopts the following technical solutions:

[0021] A method for suppressing the spread of inter-turn short-circuit faults of a high-speed permanent magnet synchronous motor. Litz wire is wound on a stator core of the high-speed permanent magnet synchronous motor in a back-wound manner. The Litz wire is constructed as the gradient-insulated Litz wire of the first aspect.

[0022] Compared with the prior art, the present invention produces at least one of the following beneficial effects:

[0023] Compared with a high-speed permanent magnet synchronous motor using ordinary enameled wire or ordinary Litz wire back-wound winding, when an inter-turn short circuit fault occurs between a few enameled wires in the gradient-insulated Litz wire back-wound winding of the present invention, since the heat resistance of the second insulating film on the outer layer of the gradient-insulated Litz wire is higher than that of the first insulating film on the enameled wire, the abnormal heating caused by the inter-turn short circuit current will first damage the first insulating film of the enameled wire inside the gradient-insulated Litz wire where the fault occurs, and since the total cross-sectional area of ​​the faulty enameled wire increases, the inter-turn short circuit current density flowing through it and the heating thereof are greatly reduced;

[0024] The cross-sectional area of ​​the gradient insulated Litz wire is greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density, so that the average inter-turn short-circuit current density of the faulty gradient insulated Litz wire can be reduced to within the rated current density range, and the heat generation of the gradient insulated Litz wire with an inter-turn short-circuit fault can be reduced to within an allowable range; the inter-turn short-circuit fault can be limited to the gradient insulated Litz wire, and will no longer spread further to the adjacent non-faulty gradient insulated Litz wire, so that the motor can operate with an inter-turn short-circuit fault, thereby improving reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to explain the present invention more clearly, the following briefly describes the drawings required for use in the implementation cases or prior art descriptions. The drawings described herein are used to provide a further understanding of the present invention and do not constitute an improper limitation on the present invention.

[0026] Figure 1 It is a structural schematic diagram of a high-speed permanent magnet motor stator with a gradient-insulated Litz wire back winding;

[0027] Figure 2 for Figure 1 sectional view of;

[0028] Figure 3 It is the structural diagram of the insulation board;

[0029] Figure 4 It is a structural diagram of a single-phase gradient-insulated Litz wire back winding inserted in the stator core slots;

[0030] Figure 5 for Figure 4 Schematic diagram of a single-phase gradient-insulated Litz wire winding;

[0031] Figure 6 This is a structural diagram of a gradient insulated Litz wire;

[0032] Figure 7 This is a structural diagram of the twisting and transposition twisting of the enameled wire in the gradient insulated Litz wire;

[0033] In the figure: 1, stator core, 10, first tooth slot, 11, second tooth slot, 2, gradient insulated Litz wire back-wound winding, 21, winding lead, 22, insulating sleeve, 23, coil, 3, slot wedge, 4, slot insulation paper, 5, insulating plate, 50, side slot, 6, gradient insulated Litz wire, 61, inner core, 62, first insulating film, 63, second insulating film. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0035] Example 1

[0036] like Figure 6 and Figure 7 As shown, there is a gradient insulated Litz wire 6, which is back-wound on the stator core 1 of the high-speed permanent magnet motor. The gradient insulated Litz wire 6 includes a plurality of mutually twisted and transposed enameled wires, and the outer surface of the inner core 61 of the enameled wire is wrapped with a first insulating film 62;

[0037] The entire outer surface of the plurality of mutually twisted and transposed enameled wires is wrapped with a second insulating film 63;

[0038] The heat resistance of the second insulating film 63 is greater than the heat resistance of the first insulating film 62 .

[0039] At this time, when an inter-turn short circuit fault occurs between a few enameled wires belonging to different turns, a very high inter-turn short circuit current density will be generated in the enameled wire where the first insulating film 62 is damaged. The high inter-turn short circuit current density will cause the temperature of the faulty enameled wire to rise rapidly, and the heat will be transferred to the surrounding enameled wires. When the heat resistance level of the first insulating film 62 is exceeded, the first insulating film 62 of the surrounding enameled wires will be damaged. Since the enameled wires in different strands of gradient insulated Litz wires are separated by the second insulating film 63, and the insulation level of the second insulating film 63 is higher than that of the first insulating film 62 of the enameled wires, the abnormal heating of the faulty enameled wire will first damage the enameled wire in the gradient insulated Litz wire of the strand where the fault is located. As the fault progresses, the cross-sectional area of ​​the faulty enameled wire continues to increase, causing the inter-turn short circuit current density to continue to decrease, thereby reducing the heating of the enameled wire caused by the inter-turn short circuit fault.

[0040] Of course, in some disclosures, the overall cross-sectional area of ​​the gradient-insulated Litz wire is greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density of the motor; when the fault progresses to a short circuit between all the enameled wires of the gradient-insulated Litz wire, if the cross-sectional area of ​​the gradient-insulated Litz wire is designed to be greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density of the motor, the average inter-turn short-circuit current density of the faulty gradient-insulated Litz wire can be reduced to within the rated current density range, that is, the temperature is reduced to within the allowable range, thereby limiting the fault to the gradient-insulated Litz wire and no longer spreading outward, thereby realizing the operation of the high-speed permanent magnet synchronous motor with an inter-turn short-circuit fault and improving the reliability of the motor.

[0041] The gradient insulated Litz wire 6 includes several enameled wires that are twisted and transposed with each other. It can be understood as an existing finished product. For example, the current existing finished product insulated Litz wire is made of several enameled wires that are twisted and transposed with each other. In the application, no improvement is made here. Of course, in the process of twisting and transposing the existing enameled wires, the length error of each enameled wire is guaranteed to be less than 1%. At present, the inner core 61 of the enameled wire is often selected as a copper core.

[0042] The first insulating film 62 of the enameled wire should meet the heat resistance requirements of the motor during long-term normal operation, that is, the heat resistance grade of the appropriate insulating material should be selected according to the long-term operating temperature of the motor, such as the selected heat resistance grade F; the second insulating film 63 of the outer layer of the gradient insulated Litz wire 6 has a higher heat resistance grade than the first insulating film 62 of the enameled wire, such as the grade of the second insulating film 63 corresponding to the grade of the first insulating film 62, and the grade selected for the second insulating film 63 is H or C; of course, according to actual needs, the material of the second insulating film 63 can be selected as polynaphthyl ester or polyimide.

[0043] Optionally, the cross section of the gradient insulated Litz wire 6 is circular. As required, if the cross-sectional area of ​​the gradient insulated Litz wire 6 is greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density of the motor, and the number of enameled wires of the gradient insulated Litz wire 6 is too large, and the structure of the bonded wire obtained by twisting and transposing once is unreasonable, it can be twisted and transposed twice, that is, several twisted and transposed strands are twisted and transposed again for bonding.

[0044] Of course, sometimes in order to better adapt to the stator core 1, the first tooth slots 10 and the second tooth slots 11 of the inner circle and the outer circle of the existing stator core 1 can replace the "T"-shaped slots with rectangular slots; at this time, the cross-sectional profile of the gradient insulated Litz wire 6 is pressed into a rectangle.

[0045] Example 2

[0046] like Figures 1 to 5As shown, a high-speed permanent magnet motor stator includes a stator core 1, the inner circle and outer circle of the stator core 1 are respectively provided with axially distributed first tooth slots 10 and second tooth slots 11, the conductor on one side of the coil 23 is in the first tooth slot 10, and the conductor on the other side is in the second tooth slot 11 opposite to the first tooth slot 10, and the coil 23 contains at least one strand of gradient insulated Litz wire as in Example 1.

[0047] In practice, if the stator core 1 is made of silicon steel sheets or iron-cobalt alloy sheets by wire cutting, the inner and outer circles of the stator core 1 are cut into "T"-shaped slots, such as the first slots 10 and the second slots 11 forming "T"-shaped slots; the first slots 10 and the second slots 11 on the inner and outer circles of the stator core 1 can be designed to have different numbers of slots, but the number of second slots 11 on the inner circle should be an integer multiple of the number of first slots 10 on the outer circle. Preferably, the number of second slots 11 on the inner circle should be equal to the number of first slots 10 on the outer circle. The number of slots per pole and per phase is an integer, and the laminations of the stator core 1 are bonded with high-temperature epoxy resin, or welds are machined at the center of the outer circle teeth for welding and fixing, or circular holes are machined on the outer teeth for riveting and fixing.

[0048] The insulating plate 5 is provided with side grooves 50 that are matched with the first tooth grooves 10 and the second tooth grooves 11 one by one. The material of the insulating plate 5 is preferably an epoxy plate. When the stator is assembled, the two insulating plates 5 are bonded to the two ends of the stator core 1 by epoxy resin to ensure the insulation between the winding ends and the core. The slot insulation paper 4 is laid in the slot of the stator core 1 to ensure the insulation between the winding in the slot and the core.

[0049] by Figure 4 For example, at least one gradient insulated Litz wire 6 is put together, first inserted into the first tooth slot 10 of the first slot of the stator core 1, then wound around the stator core 1, inserted into the second tooth slot 11 of the first slot of the stator core 1, then wound around the stator core 1, inserted into the first tooth slot 10 of the first slot of the stator core 1, and so on, until the winding of the first coil 23 of the back winding is completed, and then the wire directly crosses into the next slot of the stator core No. 2 slot to continue winding, and completes the winding of the coil 23 in the No. 2 slot. When crossing to the next pole of the motor to wind the coil 23, it is also necessary to cover the outer side of the wire with an insulating sleeve 22. For example, when the coil 23 in the No. 2 slot crosses to the No. 13 slot to continue winding, the outer side of several gradient insulated Litz wires 6 is covered with an insulating sleeve 22. When all the coils 23 belonging to the same phase are wound, the winding of the phase winding is completed. That is, different series-connected coils 23 belonging to the same-phase winding are wound continuously without interruption, which avoids the welding between the leads of different coils 23 to produce insulation weak points.

[0050] The winding is led out by a lead wire 21 and connected to an external power supply or a motor controller. Slot wedges 3 are inserted into the inner and outer circular slots of the stator core 1, and insulating varnish is impregnated between the insulating Litz wires with different gradients.

[0051] Compared with the high-speed permanent magnet synchronous motor using ordinary enameled wire or ordinary Litz wire back-wound winding, when the gradient insulated Litz wire back-wound winding 2 of the present invention has an inter-turn short circuit fault between a few enameled wires, since the insulation level of the second insulating film 63 of the outer layer of the gradient insulated Litz wire is higher than the first insulating film 62 of the enameled wire, the abnormal heat caused by the inter-turn short circuit current will first damage the first insulating film of the enameled wire inside the gradient insulated Litz wire where the fault occurs, and since the total cross-sectional area of ​​the faulty enameled wire increases, the inter-turn short circuit current density flowing through it and the heat generated by it are greatly reduced;

[0052] Alternatively, the cross-sectional area of ​​the gradient insulated Litz wire is greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density. When the fault progresses to a short circuit between all enameled wires of the gradient insulated Litz wire, the average inter-turn short-circuit current density of the faulty gradient insulated Litz wire can be reduced to within the rated current density range, and the heat generation of the gradient insulated Litz wire with the inter-turn short-circuit fault can be reduced to within the allowable range. The inter-turn short-circuit fault can be limited to the gradient insulated Litz wire, and will no longer spread further to the adjacent non-faulty gradient insulated Litz wire, so that the motor can operate with an inter-turn short-circuit fault, thereby improving reliability.

[0053] Example 3

[0054] A motor, comprising a high-speed permanent magnet motor stator of embodiment 2; compared with a high-speed permanent magnet synchronous motor using an ordinary enameled wire or an ordinary Litz wire back-wound winding, when a turn-to-turn short circuit fault occurs between a few enameled wires in the gradient-insulated Litz wire back-wound winding 2 of the present invention, since the insulation level of the second insulating film 63 of the outer layer of the gradient-insulated Litz wire is higher than the first insulating film 62 of the enameled wire, the abnormal heating caused by the turn-to-turn short circuit current will first damage the first insulating film of the enameled wire inside the gradient-insulated Litz wire where the fault occurs, and since the total cross-sectional area of ​​the faulty enameled wire is increased, the turn-to-turn short circuit current density flowing through it and the heating thereof are greatly reduced;

[0055] Alternatively, the cross-sectional area of ​​the gradient insulated Litz wire is greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density. When the fault progresses to a short circuit between all enameled wires of the gradient insulated Litz wire, the average inter-turn short-circuit current density of the faulty gradient insulated Litz wire can be reduced to within the rated current density range, and the heat generation of the gradient insulated Litz wire with the inter-turn short-circuit fault can be reduced to within the allowable range. The inter-turn short-circuit fault can be limited to the gradient insulated Litz wire, and will no longer spread further to the adjacent non-faulty gradient insulated Litz wire, so that the motor can operate with an inter-turn short-circuit fault, thereby improving reliability.

[0056] Example 4

[0057] A method for suppressing the spread of inter-turn short-circuit faults of a high-speed permanent magnet synchronous motor. Litz wire varnish is wound on a stator core 1 of the high-speed permanent magnet motor in a back-wound manner. The Litz wire varnish is constructed as a gradient-insulated Litz wire 6 as in Example 1.

[0058] Compared with the high-speed permanent magnet synchronous motor using ordinary enameled wire or ordinary Litz wire back-wound winding, when the gradient insulated Litz wire back-wound winding 2 of the present invention has an inter-turn short circuit fault between a few enameled wires, since the insulation level of the second insulating film 63 of the outer layer of the gradient insulated Litz wire is higher than the first insulating film 62 of the enameled wire, the abnormal heat caused by the inter-turn short circuit current will first damage the first insulating film of the enameled wire inside the gradient insulated Litz wire where the fault occurs, and since the total cross-sectional area of ​​the faulty enameled wire increases, the inter-turn short circuit current density flowing through it and the heat generated by it are greatly reduced;

[0059] Alternatively, the cross-sectional area of ​​the gradient insulated Litz wire is greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density. When the fault progresses to a short circuit between all enameled wires of the gradient insulated Litz wire, the average inter-turn short-circuit current density of the faulty gradient insulated Litz wire can be reduced to within the rated current density range, and the heat generation of the gradient insulated Litz wire with the inter-turn short-circuit fault can be reduced to within the allowable range. The inter-turn short-circuit fault can be limited to the gradient insulated Litz wire, and will no longer spread further to the adjacent non-faulty gradient insulated Litz wire, so that the motor can operate with an inter-turn short-circuit fault, thereby improving reliability.

[0060] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only for illustrating the specific implementation methods of the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solutions of the present invention in accordance with the technical ideas proposed by the present invention should be included in the protection scope of the present invention.

Claims

1. A gradient-insulated Litz wire, wherein the gradient-insulated Litz wire (6) is wound on a stator core (1) of a high-speed permanent magnet motor in a back-wound manner, wherein the gradient-insulated Litz wire (6) comprises a plurality of mutually twisted and transposed enameled wires, and wherein: The outer surface of the inner core (61) of the enameled wire is coated with a first insulating film (62); The entire outer surface of a plurality of mutually twisted and transposed enameled wires is wrapped with a second insulating film (63); The heat resistance of the second insulating film (63) is greater than the heat resistance of the first insulating film (62); The overall cross-sectional area of ​​the gradient-insulated Litz wire (6) is greater than or equal to the quotient of the inter-turn short-circuit current and the rated current density of the high-speed permanent magnet motor.

2. The gradient-insulated litz wire according to claim 1, characterized in that: Litz wire with gradient insulation has a circular cross section.

3. The gradient insulated Litz wire according to claim 1, characterized in that: The material of the second insulating film (63) is one of polynaphthyl ester and polyimide.

4. A high-speed permanent magnet motor stator, comprising a stator core (1), wherein the inner circle and the outer circle of the stator core (1) are respectively provided with axially distributed first tooth slots (10) and second tooth slots (11), characterized in that: The conductor on one side of the coil (23) is in the first tooth slot (10), and the conductor on the other side is in the second tooth slot (11) opposite to the first tooth slot (10). The coil (23) contains at least one strand of gradient-insulated Litz wire (6) as claimed in any one of claims 1 to 3.

5. The high-speed permanent magnet motor stator according to claim 4, characterized in that: Insulation plates (5) are provided on both end side walls of the stator core (1).

6. The high-speed permanent magnet motor stator according to claim 4, characterized in that: Groove insulation paper (4) is laid in both the first tooth groove (10) and the second tooth groove (11).

7. The high-speed permanent magnet motor stator according to claim 4, characterized in that: When the gradient-insulated Litz wire crosses from one pole of the high-speed permanent magnet motor to the next pole to wind the coil (23), an insulating sleeve (22) is provided on the outside of the gradient-insulated Litz wire between the two poles.

8. A motor, characterized in that: Including the high-speed permanent magnet motor stator as described in claim 4.

9. A method for suppressing the spread of inter-turn short-circuit faults in high-speed permanent magnet synchronous motors, characterized in that: The Litz wire is wound on a stator core (1) of a high-speed permanent magnet motor in a back-wound manner, and the Litz wire is constructed as a gradient-insulated Litz wire as claimed in any one of claims 1 to 3.

Images