High speed permanent magnet motor with reduced back emf

Abstract

The application relates to a high-speed permanent magnet motor with reduced counter electromotive force, which comprises a shell, a stator assembly arranged in the shell, the stator assembly comprising a stator core and coil windings, a rotating shaft channel being formed in the middle of the stator core, a plurality of winding grooves being arranged in the stator core in the circumferential direction and being arranged in the axial direction of the stator core, each winding groove being provided with coil windings, the stator core comprising a main magnetic field core and a voltage reduction circuit core, the main magnetic field core and the voltage reduction circuit core being magnetically connected, the winding groove corresponding to the main magnetic field core being open at one end of the shaft of the stator core, and the winding groove corresponding to the voltage reduction circuit core being closed at one end of the shaft of the stator core; and a rotor assembly arranged in the rotating shaft channel and rotating with the rotating shaft, the rotor assembly comprising a rotating shaft and a plurality of permanent magnets rotating with the rotating shaft, the permanent magnets being arranged in the region of the rotating shaft opposite to the main magnetic field core.

Description

Technical Field

[0001] The present invention relates to the field of high-speed permanent magnet motors, and in particular to a high-speed permanent magnet motor capable of reducing reverse electromotive force. Background Art

[0002] Permanent magnet motors are increasingly widely used in the machine tool industry. Their "hard torque," high power density, and rapid torque response make them particularly popular in applications such as rapid starting and stopping, drilling and tapping, and zero-speed shaft locking. Furthermore, their high power density significantly reduces the size and weight of comparable asynchronous motors while achieving comparable performance.

[0003] Permanent magnet motors contain permanent magnets, allowing the motor rotor to generate a large magnetic flux in the no-current state. However, the permanent magnetic field linearly increases the back EMF as the rotor speed increases. As the speed increases, the back EMF increases linearly, eventually reaching the bus voltage limit. To meet the target speed, the only option is to weaken the magnetic field strength to reduce the back EMF. Therefore, an additional demagnetizing current is applied to the motor to weaken the air gap flux density, thereby reducing the back EMF and allowing the motor to increase speed further. Therefore, during the field weakening speed-up process of a permanent magnet motor, increasing current is consumed as the speed increases. Consequently, higher speeds require greater demagnetization current. This increased demagnetization current increases the rotor's high iron loss, which in turn increases the magnet temperature, ultimately leading to motor degradation or burnout.

[0004] In the prior art, in order to solve the above problems, a variable magnetic flux design is generally adopted, for example, the permanent magnets in the motor are set to a movable structure, or the arrangement of the permanent magnets is changed, etc. However, its structure is complex and the effect of reducing the back electromotive force is limited.

[0005] The purpose of the present invention is to design a high-speed permanent magnet motor that reduces the back electromotive force in order to solve the above problems in the prior art. Summary of the Invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention provides a high-speed permanent magnet motor with reduced back electromotive force, which can effectively solve at least one problem existing in the above-mentioned prior art.

[0007] The technical solution of the present invention is:

[0008] A high-speed permanent magnet motor for reducing back electromotive force, comprising:

[0009] case;

[0010] The stator assembly is disposed inside the housing and includes a stator core and coil windings. A rotating shaft channel is formed in the middle of the stator core. The stator core is provided with a plurality of winding slots spaced apart along the circumference. The winding slots are provided through the stator core in the axial direction. Each winding slot is provided with a coil winding. The stator core includes a main magnetic field core and a step-down circuit core. The main magnetic field core and the step-down circuit core are magnetically connected. The winding slots corresponding to the main magnetic field core are open at one end toward the axis of the stator core, and the winding slots corresponding to the step-down circuit core are closed at one end toward the axis of the stator core.

[0011] The rotor assembly penetrates and rotates in the shaft channel. The rotor assembly includes a shaft and a plurality of permanent magnets that rotate with the shaft. The permanent magnets are arranged in the area of ​​the shaft facing the main magnetic field core.

[0012] Furthermore, the main magnetic field core and the step-down circuit core are both composed of a plurality of stacked steel plates, and the main magnetic field core and the step-down circuit core are arranged in contact with each other.

[0013] Furthermore, the thickness ratio of the main magnetic field core and the step-down circuit core is 6:0.5~2.

[0014] Furthermore, the step-down circuit core includes a step-down circuit outer core and a step-down circuit inner core. The cross-section of the step-down circuit outer core is the same as the cross-section of the main magnetic field core. The step-down circuit inner core closes the opening of the winding slot corresponding to the step-down circuit outer core.

[0015] Optionally, the inner core of the step-down circuit includes a ring body, and a plurality of mounting grooves are arranged on the outer wall of the ring body at intervals along the circumferential direction. Adjacent mounting grooves are separated by raised portions. The inner ring of the outer core of the step-down circuit is inserted into the mounting groove body, and the raised portions fill the openings of the winding grooves corresponding to the outer core of the step-down circuit.

[0016] Optionally, the inner core of the step-down circuit includes a filling piece, and the filling piece is filled in the opening of the winding slot corresponding to the outer core of the step-down circuit.

[0017] Furthermore, when the rotor assembly rotates, when the driver inputs d-axis current to the coil winding, the field strength generated by the d-axis current is confined to the buck circuit core, thereby generating magnetic flux in the buck circuit core and inducing a counteracting electromotive force. The counteracting electromotive force is used to offset the reverse electromotive force generated by the main magnetic field generated by the coil winding in the main magnetic field core.

[0018] Therefore, the present invention provides the following effects and / or advantages:

[0019] The step-down circuit core added in this application has a reverse electromotive force suppression capability that is several times improved under the same d-axis current. Therefore, in actual operation, the motor can be operated under a smaller d-axis current, which can effectively suppress the reverse electromotive force and thus increase the speed of the rotating motor.

[0020] Other features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The purposes and other advantages of the application will be realized and attained by the structure particularly pointed out in the description and the appended drawings.

[0021] It is to be understood that both the foregoing general description and the following detailed description of the present application are exemplary and explanatory and are intended to provide further explanation of the application as claimed. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Structure diagram of embodiment one of the present application.

[0023] Figure 2 Structure explosion diagram of embodiment one of the present application.

[0024] Figure 3 Structure cross-sectional view of embodiment one of the present application.

[0025] Figure 4 Structure diagram of the core in the voltage reduction circuit of embodiment one of the present application.

[0026] Figure 5 Structure cross-sectional view of the stator core of embodiment one of the present application.

[0027] Figure 6 Structure diagram of the core magnetic induction line simulation of embodiment one of the present application.

[0028] Figure 7 Structure diagram of the core magnetic induction line simulation without setting the voltage reduction circuit core.

[0029] BRIEF DESCRIPTION OF DRAWINGS

[0030] Housing 1, stator assembly 2, stator core 21, main magnetic field core 211, voltage reduction circuit core 212, voltage reduction circuit outer core 2121, voltage reduction circuit inner core 2122, ring body 21221, mounting groove body 21222, protruding portion 21223, winding groove 214, opening 2141, coil winding 22, rotor assembly 3, rotating shaft 31, permanent magnet 32. DETAILED DESCRIPTION

[0031] For the convenience of understanding of those skilled in the art, the structure of the present application will be further described in detail in combination with the drawings:

[0032] REFERENCE Figure 1-5 A high-speed permanent magnet motor for reducing reverse electromotive force, comprising:

[0033] Shell 1; The shell 1 in this embodiment is only used to fix or support other components. The structure or appearance of the shell 1 in the figure is only exemplary and is not used to limit the shape or structure of the shell 1.

[0034] The stator assembly 2 is arranged inside the housing 1. The stator assembly 2 includes a stator core 21 and a coil winding 22. A rotating shaft 31 channel is formed in the middle of the stator core 21. The stator core 21 is provided with a plurality of winding slots 214 spaced apart along the circumferential direction. The winding slots 214 are arranged to penetrate the stator core 21 in the axial direction. Each winding slot 214 is provided with the coil winding 22. The stator core 21 includes a main magnetic field core 211 and a step-down circuit core 212. The main magnetic field core 211 and the step-down circuit core 212 are magnetically connected. The winding slots 214 corresponding to the main magnetic field core 211 are provided with an opening 2141 at one end toward the axis of the stator core, and the winding slots 214 corresponding to the step-down circuit core 212 are provided with a closed end toward the axis of the stator core.

[0035] The rotor assembly 3 is arranged to penetrate and rotate in the channel of the rotating shaft 31. The rotor assembly 3 includes a rotating shaft 31 and a plurality of permanent magnets 32 that rotate with the rotating shaft 31. The permanent magnets 32 are arranged in the area of ​​the rotating shaft 31 facing the main magnetic field core 211.

[0036] In this embodiment, the coil winding 22 may include three-phase windings (U, V, and W). The operating principle of the coil winding 22 and the permanent magnet 32 ​​in driving the rotation of the rotating shaft 31 is similar to that of conventional rotary motors and will not be elaborated on here. Furthermore, the high-speed permanent magnet motor provided in this embodiment can be used as a rotary mechanism on a machine tool.

[0037] In this embodiment, the coil winding 22 passes through the step-down circuit core 212, and the winding slot 214 corresponding to the step-down circuit core 212 is a closed structure, so that there is no air gap in the inner ring of the step-down circuit core 212, so that a weak magnetic voltage can be obtained at the step-down circuit core 212 as a counteracting electromotive force. During operation, the counteracting electromotive force is offset by the reverse electromotive force generated by the coil winding 22.

[0038] Specifically, the step-down circuit core 212 of this embodiment is disposed at the bottom end of the main magnetic field core 211. The step-down circuit core 212 and the main magnetic field core 211 are arranged in close contact with each other, thereby forming an integrated stator core 21. The winding slots 214 are arranged in an open area 2141 corresponding to the main magnetic field core 211, facilitating magnetic flux coupling. The winding slots 214 are arranged in a closed area corresponding to the step-down circuit core 212, controlling magnetic flux penetration and forming a region of high magnetic resistance and low magnetic leakage in the step-down circuit core 212. Simultaneously, the main magnetic field core 211 and the step-down circuit core 212 are closely attached together, achieving a magnetic connection between the two and jointly forming a composite magnetic circuit.

[0039] This embodiment redesigns the motor's magnetic and electrical circuits, independently considering the d and q axis components of the current. The motor's torque output corresponds to the q axis, so the q axis primarily considers load magnetic circuit optimization, torque ripple optimization, and pole arc coefficient optimization. The motor's field-weakening function corresponds to the d axis, which is primarily responsible for reducing back electromotive force. Therefore, the d axis primarily considers the circuit's ability to generate voltage, specifically its ability to generate inductance, and magnetic circuit saturation. Furthermore, the permanent magnet 32 ​​is aligned with the main magnetic field core 211, ensuring that all magnetic flux in the main magnetic circuit enters the main magnetic field core 211.

[0040] Please see the attached Figure 6 As shown in the figure, the working state of the step-down circuit core 212 is shown. After the step-down circuit core 212 is energized, most of the magnetic flux lines in the step-down circuit core 212 surround themselves and are independent of the main magnetic field at the main magnetic field core 211. The step-down circuit core 212 operates independently. Figure 7 The magnetic flux lines simulation diagram shows that although some leakage flux from the step-down circuit core 212 penetrates the axis, the area corresponding to the axis is free of permanent magnets 32, thus having no effect on the motor's torque output. Due to the presence of the step-down circuit core 212, when the driver inputs d-axis current to the motor, the field strength generated by the d-axis current is largely limited by the step-down circuit core 212 and cannot be fully transmitted to the permanent magnets 32. Therefore, the permanent magnets 32 cannot be truly demagnetized. However, the voltage generated by the d-axis current remains and does not disappear due to the magnetic field not penetrating the permanent magnets 32. On the contrary, because the winding slots 214 corresponding to the step-down circuit core 212 are closed and have no air gap, and the step-down circuit core 212 is sufficiently deep, the generated inductance is greatly increased, which in turn generates a larger magnetic flux, thereby significantly increasing the voltage induced by the d-axis current on the step-down circuit core 212. From the driver's perspective, this strengthens the motor's magnetic field weakening capability.

[0041] Compared to a solution without the step-down circuit core 212, the added step-down circuit core 212 offers several times greater back electromotive force suppression capability at the same d-axis current. Therefore, in actual operation, the motor can operate at a lower d-axis current. Furthermore, the d and q axes effectively share a common circuit, and the higher inductance suppresses high-frequency currents, filtering out high-frequency eddy currents and reducing motor iron losses.

[0042] Furthermore, the main magnetic field core 211 and the step-down circuit core 212 are both composed of a plurality of stacked steel plates, and the main magnetic field core 211 and the step-down circuit core 212 are arranged in contact with each other.

[0043] Furthermore, the thickness ratio of the main magnetic field core 211 to the step-down circuit core 212 is 6:0.5-2.

[0044] In this embodiment, the thickness ratio of the main magnetic field core 211 to the step-down circuit outer core 2121 is 6:1. Other ratios within this range are possible in other embodiments. This thickness ratio can control the generation of magnetic flux by the step-down circuit core 212 and induce a voltage that offsets the electromotive force, effectively shunting the magnetic flux without significantly reducing the energy output of the main magnetic circuit.

[0045] Furthermore, the step-down circuit core 212 includes a step-down circuit outer core 2121 and a step-down circuit inner core 2122. The cross-section of the step-down circuit outer core 2121 is the same as the cross-section of the main magnetic field core 211. The step-down circuit inner core 2122 closes the opening 2141 of the winding slot 214 corresponding to the step-down circuit outer core 2121.

[0046] In this embodiment, by making the steel plate of the outer iron core 2121 of the step-down circuit have the same structure as the steel plate of the main magnetic field iron core 211, it is possible to directly stack the corresponding total number of steel plates when preparing the stator iron core 21, and then wind the corresponding coil winding 22 at the winding groove 214. Finally, the inner iron core 2122 of the step-down circuit is installed to the bottom end of the stator iron core 21 so that the winding groove 214 at the bottom end of the stator iron core 21 is closed. It can have the characteristics of simple structure and easy assembly, which can reduce production costs and share the existing punching sheets and heat dissipation structure of the motor.

[0047] Optionally, the inner core 2122 of the step-down circuit includes a ring body 21221, and the outer wall of the ring body 21221 is provided with a plurality of mounting grooves 21222 at intervals along the circumferential direction, and adjacent mounting grooves 21222 are separated by protrusions 21223. The inner ring of the outer core 2121 of the step-down circuit is inserted into the mounting groove 21222, and the protrusion 21223 is filled in the opening 2141 of the winding groove 214 corresponding to the outer core 2121 of the step-down circuit.

[0048] In this embodiment, reference Figure 4 The outer wall of the ring body 21221 is provided with a plurality of mounting grooves 21222 at intervals along the circumferential direction. The mounting grooves 21222 cooperate with the structure of the inner ring surface of the inner iron core 2122 of the step-down circuit, so that the inner ring surface of the inner iron core 2122 of the step-down circuit can be inserted into the mounting grooves 21222, and the protrusions 21223 are filled in the openings 2141 of the winding grooves 214 corresponding to the outer iron core 2121 of the step-down circuit, thereby closing the corresponding openings 2141 of the winding grooves 214 and eliminating the air gaps of the corresponding winding grooves 214.

[0049] Furthermore, when the rotor assembly 3 rotates, when the driver inputs d-axis current to the coil winding 22, the field strength generated by the d-axis current is confined to the buck circuit core 212, thereby generating magnetic flux in the buck circuit core 212 and inducing a counteracting electromotive force, which is used to offset the reverse electromotive force generated by the core main magnetic field generated by the coil winding 22 in the main magnetic field core 211.

[0050] Example 2

[0051] This embodiment is basically the same as the first embodiment, except that:

[0052] The structure of the step-down circuit inner core 2122 is different. The step-down circuit inner core 2122 includes a filling piece, and the filling piece is filled in the opening 2141 of the winding slot 214 corresponding to the step-down circuit outer core 2121.

[0053] In this embodiment, the ring body 21221 is not provided. Instead, the opening 2141 of the winding slot 214 is directly filled with a filler, thereby closing the corresponding opening 2141 of the winding slot 214. This can reduce the weight of the iron core 2122 in the step-down circuit and has a simpler structure.

[0054] It should be noted that in the claims, any reference signs placed between parentheses shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claim. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, third etc. does not indicate any order. These words may be interpreted as names.

[0055] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0056] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0057] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

Claims

1. A high-speed permanent magnet motor with reduced back electromotive force, characterized in that: include: case; A stator assembly is disposed inside the housing, the stator assembly comprising a stator core and coil windings, a rotating shaft channel is formed in the middle of the stator core, the stator core is provided with a plurality of winding slots spaced apart along the circumferential direction, the winding slots are arranged to penetrate the stator core in the axial direction, each of the winding slots is provided with the coil winding, the stator core comprises a main magnetic field core and a step-down circuit core, the main magnetic field core and the step-down circuit core are magnetically connected, the winding slots corresponding to the main magnetic field core are open at one end facing the axis of the stator core, and the winding slots corresponding to the step-down circuit core are closed at one end facing the axis of the stator core; a rotor assembly, penetrating and rotatably disposed in the shaft channel, the rotor assembly comprising a shaft and a plurality of permanent magnets that rotate along with the shaft, the permanent magnets being disposed in a region of the shaft directly opposite the main magnetic field core; The main magnetic field core and the step-down circuit core are both composed of a plurality of stacked steel plates, and the main magnetic field core and the step-down circuit core are arranged in contact with each other; The step-down circuit core includes a step-down circuit outer core and a step-down circuit inner core. The cross-section of the step-down circuit outer core is the same as the cross-section of the main magnetic field core. The step-down circuit inner core closes the opening of the winding slot corresponding to the step-down circuit outer core.

2. A high-speed permanent magnet motor with reduced back electromotive force according to claim 1, characterized in that: The thickness ratio of the main magnetic field core to the step-down circuit core is 6:0.5-2.

3. The high-speed permanent magnet motor with reduced back electromotive force according to claim 1, characterized in that: The inner iron core of the step-down circuit includes a ring body, and the outer wall of the ring body is provided with a plurality of mounting grooves spaced circumferentially, and adjacent mounting grooves are separated by raised portions. The inner ring of the outer iron core of the step-down circuit is inserted into the mounting groove body, and the raised portions fill the openings of the winding grooves corresponding to the outer iron core of the step-down circuit.

4. The high-speed permanent magnet motor with reduced back electromotive force according to claim 1, characterized in that: The inner iron core of the step-down circuit includes a filling piece, and the filling piece is filled in the opening of the winding slot corresponding to the outer iron core of the step-down circuit.

5. The high-speed permanent magnet motor with reduced back electromotive force according to claim 1, characterized in that: When the rotor assembly rotates, when the driver inputs a d-axis current to the coil winding, the field strength generated by the d-axis current is confined to the buck circuit core, thereby generating a magnetic flux in the buck circuit core and inducing a counteracting electromotive force. The counteracting electromotive force is used to offset the reverse electromotive force generated by the main magnetic field generated by the coil winding in the main magnetic field core.

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