A method for determining the maximum operating current of a pseudo-direct-drive magnetic gear composite motor

Abstract

This invention discloses a method for determining the maximum operating current of a pseudo-direct-drive magnetic gear composite motor, belonging to the field of motors. This method enables the determination of the maximum operating current of the pseudo-direct-drive magnetic gear composite motor, resolving the contradiction between torque amplification in the magnetic gear section and the limitation on maximum safe transmission torque. It can fully leverage the advantages of the magnetic gear composite motor, improve the motor's torque density, and push the motor's performance limits, providing a reference for engineering applications and facilitating the widespread industrial application of magnetic gear composite motors. Furthermore, this method, in addition to considering motor step loss, further considers the impact of motor heat dissipation on its maximum current density. While maximizing the motor's output torque under the maximum safe transmission torque limit, it further ensures the stability of motor operation, resulting in optimal torque performance.

Description

Technical Field

[0001] This invention belongs to the field of electric motors, and more specifically, relates to a method for determining the maximum operating current of a pseudo-direct drive magnetic gear composite motor. Background Technology

[0002] In recent years, magnetic gear composite motors have become a focus of research both domestically and internationally. Especially in low-speed, high-torque applications, magnetic gear composite motors do not suffer from problems such as wear, vibration, noise, and regular maintenance caused by mechanical contact. They also have many advantages such as high torque density, high power factor, and low current density.

[0003] Unlike conventional motors, magnetic gear composite motors have a magnetic gear section that amplifies torque. However, the magnetic gear section also has a maximum safe transmission torque, which limits the motor's torque. Therefore, the maximum torque and the maximum allowable operating current of the motor are still unclear. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a method for determining the maximum operating current of a pseudo-direct drive magnetic gear composite motor, thereby solving the technical problem that the motor performance cannot be optimized because the maximum operating current of the motor cannot be determined.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a method for determining the maximum operating current of a pseudo-direct-drive magnetic gear composite motor is provided, comprising:

[0006] Determine whether the output torque of the motor at the maximum current density is greater than the maximum safe transmission torque;

[0007] If so, then set the current working angle of the motor's magnetic gear to the working angle of the magnetic gear corresponding to the maximum safe transmission torque, and adjust the amplitude and phase of the motor's working current so that the torque of the motor's internal permanent magnet rotor is zero. The working current under this condition is the maximum working current.

[0008] If not, the amplitude of the current operating current of the motor remains unchanged, the phase angle of the current operating current is adjusted to maximize the output torque of the motor, and the position of the modulation ring rotor of the motor is adjusted while the position of the inner permanent magnet rotor remains unchanged, so that the resultant torque of the inner permanent magnet rotor is zero. The operating current under this condition is the maximum operating current.

[0009] According to a second aspect of the present invention, an electronic device is provided, comprising: a computer-readable storage medium and a processor;

[0010] The computer-readable storage medium is used to store executable instructions;

[0011] The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in the first aspect.

[0012] According to a third aspect of the invention, a computer-readable storage medium is provided, the computer-readable storage medium storing computer instructions for causing a processor to perform the method as described in the first aspect.

[0013] According to a fourth aspect of the invention, a computer program product is provided, comprising a computer program or instructions that, when executed by a processor, implement the method described in the first aspect.

[0014] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0015] 1. The method for determining the maximum operating current of the pseudo-direct drive magnetic gear composite motor provided by this invention enables the maximum operating current of the pseudo-direct drive magnetic gear composite motor to be determined, which solves the contradiction between the torque amplification of the magnetic gear part and the limitation of the maximum safe transmission torque. It can give full play to the advantages of the magnetic gear composite motor, improve the torque density of the motor, and push the performance limit of the motor. It provides a reference for engineering applications and is conducive to the promotion and application of magnetic gear composite motors in industry.

[0016] 2. The method provided by this invention, in addition to considering the motor's step loss, further considers the impact of motor heat dissipation on its maximum current density. While maximizing the motor's output torque under the maximum safe transmission torque limit, it further ensures the stability of motor operation and optimizes the motor's torque performance. Attached Figure Description

[0017] Figure 1 A schematic diagram of the structure of an existing pseudo-direct drive magnetic gear composite motor;

[0018] Figure 2 (a) and (b) are schematic diagrams of the pseudo-direct drive magnetic gear composite motor after removing the inner rotor permanent magnet and the stator side permanent magnet, respectively.

[0019] Figure 3 A schematic diagram of the power flow of a pseudo-direct-drive magnetic gear composite motor;

[0020] Figure 4 A schematic diagram of the flux linkage vector of a pseudo-direct-drive magnetic gear composite motor;

[0021] Figure 5 A schematic flowchart illustrating the method for determining the maximum operating current of a pseudo-direct-drive magnetic gear composite motor provided in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Because the magnetic gear component has a maximum safe transmission torque, which is the product of the maximum transmission torque of the magnetic gear and a safety factor, the electromagnetic torque of the magnetic gear composite motor, after being amplified by the magnetic gear, needs to be less than the maximum safe transmission torque of the magnetic gear, thus limiting the electromagnetic torque and maximum operating current of the motor.

[0024] Based on this, embodiments of the present invention provide a method for determining the maximum operating current of a pseudo-direct-drive magnetic gear composite motor, including:

[0025] Determine whether the output torque of the motor at the maximum current density is greater than the maximum safe transmission torque;

[0026] If so, then set the current working angle of the motor's magnetic gear to the working angle of the magnetic gear corresponding to the maximum safe transmission torque, and adjust the amplitude and phase of the motor's working current so that the torque of the motor's internal permanent magnet rotor is zero. The working current under this condition is the maximum working current.

[0027] If not, keep the amplitude of the current operating current of the motor constant, adjust the phase angle of the current operating current to maximize the output torque of the motor, and adjust the position of the modulation ring rotor of the motor while keeping the position of the inner permanent magnet rotor constant so that the resultant torque of the inner permanent magnet rotor is zero. The operating current under this condition is the maximum operating current.

[0028] The output torque of the motor is the torque of the modulation ring rotor.

[0029] like Figure 1 As shown, a traditional pseudo-direct-drive magnetic gear composite motor, radially from the outside to the inside, includes: an outer stator, a modulation ring rotor 2, and an inner permanent magnet rotor 3; both the stator and rotor are cylindrical; the outer stator core 1 has a semi-open slot, into which the stator winding is placed, and the permanent magnet is attached to the inner surface of the stator core; the modulation ring rotor 2 consists of multiple modulation blocks, typically connected by a connecting bridge; the inner permanent magnet rotor 3 includes a rotor core and permanent magnets attached to the surface of the rotor core. Figure 1 Taking the pseudo-direct-drive magnetic gear composite motor shown as an example, the number of pole pairs of the internal permanent magnet rotor is P. i =2, Modulation ring pole pair number Z m =23, Number of pole pairs P of permanent magnets on the stator sides =21, number of stator slots Z s =6, the number of pole pairs of the stator armature winding is P a =2.

[0030] Based on the characteristics of magnetic gears, it can be seen that the internal permanent magnet rotor is a high-speed rotor, while the modulation ring rotor is a low-speed rotor, i.e., the output rotor. In other words, the torque of the modulation ring rotor is the output torque.

[0031] When the stator-side permanent magnets are removed, the number of pole pairs in the high-speed rotor and armature windings are equal, and they can be considered to together constitute a conventional surface-mounted permanent magnet synchronous motor. The number of pole pairs in the modulation ring, Z... m Number of permanent magnet pole pairs P on the stator side s and the number of pole pairs P of the internal permanent magnet rotor i Equation (1) is satisfied. As a magnetic gear composite motor, the speed ratio of the high-speed rotor to the low-speed rotor satisfies Equation (2).

[0032] Z m =P s +P i (1)

[0033]

[0034] Among them, G r For speed ratio, Ω i For high-speed rotor speed, Ω m This is the low-speed rotor speed.

[0035] The pseudo-direct-drive magnetic gear composite motor is analyzed in two parts. One part involves removing the permanent magnets from the inner rotor, such as... Figure 2 As shown in (a), this structure is similar to a flux-reversing motor. No torque is generated in the inner rotor, but electromagnetic torque is generated in the modulated ring rotor due to the combined action of the armature windings and the stator-side permanent magnets. Another part involves removing the stator-side permanent magnets, such as... Figure 2 As shown in (b), this structure is similar to a conventional surface-mounted permanent magnet motor. The number of pole pairs of the permanent magnets in the inner rotor is equal to the number of pole pairs of the armature winding, which will generate torque on the inner rotor, while the outer rotor (i.e., the modulation ring rotor) has no torque.

[0036] The stator-side permanent magnets, the inner permanent magnet rotor, and the modulation ring rotor together form the magnetic gear section. The magnetic gear is responsible for transmitting power, transferring torque from the high-speed rotor to the low-speed rotor according to the speed ratio. In low-speed applications, the outer rotor is often connected to the mechanical load, while the inner permanent magnet rotor idles. The pseudo-direct-drive magnetic gear composite motor has a dual-rotor structure, and its power flow is as follows: Figure 3 As shown. The input current passes through the surface-mounted permanent magnet motor and the flux-reversing motor on the inner and outer rotors, respectively, to generate electromagnetic torques, T, respectively. SPM T FRM Because the inner rotor is idling, the resultant torque T on the inner rotor is...in The value is 0, which is determined by the torque T of the magnetic gear section on the inner rotor. MGi Torque T of surface-mounted permanent magnet motor SPM The combined effect is shown in equation (3). The internal rotor torque T of the magnetic gear section... MGi External rotor torque T MGo The ratio is shown in equation (4). In addition, the torque transmitted by the magnetic gear, the torque of the magnetic flux reverse motor section, and the torque generated by magnetic coupling together determine the output torque of the modulation ring rotor.

[0037] T in =T MGi +T SPM =0 (3)

[0038]

[0039] In pseudo-direct-drive magnetic gear composite motors, the magnetic circuits of the conventional permanent magnet motor section and the magnetic gear section are coupled, rather than simply superimposed with the torques of each part. The magnetic flux linkage vector diagram of the motor is shown below. Figure 4 As shown, the flux linkage of the stator winding is Ψ. a The flux linkage of the permanent magnet on the stator side is Ψ s The flux linkage of the inner rotor permanent magnet is Ψ i The modulated magnetic flux linkage is Ψ mi Ψ mi With Ψ s The included angle is δ. When δ = 90°, the torque of the magnetic gear section is at its maximum, and this torque is the loss-of-step torque. To ensure that the magnetic gear section does not lose steps, δ is generally < 90°. mi q-axis and Ψ a The included angle is β, which is called the current angle. β is equal to the phase angle of the operating current. When β = 0, the conventional permanent magnet motor part is i. d =0.

[0040] As can be seen from the magnetic flux vector diagram of the motor, the output torque of the pseudo-direct drive magnetic gear composite motor can be expressed as Equation (5).

[0041] T o =p(Ψ) mi +Ψ a )×Ψ s (5)

[0042] According to the flux linkage vector diagram and torque formula (5), due to the presence of magnetic coupling, the output torque of the motor is related not only to the power angle of the magnetic gear section but also to the current angle of the conventional permanent magnet motor section. As the current angle β increases, the output torque exhibits a characteristic of first increasing and then decreasing; for example... Figure 4 As shown, when the current angle β increases to Ψ mi With Ψ aWhen the two sides coincide, the output torque is the maximum. However, in reality, due to material saturation, the point of maximum torque is uncertain. But what is certain is that within a specific angle range, the output torque of the motor increases with the increase of β.

[0043] The method for determining the maximum operating current of a pseudo-direct-drive magnetic gear composite motor provided in this invention considers that, to prevent motor step loss, the magnetic gear portion of the magnetic gear composite motor has a maximum safe transmission torque, which corresponds to a magnetic gear operating angle. Therefore, the method first determines whether the motor's output torque at the maximum current density is greater than the maximum safe transmission torque.

[0044] (1) If the output torque under the maximum current density is greater than the maximum safe transmission torque, then the working angle of the magnetic gear is fixed to ensure that the magnetic gear is under the maximum safe transmission torque (i.e., the current working angle of the magnetic gear is the working angle of the magnetic gear corresponding to the maximum safe transmission torque), so as to maximize the output torque of the motor; the amplitude and phase of the motor current are adjusted so that the combined torque of the high-speed rotor is 0, so as to ensure that the motor is in a stable working state. The working current under this condition is the maximum working current, and correspondingly, the current density under this condition is the maximum working current density. It can be understood that when the high-speed rotor is fixed, the angle between the positions of the low-speed rotor and the high-speed rotor multiplied by the number of pole pairs of the low-speed rotor is the working angle of the magnetic gear.

[0045] (2) If the output torque under the maximum current density is less than the maximum safe transmission torque, then the magnitude of the fixed working current remains unchanged, and the current angle β is adjusted to change the phase of the working current. Find the current angle that maximizes the overall output torque T0 of the motor, so that the torque of the modulated ring rotor (i.e. the overall output torque of the motor) is maximized under the condition of meeting the heat dissipation requirements. Fix the position of the high-speed rotor and change the position of the low-speed rotor to change the working angle of the magnetic gear. Find the working angle of the magnetic gear that makes the combined torque of the high-speed rotor zero, so as to ensure that the motor is in a stable working state. The working current under this condition is the maximum working current, and correspondingly, the electrical density under this condition is the maximum working electrical density.

[0046] It is understandable that the combined torque of the high-speed rotor will change every time the current angle is adjusted. Therefore, it is necessary to adjust the position of the low-speed rotor to keep the torque of the high-speed rotor at 0, so as to ensure that the motor is in a stable working state.

[0047] Considering that the maximum allowable current density of a motor is related not only to its power rating but also to its cooling method, in order to further improve the reliability of this method, preferably, the maximum current density is the maximum allowable current density of the motor under the condition of meeting heat dissipation requirements.

[0048] In other words, the maximum current density is the maximum allowable current density of the motor under the heat dissipation requirements, determined based on the power rating of the magnetic gear composite motor and the cooling method used. When determining the maximum allowable current density of the motor, the power rating of the motor and the cooling method used should be considered. Motors with higher power ratings have the highest allowable maximum current density; motors using water cooling have a higher allowable maximum current density than those using natural cooling. The maximum allowable current density of the motor under the aforementioned heat dissipation requirements can be initially determined by professionals based on practical experience, and then finally determined through actual simulation and thermal analysis.

[0049] The embodiments of the present invention can determine the maximum operating current of the magnetic gear composite motor, and solve the contradiction that there is a maximum safe transmission torque limit while the magnetic gear part amplifies the torque. It can give full play to the advantages of the magnetic gear composite motor and is conducive to the promotion and application of the magnetic gear composite motor in industry.

[0050] This invention provides an electronic device, including: a computer-readable storage medium and a processor;

[0051] The computer-readable storage medium is used to store executable instructions;

[0052] The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in any of the above embodiments.

[0053] This invention provides a computer-readable storage medium storing computer instructions that cause a processor to perform the method described in any of the above embodiments.

[0054] This invention provides a computer program product, including a computer program or instructions, which, when executed by a processor, implement the method described in any of the above embodiments.

[0055] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the maximum operating current of a pseudo-direct-drive magnetic gear composite motor, characterized in that, include: Determine whether the output torque of the motor at the maximum current density is greater than the maximum safe transmission torque; If so, then set the current working angle of the motor's magnetic gear to the working angle of the magnetic gear corresponding to the maximum safe transmission torque, and adjust the amplitude and phase of the motor's working current so that the torque of the motor's internal permanent magnet rotor is zero. The working current under this condition is the maximum working current. If not, the amplitude of the current operating current of the motor remains unchanged, the phase angle of the current operating current is adjusted to maximize the output torque of the motor, and the position of the modulation ring rotor of the motor is adjusted while the position of the inner permanent magnet rotor remains unchanged, so that the resultant torque of the inner permanent magnet rotor is zero. The operating current under this condition is the maximum operating current.

2. The method as described in claim 1, characterized in that, The maximum current density is the maximum current density allowed by the motor when the heat dissipation requirements are met.

3. The method as described in claim 1, characterized in that, The phase angle of the motor operating current and Ψ mi q-axis components and Ψ a The included angles are equal; where Ψ a Ψ is the flux linkage of the stator winding. mi It is the magnetic flux linkage of the internal rotor permanent magnet after modulation.

4. The method as described in claim 3, characterized in that, The output torque T of the motor o =p(Ψ) mi +Ψ a )×Ψ s Where Ψs is the flux linkage of the stator-side permanent magnet, and p is the torque coefficient.

5. An electronic device, characterized in that, include: Computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in any one of claims 1-4.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a processor to perform the method as described in any one of claims 1-4.

7. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by a processor, they implement the method as described in any one of claims 1 to 4.

Images