Method for determining maximum working current of pseudo direct drive type magnetic gear composite motor

Abstract

The invention discloses a method for determining the maximum working current of a pseudo-direct-drive magnetic gear composite motor, which belongs to the field of motors, enables the maximum working current of the pseudo-direct-drive magnetic gear composite motor to be determined, solves the contradiction that the maximum safe transmission torque is limited while the torque of a magnetic gear part is amplified, and improves the reliability of the motor. The advantages of the magnetic gear composite motor can be fully exerted, the torque density of the motor is improved, the performance of the motor is limited, reference is provided for engineering application, and industrial application and popularization of the magnetic gear composite motor are facilitated; besides, the method further considers the influence of heat dissipation of the motor on the maximum current density on the basis of considering out-of-step of the motor, and further ensures the operation stability of the motor and enables the torque performance of the motor to be optimal while maximizing the output torque of the motor under the limit of the maximum safe transmission torque.

Description

Technical Field

[0001] The present invention belongs to the field of motors, and more specifically, relates to a method for determining a maximum operating current of a pseudo direct-drive magnetic gear compound motor. Background Art

[0002] In recent years, magnetic gear compound motors have become the focus of research at home and abroad, especially in low-speed and high-torque situations. Magnetic gear compound motors do not have 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, the magnetic gear compound motor has a magnetic gear part that plays the role of torque amplification. However, the magnetic gear part also has a maximum safe transmission torque, which in turn limits the torque of the motor. Therefore, the maximum torque and maximum allowable operating current of the motor are still unclear. Summary of the invention

[0004] In view of the above 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 compound motor, thereby solving the technical problem that the motor performance cannot be optimized due to the inability to determine the maximum operating current of the motor.

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

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

[0007] If yes, the current working angle of the magnetic gear of the motor is set to the working angle of the magnetic gear corresponding to the maximum safe transmission torque, and the amplitude and phase of the working current of the motor are adjusted so that the torque of the inner permanent magnet rotor of the motor is zero. The working current under this working condition is the maximum working current;

[0008] If not, the amplitude of the current working current of the motor is kept unchanged, and the phase angle of the current working current is adjusted to maximize the output torque of the motor. While the position of the inner permanent magnet rotor of the motor remains unchanged, the position of the modulation ring rotor of the motor is adjusted to make the synthetic torque of the inner permanent magnet rotor zero. The working current under this working condition is the maximum working current.

[0009] According to a second aspect of the present invention, there is provided an electronic device, 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 used to read the 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 present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to cause a processor to execute the method as described in the first aspect.

[0013] According to a fourth aspect of the present invention, there is provided a computer program product, comprising a computer program or instructions, wherein when the computer program or instructions are executed by a processor, the method according to the first aspect is implemented.

[0014] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0015] 1. The method for determining the maximum operating current of a pseudo direct-drive magnetic gear compound motor provided by the present invention enables the maximum operating current of the pseudo direct-drive magnetic gear compound motor to be determined, thereby resolving the contradiction that the maximum safe transmission torque is limited while the torque of the magnetic gear part is amplified. The method can give full play to the advantages of the magnetic gear compound motor, improve the torque density of the motor, and maximize the performance limit of the motor, providing a reference for engineering applications, which is beneficial to the promotion and application of magnetic gear compound motors in industry.

[0016] 2. The method provided by the present invention not only takes into account the motor out of step, but also further considers the influence of the motor heat dissipation on its maximum current density. While maximizing the motor output torque under the maximum safe transmission torque limit, it further ensures the stability of the motor operation and optimizes the torque performance of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of an existing pseudo direct drive magnetic gear compound motor;

[0018] Figure 2 (a) and (b) are schematic diagrams of the structure of the pseudo direct drive magnetic gear compound motor with the inner rotor permanent magnet and the stator side permanent magnet removed respectively;

[0019] Figure 3 It is a schematic diagram of the power flow of the pseudo direct drive magnetic gear compound motor;

[0020] Figure 4 It is a schematic diagram of the flux vector of the pseudo direct drive magnetic gear compound motor;

[0021] Figure 5 A schematic flow chart of a method for determining the maximum operating current of a pseudo direct-drive magnetic gear compound motor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Since the magnetic gear part has a maximum safe transfer torque, which is the product of the maximum transfer torque of the magnetic gear and the safety factor, the electromagnetic torque of the magnetic gear composite motor needs to be smaller than the maximum safe transfer torque of the magnetic gear after being amplified by the magnetic gear, thereby limiting the electromagnetic torque and maximum working current of the motor.

[0024] Based on this, an embodiment of the present invention provides a method for determining the maximum operating current of a pseudo direct drive magnetic gear compound motor, comprising:

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

[0026] If yes, the current working angle of the magnetic gear of the motor is set to the working angle of the magnetic gear corresponding to the maximum safe transmission torque, and the amplitude and phase of the working current of the motor are adjusted so that the torque of the inner permanent magnet rotor of the motor is zero. The working current under this working condition is the maximum working current;

[0027] If not, the amplitude of the current working current of the motor is kept constant, the phase angle of the current working 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 of the motor remains unchanged so that the synthetic torque of the inner permanent magnet rotor is zero. The working current under this working condition is the maximum working current;

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

[0029] like Figure 1 As shown, the conventional pseudo direct drive type magnetic gear compound motor includes radially from outside to inside: an outer stator, a modulation ring rotor 2 and an inner permanent magnet rotor 3; both the stator and the rotor are cylindrical; the outer stator core 1 is provided with a semi-open slot, in 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 is composed of a plurality of modulation blocks, which are generally connected by a connecting bridge; the inner permanent magnet rotor 3 includes a rotor core and a permanent magnet attached to the upper side of the rotor core. Figure 1 As an example, the pseudo direct drive magnetic gear compound motor shown in the figure has an inner permanent magnet rotor pole pair number of P i =2, modulation ring pole number Z m =23, number of permanent magnet pole pairs on the stator side Ps =21, number of stator slots Z s =6, the number of pole pairs of the stator armature winding is P a =2.

[0030] From the characteristics of the magnetic gear, it can be seen that the inner permanent magnet rotor is a high-speed rotor, and the modulation ring rotor is a low-speed rotor, namely the output rotor, that is, the torque of the modulation ring rotor is the output torque.

[0031] When the permanent magnets on the stator side are removed, the number of pole pairs of the high-speed rotor and armature windings is equal, and it can be considered that the two together constitute a conventional surface-mounted permanent magnet synchronous motor. m , Number of permanent magnet pole pairs on the stator side P s and the number of inner permanent magnet rotor pole pairs P i Satisfies equation (1). As a magnetic gear compound 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 is the speed ratio, Ω i is the high speed rotor speed, Ω m is the low rotor speed.

[0035] The pseudo direct drive magnetic gear compound motor is divided into two parts for analysis. One part is to remove the inner rotor permanent magnet, such as Figure 2 As shown in (a) in the figure, this structure is similar to a flux reversal motor. No torque is generated in the inner rotor, and the modulation ring rotor generates electromagnetic torque under the combined action of the armature winding and the stator side permanent magnet. The other part is to remove the stator side permanent magnet, 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 inner rotor permanent magnet 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 magnet, the inner permanent magnet rotor and the modulation ring rotor together form the magnetic gear part. The magnetic gear is responsible for transmitting power and 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 and the inner permanent magnet rotor is idling. The pseudo direct drive magnetic gear compound motor is a dual-rotor structure, and its power flow is as follows: Figure 3 The input current passes through the surface-mounted permanent magnet motor and the flux reversal motor on the inner and outer rotors to generate electromagnetic torque, which are T SPM 、T FRM , since the inner rotor is idling, the resultant torque T on the inner rotor isin is 0, which is the torque T of the magnetic gear part on the inner rotor MGi And the surface mounted permanent magnet motor partial torque T SPM The inner rotor torque T of the magnetic gear part MGi , outer rotor torque T MGo The ratio relationship is as shown in formula (4). In addition, the torque transmitted by the magnetic gear, the torque of the flux reversal motor part and the torque generated by magnetic coupling jointly determine the output torque of the modulation ring rotor.

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

[0038]

[0039] In the pseudo direct drive magnetic gear compound motor, the magnetic circuits of the conventional permanent magnet motor part and the magnetic gear part are coupled, and the torques of each part are not simply superimposed. The magnetic flux vector diagram of the motor is as follows Figure 4 As shown, the magnetic flux 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 flux linkage after modulation is Ψ mi ,Ψ mi With s The angle is δ. When δ=90°, the torque of the magnetic gear part is the maximum, which is the step-out torque. In order to ensure that the magnetic gear part does not step out, generally δ<90°. mi The q-axis and Ψ a The angle between them is β, which is called the current angle. β is equal to the phase angle of the working current. When β = 0, the conventional permanent magnet motor part is i d =0.

[0040] From the flux vector diagram of the motor, it can be seen that the output torque of the pseudo direct drive magnetic gear compound motor can be expressed as formula (5).

[0041] T o = p(Ψ mi +Ψ a )×Ψ s (5)

[0042] According to the flux vector diagram and torque formula (5), due to the existence of magnetic coupling, the output torque of the motor is not only related to the power angle of the magnetic gear part, but also to the current angle of the conventional permanent magnet motor part. As the current angle β increases, the output torque increases first and then decreases; Figure 4 As shown, when the current angle β increases to Ψ mi With aWhen they overlap, the output torque is maximum. However, in actual situations, due to the saturation of the material, the maximum torque point is uncertain. However, it is certain that within a specific angle range, as β increases, the output torque of the motor increases.

[0043] The method for determining the maximum operating current of a pseudo direct-drive magnetic gear compound motor provided by an embodiment of the present invention takes into account that in order to prevent the motor from losing step, the magnetic gear part of the magnetic gear compound motor has a maximum safe transmission torque, and the maximum safe transmission torque corresponds to a magnetic gear working angle. Therefore, first determine whether the output torque of the motor 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 transfer torque, the working angle of the magnetic gear is fixed to ensure that the magnetic gear is under the maximum safe transfer torque (that is, the current working angle of the magnetic gear is the working angle of the magnetic gear corresponding to the maximum safe transfer torque) to maximize the output torque of the motor; adjust the amplitude and phase of the motor current so that the synthetic torque of the high-speed rotor is 0 to ensure that the motor is in a stable working state. The working current under this working condition is the maximum working current, and accordingly, the current density under this working condition is the maximum working current density. It can be understood that when the high-speed rotor is fixed, the position angle between 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 at the maximum current density is less than the maximum safe transmission torque, the amplitude of the fixed working current remains unchanged, and the current angle β is adjusted to change the phase of the working current to find the current angle that maximizes the overall output torque T0 of the motor, so as to maximize the torque of the modulation ring rotor (i.e., the overall output torque of the motor) while meeting the heat dissipation requirements; the high-speed rotor position is fixed, the low-speed rotor position is changed, thereby changing the working angle of the magnetic gear, and finding the working angle of the magnetic gear that makes the synthetic torque of the high-speed rotor 0, so as to ensure that the motor is in a stable working state. The working current under this working condition is the maximum working current, and accordingly, the current density under this working condition is the maximum working current density.

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

[0047] Taking into account that the maximum current density allowed by the motor is related not only to its power level but also to the cooling method adopted by it, in order to further improve the reliability of the present method, preferably, the maximum current density is the maximum current density allowed by the motor while meeting the heat dissipation requirements.

[0048] That is, the maximum current density is the maximum current density allowed by the motor under the heat dissipation requirements determined according to the power level of the magnetic gear compound motor and the cooling method adopted. The power level of the motor and the cooling method adopted should be considered when confirming the maximum current density allowed by the motor. The larger the power of the motor, the greater its maximum allowable current density; the maximum allowable current density of the motor using water cooling is greater than that of the motor using natural cooling. The maximum current density allowed by the motor under the heat dissipation requirements mentioned above can be preliminarily determined by professionals based on actual experience, and then finally determined by actual simulation, thermal analysis and other methods.

[0049] The embodiment of the present invention can determine the maximum operating current of the magnetic gear compound motor, solves the contradiction that the maximum safe transmission torque is limited while the magnetic gear partial torque is amplified, can give full play to the advantages of the magnetic gear compound motor, and is conducive to the promotion and application of the magnetic gear compound motor in industry.

[0050] An embodiment of the present 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 used to read the executable instructions stored in the computer-readable storage medium and execute the method described in any of the above embodiments.

[0053] An embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to execute the method described in any of the above embodiments.

[0054] An embodiment of the present invention provides a computer program product, including a computer program or instructions, and when the computer program or instructions are executed by a processor, the method described in any of the above embodiments is implemented.

[0055] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope of the present invention.

Claims

1. A method for determining the maximum operating current of a pseudo direct drive magnetic gear compound motor, characterized in that: include: Determining whether the output torque of the motor at the maximum current density is greater than the maximum safe transmission torque; If yes, the current working angle of the magnetic gear of the motor is set to the working angle of the magnetic gear corresponding to the maximum safe transmission torque, and the amplitude and phase of the working current of the motor are adjusted so that the torque of the inner permanent magnet rotor of the motor is zero. The working current under this working condition is the maximum working current; If not, the amplitude of the current working current of the motor is kept unchanged, and the phase angle of the current working current is adjusted to maximize the output torque of the motor. While the position of the inner permanent magnet rotor of the motor remains unchanged, the position of the modulation ring rotor of the motor is adjusted to make the synthetic torque of the inner permanent magnet rotor zero. The working current under this working condition is the maximum working current.

2. The method according to claim 1, characterized in that The maximum current density is the maximum current density allowed by the motor when the heat dissipation requirement is met.

3. The method according to claim 1, characterized in that The phase angle of the motor operating current and Ψ mi The q-axis component of a The angles of a is the flux linkage of the stator winding, Ψ mi It is the magnetic flux of the inner rotor permanent magnet after modulation.

4. The method according to claim 3, characterized in that The output torque T of the motor o = p(Ψ mi +Ψ a )×Ψ s ; Wherein, Ψs is the magnetic flux of the permanent magnet on the stator side, and p is the torque coefficient.

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

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to execute the method according to any one of claims 1 to 4.

7. A computer program product comprising a computer program or instructions, characterized in that When the computer program or instruction is executed by a processor, the method according to any one of claims 1 to 4 is implemented.

Images