Magnetic linkage adjustable motor and control method thereof

Abstract

The invention provides a flux linkage adjustable motor and a control method thereof, the motor comprises a stator core and a rotor, and the stator core and the rotor are oppositely arranged; the stator core is connected with a pushing mechanism, and the pushing mechanism is used for pushing the stator core to move so as to adjust the coincidence length of the stator core and the rotor and change the flux linkage of the motor. The pushing mechanism pushes the stator iron core to move axially, so that the stator iron core and the rotor which are oppositely arranged move relatively to change the coincidence length of the stator iron core and the rotor, thereby changing the flux linkage of the motor. The flux linkage of the motor is changed in the running process of the motor, the back electromotive force of the motor can be prevented from being larger than the bus voltage when the motor runs at a high rotating speed, and the efficiency of the motor running at the high rotating speed is improved. Compared with field weakening control, the maximum operation rotating speed of the motor can be increased, demagnetization current does not need to be increased, and motor demagnetization is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a flux-adjustable motor and a control method thereof. Background Art

[0002] With the continuous development of power electronics technology, material science and control theory, motors are widely used in rail transportation, equipment manufacturing, new energy, national defense and military industries, etc. Permanent magnet synchronous motors have the advantages of high power and torque density, small size, simple structure and wide speed regulation range.

[0003] For new energy electric vehicles, the performance requirements for the drive motor system vary under different working conditions. When the car starts to accelerate from a standstill or low speed, or when starting on a slope, the vehicle speed or motor speed is relatively low, and a large torque is required to overcome the friction or the weight of the car itself. Since the output electromagnetic torque of the permanent magnet synchronous motor is proportional to the magnetic flux, and the magnetic flux is proportional to the back electromotive force of the motor, the motor needs a larger back electromotive force at low speed.

[0004] When the car is cruising at high speed, the system usually does not require high torque, but in order to make the car's drive motor run at high speed, the motor needs to be weakly controlled by the controller. Due to the limited voltage level of the on-board battery, the back electromotive force generated by the permanent magnet in the permanent magnet motor increases with the increase of speed. When the back electromotive force is greater than the bus voltage, the motor speed cannot continue to increase. At this time, the more commonly used method is to increase the direct-axis demagnetization current through weak magnetic control, but this will increase losses, and in the case of deep weak magnetic, the permanent magnet is also at risk of demagnetization, resulting in a smaller range of weak magnetic speed expansion for the motor. Summary of the invention

[0005] In order to overcome the problems existing in the related art, one of the objects of the present invention is to provide a motor with adjustable flux, which drives the stator core to move, so that the overlap length between the stator core and the rotor changes, thereby reducing the motor flux, thereby reducing the back electromotive force of the motor, and preventing the back electromotive force of the motor from exceeding the bus voltage at high speed, so that the motor can be controlled by the maximum torque current ratio control method at different speeds, which is more efficient in the high speed stage than weak magnetic control.

[0006] A motor with adjustable flux linkage comprises a stator core and a rotor, wherein the stator core and the rotor are arranged facing each other; the stator core is connected to a driving mechanism, and the driving mechanism is used to drive the stator core to move so as to adjust the overlapping length between the stator core and the rotor and change the flux linkage of the motor.

[0007] The present invention changes the magnetic flux of the motor during operation, which can prevent the back electromotive force of the motor from being greater than the bus voltage when the motor is running at a high speed, thereby improving the efficiency of the motor when running at a high speed. Compared with weak magnetic control, the present invention can increase the maximum operating speed of the motor without increasing the demagnetization current, thereby avoiding motor demagnetization.

[0008] In a preferred technical solution of the present invention, the adjustable flux motor further includes a casing, the stator core is sleeved in the casing, and the stator core can move axially in the casing.

[0009] The casing protects the stator core, and the stator core can move axially relative to the casing.

[0010] In a preferred technical solution of the present invention, the stator core includes a yoke, the yoke is an annular structure, and a slide groove is arranged on the outer side of the yoke.

[0011] The yoke of the stator core is arranged as a circular ring structure, and a plurality of slide grooves are evenly distributed on the outer side of the yoke.

[0012] In a preferred technical solution of the present invention, a sliding key is provided on a side of the housing close to the stator core, and the sliding key is inserted into the sliding groove.

[0013] The sliding key is inserted into the sliding groove, and the stator core is fixed in the casing under the cooperation of the sliding key and the sliding groove. Under the condition of ensuring that the stator core is circumferentially fixed, the stator core can only move axially relative to the casing.

[0014] In a preferred technical solution of the present invention, the stator core further includes a plurality of teeth, and the plurality of teeth are circumferentially arranged on the inner side of the yoke.

[0015] The slide grooves are arranged at positions corresponding to some teeth on the outer side of the stator core, and the number of the slide grooves is less than the number of the teeth.

[0016] In a preferred technical solution of the present invention, a plurality of the slide grooves are circumferentially spaced apart on the outer side of the yoke, and the slide grooves extend along the axial direction of the stator core.

[0017] A plurality of slide grooves are provided, and each slide key is inserted into a corresponding slide groove. Under the joint action of the plurality of slide grooves and the plurality of slide keys, it is ensured that the stator core can move axially while being fixed in the circumferential direction.

[0018] In a preferred technical solution of the present invention, the pushing mechanism includes any one or any combination of a cylinder and a push rod.

[0019] The stator core is driven to move axially by a cylinder and / or a push rod.

[0020] In a preferred technical solution of the present invention, the slide groove and the tooth portion are arranged opposite to each other, and the width of the slide groove is smaller than the width of the tooth portion.

[0021] The width of the slide slot is smaller than the width of the tooth portion, which can prevent the yoke portion of the stator core from being oversaturated and avoid a decrease in motor efficiency.

[0022] In a preferred technical solution of the present invention, stator slots are provided between adjacent teeth, and the stator slots are used to accommodate coil windings.

[0023] The teeth are spaced apart from the stator slots, that is, stator slots are respectively arranged on both sides of one tooth.

[0024] A second object of the present invention is to provide a motor control method, based on any one of the above-mentioned adjustable flux motors, the method comprising:

[0025] Obtaining the motor speed, if the motor speed is greater than the rated speed, the driving mechanism drives the stator core to move axially;

[0026] The maximum torque current ratio control method is adopted to control the adjustable flux motor.

[0027] When the motor speed is greater than the rated speed n N When the controller controls the driving mechanism to drive the stator core to move axially L M , so that the overlap length of the stator core and the rotor becomes LL M , at the same speed, the back electromotive force changes from E to E(LL M ) / L. When guaranteed (LL M )n≤n N L, the back electromotive force of the motor in the entire speed range is less than the bus voltage, and the motor can always use the maximum torque current ratio control method, thereby improving the motor efficiency when the motor speed is greater than the rated speed. Since this embodiment does not use weak magnetic control, when the motor speed is greater than the rated speed, the demagnetization current will not be too large to cause the motor to demagnetize, further increasing the speed range.

[0028] In a preferred technical solution of the present invention, after obtaining the motor speed, the method further includes:

[0029] If the motor speed is less than or equal to the rated speed, the maximum torque current ratio control method is used to control the adjustable flux motor.

[0030] When the motor is in the low-speed operation stage, the driving mechanism does not push the stator core. At this time, the overlapping length of the stator core and the rotor is the largest, and the maximum overlapping length is L, which can ensure that the motor outputs sufficient torque under low-speed and heavy-load conditions.

[0031] The beneficial effects of the present invention are:

[0032] The present invention provides a motor with adjustable flux, including a stator core and a rotor, wherein the stator core and the rotor are arranged facing each other; the stator core is connected to a driving mechanism, and the driving mechanism is used to drive the stator core to move, so as to adjust the overlapping length of the stator core and the rotor, and change the flux of the motor. The driving mechanism drives the stator core to move, so that the stator core and the rotor arranged facing each other move relative to each other, so as to change the overlapping length of the stator core and the rotor, thereby changing the flux of the motor. The present invention changes the flux of the motor during the operation of the motor, and can prevent the back electromotive force of the motor from being greater than the bus voltage when the motor is running at a high speed, thereby improving the efficiency of the motor when running at a high speed. Compared with weak magnetic control, the present invention can increase the maximum operating speed of the motor without increasing the demagnetization current, thereby avoiding motor demagnetization. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of the flux-adjustable motor of the present invention;

[0034] Figure 2 It is a schematic diagram of the structure of the stator core and the casing after being assembled in the present invention;

[0035] Figure 3 It is a structural schematic diagram of the stator core of the present invention;

[0036] Figure 4 It is a structural schematic diagram of the casing of the present invention;

[0037] Figure 5 is a flow chart of a motor control method of the present invention;

[0038] Figure 6 It is the TN curve of the weak magnetic expansion permanent magnet motor;

[0039] Figure 7 It is the TN curve of the flux-adjustable motor of the present invention.

[0040] Figure numerals: 1. stator core; 2. rotor; 3. driving mechanism; 4. housing; 5. yoke; 6. slide groove; 7. slide key; 8. tooth; 9. stator slot. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0042] Example 1

[0043] like Figure 1 and Figure 2 As shown, this embodiment provides a motor with adjustable flux, including a stator core 1 and a rotor 2, wherein the stator core 1 and the rotor 2 are arranged opposite to each other; the stator core 1 is connected to a driving mechanism 3, and the driving mechanism 3 is used to drive the stator core 1 to move, so as to adjust the overlapping length of the stator core 1 and the rotor 2 and change the flux of the motor.

[0044] The rotor 2 is fixed in the housing 4 by bearings and end covers, and a stator core 1 is arranged above the rotor 2, with a gap between the stator core 1 and the rotor 2. The stator core 1 and the rotor 2 are arranged facing each other, and when the stator core 1 is in the initial position, that is, the stator core 1 does not have a relative displacement with the rotor 2, the overlap length between the stator core 1 and the rotor 2 is the largest, and the maximum overlap length is L. The stator core 1 is projected onto the plane where the rotor 2 is located, and the projection area can be obtained. The length of the overlapping part of the projection area and the area where the stator core 1 is located is the overlap length.

[0045] The driving mechanism 3 is fixedly connected to the first end of the stator core 1, and the driving mechanism 3 can drive the stator core 1 to move axially, thereby changing the overlap length between the stator core 1 and the rotor 2. When the adjustable flux motor runs at a low speed, the back electromotive force E of the adjustable flux motor is less than the bus voltage U. The maximum torque current ratio control method, i.e., the MTPA method, is used to control the adjustable flux motor, so that the current corresponding to the unit torque of the adjustable flux motor is minimized and the motor efficiency is the highest. When the adjustable flux motor runs at a high speed, as the motor speed increases, the back electromotive force of the adjustable flux motor increases proportionally. At this time, the back electromotive force E> the bus voltage U. If the maximum torque current ratio control method is still used for control, the adjustable flux motor will not work.

[0046] In this embodiment, when the adjustable flux motor is running at high speed, the driving mechanism 3 drives the stator core 1 to move axially, thereby reducing the overlap length of the stator core 1 and the rotor 2. When other conditions remain unchanged, the motor flux is approximately proportional to the overlap length of the stator core 1 and the rotor 2, that is, the greater the overlap length of the stator core 1 and the rotor 2, the greater the motor flux. Therefore, under the condition of the same motor speed, reducing the overlap length of the stator core 1 and the rotor 2 can reduce the back electromotive force E of the adjustable flux motor, ensuring that the back electromotive force E of the adjustable flux motor is less than the bus voltage U in the entire speed range.

[0047] The traditional solution is to use the MTPV control strategy when the motor is running at high speed, and to perform weak magnetic control on the motor by increasing the direct-axis demagnetization current of the motor, which increases the loss of the motor and reduces the efficiency of the motor. When the demagnetization current is too large, it is easy to cause the motor to demagnetize, and the speed range is limited. This embodiment reduces the back electromotive force E of the adjustable flux motor by adjusting the overlap length of the stator core 1 and the rotor 2, without increasing the direct-axis demagnetization current, and can avoid motor demagnetization. Figure 6It is the TN curve of the weak magnetic expansion permanent magnet motor. Figure 7 is the TN curve of the flux-adjustable motor of this embodiment. The TN curve is a curve that describes the relationship between the motor torque and speed. Figure 6 and Figure 7 The horizontal axis is the rotation speed, and the unit of rotation speed is rpm, that is, the number of rotations of the motor per minute. Figure 6 and Figure 7 The vertical axis in the figure is torque, and the unit of torque is Nm. Figure 6 As shown in FIG. 1 , the adjustable range of the motor speed corresponding to the weak magnetic control is 0-7000 rpm. Figure 7 As shown, the adjustable speed range of the flux linkage adjustable motor of this embodiment is 0-14000rpm. Compared with the motor controlled by the weak magnetic control method, the flux linkage adjustable motor of this embodiment has a wider speed range, especially in the high speed stage, the speed range that can be selected is wider, which is suitable for various application scenarios with different requirements for speed.

[0048] The present embodiment provides a motor with adjustable flux, including a stator core 1 and a rotor 2, wherein the stator core 1 and the rotor 2 are arranged opposite to each other; the stator core 1 is connected to a driving mechanism 3, and the driving mechanism 3 is used to drive the stator core 1 to move, so as to adjust the overlapping length of the stator core 1 and the rotor 2, and change the flux of the motor. The driving mechanism 3 drives the stator core 1 to move, so that the stator core 1 and the rotor 2 arranged opposite to each other move relative to each other, so as to change the overlapping length of the stator core 1 and the rotor 2, thereby changing the flux of the motor. The present invention changes the flux of the motor during the operation of the motor, and can prevent the back electromotive force of the motor from being greater than the bus voltage when the motor is running at a high speed, thereby improving the efficiency of the motor when running at a high speed. Compared with weak magnetic control, the present invention can increase the maximum operating speed of the motor without increasing the demagnetization current to avoid motor demagnetization.

[0049] Example 2

[0050] like Figure 1 and Figure 2 As shown, this embodiment provides a motor with adjustable flux, including a stator core 1 and a rotor 2, wherein the stator core 1 and the rotor 2 are arranged opposite to each other; the stator core 1 is connected to a driving mechanism 3, and the driving mechanism 3 is used to drive the stator core 1 to move, so as to adjust the overlapping length of the stator core 1 and the rotor 2 and change the flux of the motor.

[0051] The adjustable flux linkage motor further comprises a casing 4 , wherein the stator core 1 is sleeved in the casing 4 , and the stator core 1 can move axially in the casing 4 .

[0052] like Figure 3 As shown, the stator core 1 includes a yoke 5 , which is an annular structure, and a slide groove 6 is arranged on the outer side of the yoke 5 .

[0053] like Figure 4 As shown, a sliding key 7 is provided on one side of the housing 4 close to the stator core 1 , and the sliding key 7 is inserted into the sliding groove 6 .

[0054] The yoke 5 of the stator core 1 is set as a circular ring structure, and a plurality of chute 6 is evenly distributed on the outer side of the yoke 5, that is, on the side of the yoke 5 away from the middle of the stator core 1. There are many ways to open the chute 6, and the chute 6 can be directly opened on the outer side of the yoke 5 of the stator core 1, or the chute 6 can be opened after adding a steel sleeve on the outer side of the yoke 5, which is not limited here.

[0055] A plurality of sliding keys 7 are provided on the inner side of the housing 4, i.e., the side of the housing 4 facing the stator core 1, and the sliding keys 7 are adapted to the slide grooves 6. The sliding keys 7 are inserted into the slide grooves 6, and the stator core 1 is fixed in the housing 4 under the cooperation of the sliding keys 7 and the slide grooves 6, so that the stator core 1 can only move axially relative to the housing 4 while ensuring that the stator core 1 is fixed circumferentially.

[0056] The magnetic flux adjustable motor of this embodiment also includes a casing 4, and the stator core 1 is sleeved in the casing 4, and the stator core 1 can move axially in the casing 4. The stator core 1 includes a yoke 5, and the yoke 5 is an annular structure, and a slide groove 6 is arranged on the outer side of the yoke 5. A sliding key 7 is provided on the side of the casing 4 close to the stator core 1, and the sliding key 7 is inserted into the slide groove 6. The pushing mechanism 3 pushes the stator core 1, and the slide groove 6 of the stator core 1 cooperates with the sliding key 7 of the casing 4, so that the stator core 1 moves axially relative to the casing 4. The provision of the sliding key 7 and the slide groove 6 that cooperate with each other not only increases the contact area between the stator core 1 and the casing 4, improves the heat dissipation capacity of the motor, but also changes the overlap length of the stator core 1 and the rotor 2, further adjusts the magnetic flux of the whole machine, increases the speed range of the motor, and thus improves the motor efficiency in the high-speed operation area.

[0057] Example 3

[0058] like Figure 1 and Figure 2 As shown, this embodiment provides a motor with adjustable flux, including a stator core 1 and a rotor 2, wherein the stator core 1 and the rotor 2 are arranged opposite to each other; the stator core 1 is connected to a driving mechanism 3, and the driving mechanism 3 is used to drive the stator core 1 to move, so as to adjust the overlapping length of the stator core 1 and the rotor 2 and change the flux of the motor.

[0059] like Figure 3 As shown, the stator core 1 includes a yoke 5 , which is an annular structure, and a slide groove 6 is arranged on the outer side of the yoke 5 .

[0060] like Figure 4As shown, a sliding key 7 is provided on one side of the housing 4 close to the stator core 1 , and the sliding key 7 is inserted into the sliding groove 6 .

[0061] A plurality of the slide grooves 6 are circumferentially spaced apart from each other on the outer side of the yoke 5 , and the slide grooves 6 extend along the axial direction of the stator core 1 .

[0062] The pushing mechanism 3 includes any one or any combination of a cylinder and a push rod.

[0063] The pushing mechanism 3 can be any one structure or any multiple structures such as an oil cylinder, an air cylinder, a screw rod, a spring, etc., which is not limited here.

[0064] When the pushing mechanism 3 is a cylinder, the telescopic rod of the cylinder is fixedly connected to the stator core 1. After the cylinder is started, the telescopic rod of the cylinder extends, driving the stator core 1 to move axially.

[0065] When the pushing mechanism 3 is a push rod, the push rod can be pushed manually or electrically. Here, an electric push rod is preferably used to drive the stator core 1 to move axially, which has a better pushing effect and higher efficiency.

[0066] When the pushing mechanism 3 is a combination of a cylinder and a push plate, the telescopic rod of the cylinder is connected to the push plate, and the push plate is fixedly connected to one end of the stator core 1. After the cylinder is started, the telescopic rod is extended, and the telescopic rod drives the push plate to push the stator core 1 to move axially. The contact area between the push plate and the stator core 1 is larger, and the pushing effect is better.

[0067] In this embodiment, the plurality of slide grooves 6 are circumferentially spaced apart on the outside of the yoke 5, and the slide grooves 6 extend along the axial direction of the stator core 1. The pushing mechanism 3 includes any one or any combination of a cylinder and a push rod. If the pushing mechanism 3 is an electric push rod, the electric push rod drives the stator core 1 to move axially, and the slide groove 6 of the yoke 5 of the stator core 1 cooperates with the slide key 7 of the housing 4. The slide key 7 is inserted into the slide groove 6, so that the stator core 1 moves axially relative to the housing 4. The position of the stator core 1 changes, thereby changing the overlapping length of the stator core 1 and the rotor 2, causing the magnetic flux of the motor to change, thereby improving the speed expansion capability of the motor. Compared with weak magnetic control, the method of adjusting the magnetic flux can improve the motor efficiency in the high-speed operation area and reduce motor losses.

[0068] Example 4

[0069] like Figure 1 and Figure 2As shown, this embodiment provides a motor with adjustable flux, including a stator core 1 and a rotor 2, wherein the stator core 1 and the rotor 2 are arranged opposite to each other; the stator core 1 is connected to a driving mechanism 3, and the driving mechanism 3 is used to drive the stator core 1 to move, so as to adjust the overlapping length of the stator core 1 and the rotor 2 and change the flux of the motor.

[0070] like Figure 3 As shown, the stator core 1 includes a yoke 5 , which is an annular structure, and a slide groove 6 is arranged on the outer side of the yoke 5 .

[0071] The stator core 1 further includes a plurality of teeth 8 , which are circumferentially arranged on the inner side of the yoke 5 .

[0072] The chute 6 is arranged opposite to the tooth 8, and the width of the chute 6 is smaller than the width of the tooth 8. The chute 6 is arranged at a position corresponding to a part of the tooth 8 on the outside of the stator core 1, and the number of the chute 6 is smaller than the number of the tooth 8. If the width of the chute 6 is greater than the width of the tooth 8, or the position of the chute 6 is incorrectly set, the yoke 5 of the stator core 1 will be oversaturated, resulting in a decrease in motor efficiency.

[0073] Stator slots 9 are provided between adjacent teeth 8, and the stator slots 9 are used to accommodate coil windings. There are two options for the position of the chute 6, the first is to provide the chute 6 at a position opposite to the teeth 8, and the second is to provide the chute 6 at a position corresponding to the stator slot 9. If the chute 6 is provided at a position corresponding to the stator slot 9, both the inner and outer rings of the stator core 1 are provided with slots, and the remaining area of ​​the yoke 5 is relatively small, so that the magnetic circuit is oversaturated, resulting in a significant decrease in magnetic permeability. Therefore, in this embodiment, the chute 6 is provided on the side of the yoke 5 away from the stator core 1 and at a position opposite to the teeth 8. The remaining area of ​​the yoke 5 is relatively large, which can prevent the magnetic circuit from being oversaturated, so that the influence of the chute 6 on the magnetic permeability is relatively small.

[0074] The stator slot 9 is provided with a coil winding, which may be an L-shaped coil winding or other types of coil windings. The present embodiment takes the L-shaped coil winding as an example.

[0075] The tooth portion 8 and the stator slot 9 are arranged at intervals, that is, a stator slot 9 is arranged on both sides of a tooth portion 8. The first end of the stator slot 9 is connected to the tooth portion 8, and the stator slot 9 extends radially from the first end in a direction away from the middle of the stator core 1. The first end of the stator slot 9 is at the smallest distance from the middle of the stator core 1, and the second end of the stator slot 9 is at the largest distance from the middle of the stator core 1. From the first end to the second end of the stator slot 9, the size of the stator slot 9 gradually increases.

[0076] The stator core 1 of this embodiment further includes a plurality of teeth 8, and the plurality of teeth 8 are circumferentially arranged on the inner side of the yoke 5. The chute 6 is arranged opposite to the teeth 8, and the width of the chute 6 is smaller than the width of the teeth 8. Stator slots 9 are provided between adjacent teeth 8, and the stator slots 9 are used to accommodate coil windings. The chute 6 is provided on the side of the yoke 5 away from the stator core 1 and at a position opposite to the teeth 8. The remaining area of ​​the yoke 5 is large, which can prevent the magnetic circuit from being oversaturated, so that the chute 6 has a smaller effect on the magnetic permeability.

[0077] Example 5

[0078] like Figure 5 As shown, this embodiment provides a material automatic assembly method, based on the adjustable flux motor of any one of Embodiments 1 to 4, the method includes:

[0079] S1: Get the motor speed.

[0080] S2: If the motor speed is greater than the rated speed, the driving mechanism drives the stator core to move axially.

[0081] S3: The maximum torque current ratio control method is adopted to control the adjustable flux motor.

[0082] After obtaining the motor speed, the method further includes:

[0083] S4: If the motor speed is less than or equal to the rated speed, the maximum torque current ratio control method is used to control the adjustable flux motor.

[0084] Step S2 is parallel to step S4. If the motor speed is greater than the rated speed, steps S2-S3 are executed; if the motor speed is less than or equal to the rated speed, step S4 is executed.

[0085] Permanent magnet motor flux calculation formula: Where Ψ is the flux linkage, N is the number of coil turns, For magnetic flux.

[0086] The calculation formula of back electromotive force of permanent magnet motor is: E=4.44fΨ, where E is back electromotive force, f is frequency, and Ψ is magnetic flux.

[0087] When the motor is in the low-speed operation stage, that is, the motor speed is less than or equal to the rated speed n N When the motor back electromotive force E is lower than the bus voltage U, the maximum torque current ratio control method is used to control the motor. The current corresponding to the unit torque is the smallest and the motor efficiency is the highest. As the motor speed increases, when the motor speed is greater than the rated speed n NWhen the back electromotive force E increases in proportion to the speed, if the maximum torque current ratio control method is still used to control the motor, when the back electromotive force E>bus voltage U, the motor cannot work.

[0088] The motor control method of this embodiment is that when the motor is in the low-speed operation stage, the driving mechanism 3 does not drive the stator core 1. At this time, the overlap length of the stator core 1 and the rotor 2 is the largest, and the maximum overlap length is L, which can ensure that the motor outputs sufficient torque under low-speed and heavy-load conditions. Under certain other conditions, the motor flux is approximately proportional to L, so shortening L at the same speed can reduce the motor's back electromotive force E. When the motor speed is greater than the rated speed n N When the controller controls the driving mechanism 3 to drive the stator core 1 to move axially L M , so that the overlap length of the stator core 1 and the rotor 2 becomes LL M , at the same speed, the back electromotive force changes from E to E(LL M ) / L. When guaranteed (LL M )n≤n N L, the back electromotive force of the motor in the entire speed range is less than the bus voltage, and the motor can always use the maximum torque current ratio control method, thereby improving the motor efficiency when the motor speed is greater than the rated speed. Since this embodiment does not use weak magnetic control, when the motor speed is greater than the rated speed, the demagnetization current will not be too large to cause the motor to demagnetize, further increasing the speed range.

[0089] Preferably, the stator core 1 is moved in stages to ensure the convenience of control, with slight magnetic weakening in the overspeed stage and the stator core 1 being moved again in the deep magnetic weakening stage. This solution can further increase the speed expansion range.

[0090] This embodiment provides a motor control method. When the motor speed is low, the overlap length of the stator core 1 and the rotor 2 is the maximum, and the maximum overlap length is L. When the motor speed is greater than the rated speed n N When the driving mechanism 3 is controlled to drive the stator core 1 to move axially, the overlapping length of the stator core 1 and the rotor 2 becomes LL M , at the same speed, the back electromotive force changes from E to E(LL M ) / L, so that the back electromotive force E of the motor is less than the bus voltage, and the maximum torque current ratio control method can be used to control the motor, thereby improving the motor efficiency when the motor speed is greater than the rated speed. Since the embodiment does not use weak magnetic control, when the motor speed is greater than the rated speed, the demagnetization current is not too large to cause the motor to demagnetize, further increasing the speed range.

[0091] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the application. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a restriction. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in the subsequent accompanying drawings.

[0092] It should be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would then be positioned "below" or "below" the other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used herein should be interpreted accordingly.

[0093] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A motor with adjustable flux linkage, characterized in that: It comprises a stator core and a rotor, wherein the stator core and the rotor are arranged facing each other; the stator core is connected with a driving mechanism, and the driving mechanism is used to drive the stator core to move so as to adjust the overlapping length between the stator core and the rotor and change the magnetic flux of the motor.

2. The flux-adjustable motor according to claim 1, characterized in that: It also includes a casing, the stator core is sleeved in the casing, and the stator core can move axially in the casing.

3. The flux-adjustable motor according to claim 2, characterized in that: The stator core comprises a yoke, which is an annular structure, and a sliding groove is arranged on the outer side of the yoke.

4. The flux-adjustable motor according to claim 3, characterized in that: A sliding key is provided on one side of the housing close to the stator core, and the sliding key is inserted into the sliding groove.

5. The flux-adjustable motor according to claim 3, characterized in that: The stator core further includes a plurality of teeth, which are circumferentially arranged on the inner side of the yoke.

6. The flux-adjustable motor according to claim 3, characterized in that: A plurality of the slide grooves are circumferentially spaced apart and arranged outside the yoke, and the slide grooves extend along the axial direction of the stator core.

7. The flux-adjustable motor according to claim 1, characterized in that: The pushing mechanism includes any one or any combination of a cylinder and a push rod.

8. The flux-adjustable motor according to claim 5, characterized in that: The slide groove is arranged opposite to the tooth portion, and the width of the slide groove is smaller than the width of the tooth portion.

9. The flux-adjustable motor according to claim 5, characterized in that: Stator slots are provided between adjacent teeth, and the stator slots are used to accommodate coil windings.

10. A motor control method, characterized in that: Based on the adjustable flux motor according to any one of claims 1 to 9, the method comprises: Get the motor speed; If the motor speed is greater than the rated speed, the driving mechanism drives the stator core to move axially; The maximum torque current ratio control method is adopted to control the adjustable flux motor.

11. The motor control method according to claim 10, characterized in that: After obtaining the motor speed, the method further includes: If the motor speed is less than or equal to the rated speed, the maximum torque current ratio control method is used to control the adjustable flux motor.

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