CN204517612U - A kind of excitation adjustable permanent-magnet synchronous machine - Google Patents

Abstract

The utility model discloses an excitation-adjustable permanent-magnet synchronous motor, which comprises a rotor. The rotor includes a plurality of permanent magnet assemblies arranged in pairs. The permanent magnet assembly includes a cylindrical permanent magnet, a cover plate and a rotary drive mechanism. The cylindrical permanent magnets are magnetized in parallel, and a plurality of cylindrical permanent magnets are closely arranged in parallel; the cover plate has a rectangular parallelepiped structure and is made of magnetically permeable material, and the cylindrical permanent magnets are placed in the cover plate to form a rectangular parallelepiped permanent magnet; The rotation driving mechanism is connected with the cylindrical permanent magnet, and when the rotor rotates, it drives the cylindrical permanent magnet to rotate around its own axis, so that the magnetic flux of the permanent magnet assembly decreases. The utility model changes the rotor structure of the traditional permanent magnet synchronous motor so that the magnetic poles of the permanent magnet are pulled and rotated by the electromagnet in the motor, so that the excitation flux can be adjusted by itself, so that there is no need to apply a large demagnetization current component at high speed, which improves the motor efficiency.

Description

A permanent magnet synchronous motor with adjustable excitation

technical field

The utility model relates to the technical field of permanent magnet synchronous motors, in particular to an excitation-adjustable permanent magnet synchronous motor.

Background technique

The permanent magnet synchronous motor is a three-phase current in the stator winding of the motor. After the current is passed in, a rotating magnetic field will be formed in the stator winding of the motor. Since the permanent magnet is installed on the rotor, the magnetic pole of the permanent magnet is fixed. According to the principle of same-sex attraction and opposite-sex repulsion of magnetic poles, the rotating magnetic field generated in the stator will drive the rotor to rotate, and finally the rotation speed of the rotor is equal to the rotation speed of the rotating magnetic poles generated in the stator. Permanent magnet synchronous motors are often used as drives in electric vehicles.

The phase voltage u _s of the permanent magnet synchronous motor should be guaranteed not to exceed the limit value u _lim of the voltage:

u _s ² =u _d ² +u _q ² ≤u _lim ²

The above formula can be expressed as: (L _q i _q ) ² +(L _d i _d +ψ _f ) ² ≤(u _lim /ω _e ) ²

Among them, u _s is the phase voltage, u _d is the d-axis voltage component, u _q is the q-axis voltage component, u _lim is the limit voltage, L _d is the d-axis inductance, L _q is the q-axis inductance, ψ _f is the permanent magnet The generated flux linkage, ω _e is the rotational speed.

From the above formula of the permanent magnet synchronous motor AC-D axis mathematical model, it can be seen that when the motor speed increases, the phase voltage will increase. In order to ensure that the phase voltage does not exceed the limit voltage value, there are two methods: 1. You can increase the d-axis of the motor The demagnetization current component makes the d-axis armature reaction L _d i _d opposite to the permanent magnet flux linkage Ψ _f , so that the sum of the two decreases, that is, the purpose of magnetic field weakening speed-up is achieved. 2. The size of the excitation flux linkage can be reduced, but for the traditional permanent magnet synchronous motor, the magnetic flux emitted by the permanent magnet is fixed, so this method cannot be realized.

Since the permanent magnet synchronous motor is different from the electric excitation synchronous motor, when the input voltage of the electric excitation synchronous motor reaches the limit value, in order to make the motor rotate at a higher speed, it is necessary to reduce the excitation current of the motor. The excitation magnetomotive force of the permanent magnet synchronous motor is generated by the permanent magnet, so it cannot adjust its value by itself. During the speed regulation process of the permanent magnet synchronous motor, when the speed is higher than a certain speed, the field weakening control is required to maintain the balance between the counter electromotive force and the input voltage during high-speed rotation. The principle of field weakening control is to maintain the voltage balance during high-speed operation by adjusting the demagnetization current component of the stator direct axis when increasing the motor speed. But this method increases the current of the stator. And because in the traditional permanent magnet synchronous motor, the permeance of the permanent magnet is small, so the direct axis inductance is also small, so in the field weakening control, a large demagnetization current is required, which reduces the efficiency of the motor. In addition, excessive demagnetization current will also bring the danger of permanent magnet demagnetization. To sum up, if the permanent magnet synchronous motor can control the magnitude of the excitation flux by itself like the electric excitation synchronous motor, the control method can be simplified and the efficiency can be effectively improved.

Utility model content

The utility model designs and develops an excitation-adjustable permanent magnet synchronous motor. The purpose is to solve the problem that the permanent magnet of the existing permanent magnet synchronous motor has constant excitation, and when rotating at high speed, a demagnetization current must be applied to maintain the voltage balance. The structure of the permanent magnet synchronous motor that reduces the excitation magnetic field by itself.

Another purpose of this utility model is to provide a permanent magnet synchronous motor with adjustable excitation, which has a sliding rheostat that can adjust its resistance with the speed of rotation. To achieve the effect of changing the magnetic flux according to demand.

The technical scheme provided by the utility model is:

An excitation adjustable permanent magnet synchronous motor includes a rotor, the rotor includes several permanent magnet assemblies arranged in pairs, and the permanent magnet assemblies include:

A cylindrical permanent magnet, which adopts parallel magnetization, and the plurality of cylindrical permanent magnets are closely arranged in parallel;

The cover plate has a rectangular parallelepiped structure, the cover plate is made of a magnetically conductive material, and the cylindrical permanent magnet is placed in the cover plate to form a rectangular parallelepiped permanent magnet;

A rotary driving mechanism is connected with the cylindrical permanent magnet, and drives the cylindrical permanent magnet to rotate around its own axis when the rotor rotates, so that the magnetic flux of the permanent magnet assembly decreases.

Preferably, there are even numbers of cylindrical permanent magnets closely arranged in parallel in the permanent magnet assembly.

Preferably, the rotary drive mechanism includes:

a gear, which is coaxially and fixedly connected with the cylindrical permanent magnet;

a rack, which meshes with the gear to drive the gear to rotate;

The driver is connected with the rack and drives the rack to move so as to realize the rotation of the cylindrical permanent magnet around its axis.

Preferably, the driver includes:

A direct-acting electromagnet, which includes an electromagnet core and an armature, the armature is fixedly connected to the rack, an electromagnetic coil is wound on the electromagnet core, and the electromagnet core can generate electromagnetic force after being energized to attract the armature, Thereby driving the rack to move;

The return spring is connected with the rack, and drives the rack to reset after the electromagnetic force disappears.

Preferably, the driver includes:

a drive gear meshing with the rack;

The swing electromagnet includes an electromagnet core and an armature, the armature is coaxially connected with the rotation axis of the driving gear, an electromagnetic coil is wound on the electromagnet core, and the electromagnet core can generate electromagnetic force to attract the armature after electrification The rotation further drives the drive gear to rotate to realize the movement of the rack;

The return spring is connected with the drive gear, and drives the drive gear to reset after the electromagnetic force disappears.

Preferably, the electromagnetic coil is connected with a sliding rheostat, and the sliding rheostat rotates with the rotor, and the sliding rheostat has a slidable end, and the slidable end is connected with a resistance spring, and the slidable end can rotate with the rotor. The increase of the rotating speed continuously slides to the outside, and compresses the resistance spring, so that the resistance value of the sliding rheostat decreases, thereby increasing the current in the electromagnetic coil, increasing the electromagnetic force, thereby increasing the permanent The rotation angle of the magnet.

Preferably, the resistance value R of the sliding rheostat has the following relationship with the length x of the resistance in the access circuit:

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}\mathrm{<span\; class="notranslate">\; arccos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&CenterDot;</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}$

Among them, A and B are constants, F ₁ is the preload of the return spring, k ₁ is the stiffness coefficient of the return spring, F ₀ is the preload of the resistance spring, k ₀ is the stiffness coefficient of the resistance spring, m is the mass of the sliding end, R _z is the initial distance from the slidable end to the motor axis, _Rd is the radius of the pitch circle of the gear, and L is the total length of the resistance wire of the sliding rheostat.

Preferably, under the drive of the rotation drive mechanism, the rotation directions of the two adjacent cylindrical permanent magnets are opposite, so as to reduce the wear between the two adjacent cylindrical permanent magnets.

Preferably, the rotatable angle of the cylindrical permanent magnet is 0-45°.

An electric vehicle is driven by the above-mentioned excitation adjustable permanent magnet synchronous motor.

The beneficial effect of the excitation-adjustable permanent magnet synchronous motor described in the utility model is: the utility model changes the rotor structure of the traditional permanent magnet synchronous motor, so that the permanent magnet poles are pulled and rotated by the electromagnet in the motor, and the excitation magnetic flux can be adjusted by itself. Therefore, there is no need to apply a large demagnetization current component at high speed, which improves the efficiency of the motor, and the magnetic flux of the permanent magnet of the rotor can be changed correspondingly according to the speed requirement. At the same time, it also prevents the danger of permanent magnet demagnetization when the demagnetization current is too large, and the operation is simple, which is beneficial to control.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the excitation adjustable permanent magnet synchronous motor described in the utility model.

Fig. 2 is a schematic structural view of the permanent magnet assembly described in the present invention.

Fig. 3 is a schematic diagram of the magnetic flux passing through the permanent magnet assembly in the initial state of the present invention.

Fig. 4 is a schematic diagram of the magnetic flux passing through the permanent magnet assembly described in the present invention after the excitation is changed.

Fig. 5 is a schematic diagram of the driver transmission device described in the present invention.

Fig. 6 is a schematic diagram of the overall structure of the driver described in the present invention.

Fig. 7 is a schematic diagram of a transmission device in another embodiment of the driver according to the present invention.

Fig. 8 is a schematic structural diagram of the sliding rheostat described in the present invention.

Detailed ways

The utility model will be described in further detail below in conjunction with the accompanying drawings, so that those skilled in the art can implement it by referring to the description.

As shown in FIG. 1 , the utility model provides an excitation-adjustable permanent magnet synchronous motor, which includes a casing 1 , a stator 2 and a rotor 3 inside the casing 1 . There is an air gap between the inner surface of the stator 2 and the outer surface of the rotor 3, and the stator 2 is composed of a stator core and a stator winding. The rotor 3 includes a rotor core 4 , a motor shaft 5 , and permanent magnet assemblies 6 arranged in pairs. The motor shaft 5 is a through shaft made of magnetically isolated metal. The permanent magnet assembly 6 is placed in the through slot on the rotor core 4 , the permanent magnet assembly 6 forms a regular polygon at the end of the rotor 3 , and the center of the regular polygon is on the centerline of the rotor 3 . There are 2n permanent magnet assemblies, wherein the N poles of n permanent magnet assemblies 6 are vertically directed to the outside, and the N poles of the other n permanent magnet assemblies 6 are vertically directed to the inside, and the permanent magnet assemblies 6 are installed on the rotor core 4 in the rectangular through groove. According to the difference in polarity of each permanent magnet assembly, they are installed in the rectangular through slots of the rotor core 4 at intervals in sequence.

Referring to FIG. 2 together, the permanent magnet assembly 6 includes a cylindrical permanent magnet 610 , a cover plate 620 and a rotation driving mechanism 630 . The cylindrical permanent magnet 610 is magnetized in parallel, and a plurality of cylindrical permanent magnets are closely arranged in parallel from top to bottom without gaps between them. The cover plate 620 has a rectangular parallelepiped structure, and it is made of a magnetically conductive material. The cylindrical permanent magnet 610 is placed in the cover plate 620, and a cavity for accommodating the cylindrical permanent magnet 610 is provided in the cover plate 620. The cylindrical permanent magnet 610 and the An air gap of 0.1 mm is left between the cover plates 620 . A sliding bearing is installed at both ends of each cylindrical permanent magnet 610 , and each cylindrical permanent magnet 610 is installed in the cover plate 620 through the bushing of the sliding bearing. The material of the sliding bearings at both ends of each cylindrical permanent magnet 610 is a magnetic isolation metal material. The rotation driving mechanism 630 is connected with the cylindrical permanent magnet 610, and drives the cylindrical permanent magnet 610 to rotate around its own axis when the rotor 3 rotates, so as to reduce the magnetic flux of the permanent magnet assembly. Through this arrangement, when the excitation flux needs to be reduced in order to increase the rotating speed, the cylindrical permanent magnet 610 is rotated by a certain angle, which will reduce the magnetic flux in the original direction and increase the reverse magnetic flux by the same amount, realizing the weakening of the magnetic field. Purpose, as shown in Figure 3 and Figure 4.

In another embodiment, there is an even number of cylindrical permanent magnets 610 closely arranged in parallel in the permanent magnet assembly.

As shown in FIG. 5 and FIG. 6 , the rotary drive mechanism 630 in the above solution includes a gear 631 , a rack 632 and a driver. Wherein, the gear 631 is connected to the end surface of the cylindrical permanent magnet 610 and is coaxial with the cylindrical permanent magnet 610 . Rack 632 meshes with gear 631 as shown. The gears 631 are installed on both sides of the cylindrical permanent magnets 610 at intervals, that is, in the closely arranged cylindrical permanent magnets 610, the left side of the cylindrical permanent magnets 610 at odd positions is equipped with gears 631, and the cylindrical permanent magnets at even positions Gear 631 is installed on the right and left side of 610. Two racks 632 are provided, which are respectively located on the left and right sides of the cylindrical permanent magnet 610 and mesh with the gears 631 on both sides. The driver is connected to the rack 632 and can drive the rack 632 to move so as to realize the rotation of the cylindrical permanent magnet 610 around its own axis. The driver drives the two racks 632 to move in opposite directions, so that the two adjacent cylindrical permanent magnets 610 rotate in opposite directions, thereby reducing the wear between the two adjacent cylindrical permanent magnets 610 .

In another embodiment, the driver includes a direct-acting electromagnet, which includes an electromagnet core 641 and an armature 642, the armature 642 is fixedly connected to the rack 632, and an electromagnetic coil is wound on the electromagnet core 641 643. After electrification, the electromagnet core 641 can generate electromagnetic force to attract the armature 642, thereby driving the rack 632 to move. The driver also includes a reset spring 644, which is connected to the rack 632 and drives the rack to reset after the electromagnetic force disappears, so that the magnetic flux of the permanent magnet assembly returns to its original state. There are two drivers, which drive the two racks 632 in the same permanent magnet assembly 6 to move in opposite directions.

As shown in FIG. 7 , in another embodiment, the driver includes a driving gear 645 , a swing electromagnet and a return spring 644 . The drive gear 645 meshes with the rack 632; the swing electromagnet includes an electromagnet core and an armature, the armature is coaxially connected with the rotation axis of the drive gear, and an electromagnetic coil 643 is wound on the electromagnet core. The iron core can generate electromagnetic force to attract the armature to rotate and then drive the driving gear 645 to rotate to realize the movement of the rack 632; the return spring 644 is connected to the driving gear 645 to drive the driving gear 645 after the electromagnetic force disappears. The drive gear resets.

In another embodiment, the electromagnetic coil 643 is connected in series with a sliding rheostat 7, the sliding rheostat 7 rotates with the rotor, the sliding rheostat 7 has a slidable end 701, and the slidable end 701 is connected with a resistance spring 702 , under the action of the resistance spring 701, the sliding end 701 is pushed to the maximum resistance end of the sliding rheostat. At this time, the distance between the sliding end 701 and the motor axis is R _z . With the increase of the motor speed, under the action of centrifugal force The slidable end 701 will slide outward and compress the resistance spring 702 . Since the resistance spring 702 has an initial preload F ₀ , that is to say, the slidable end 701 will not slide outward when the rotation speed of the motor is small, only when the centripetal force of the slidable end 701 is greater than the initial preload F of the resistance spring 702 ₀ , the sliding end 701 will slide outward, that is, the motor speed ω needs to satisfy the following relationship

$\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; ></span>\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}}}<span\; class="notranslate">\; ,</span>$

Where m is the mass of the slidable end 701 .

As the speed of the motor increases, the sliding end 701 continues to move outward, so that the length of the resistor connected to the circuit is continuously reduced, and the resistance value is also continuously reduced, so that the current flowing through the electromagnetic coil 643 is continuously increased. The attraction force of the electromagnet is proportional to the current, and then the electromagnetic attraction force increases, causing the rack 632 to displace.

The attraction force F _d of the electromagnet satisfies the following relationship

F _d = F ₁ +k ₁ R _d θ,

Wherein, F ₁ is the preload of the return spring, k ₁ is the stiffness coefficient of the return spring, R _d is the radius of the pitch circle of the gear, and θ is the rotation angle of the cylindrical permanent magnet 610 .

And when the cylindrical permanent magnet 610 rotates the angle θ, the magnetic flux φ passing through the permanent magnet assembly 6 is

φ=BScosθ

Where B is the magnetic field strength, and S is the frontal area of the permanent magnet assembly.

It can be seen that when the cylindrical permanent magnet 610 is rotated by the angle θ, the magnetic flux passing through the permanent magnet assembly 6 will decrease, thereby reducing the effect of the counter electromotive force and further increasing the speed of the motor. As the rotational speed continues to increase, the θ angle also needs to increase accordingly to reduce more magnetic flux.

The relationship between the resistance value R of the sliding rheostat and the length x of the resistance in the access circuit can be expressed as:

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}\mathrm{<span\; class="notranslate">\; arccos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}$

Among them, A and B are constants, F ₁ is the preload of the return spring, k ₁ is the stiffness coefficient of the return spring, F ₀ is the preload of the resistance spring, k ₀ is the stiffness coefficient of the resistance spring, and R _z is the initial sliding end The distance from the axis of the motor, R _d is the radius of the pitch circle of the gear, and L is the total length of the resistance wire of the sliding rheostat.

In the above formula, the constant A is Euler's number, that is, A=e=2.71828, and the constant B=0.5.

As a preferred embodiment, the rotatable angle of the cylindrical permanent magnet 610 is 0-45°.

Although the embodiment of the present utility model has been disclosed as above, it is not limited to the use listed in the description and the implementation, and it can be applied to various fields suitable for the present utility model. For those familiar with the art, Further modifications can be readily effected, so the invention is not limited to the specific details and examples shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims (10)

1. An excitation adjustable permanent magnet synchronous motor, comprising a rotor, the rotor comprising several permanent magnet assemblies arranged in pairs, characterized in that, the permanent magnet assembly comprises: A cylindrical permanent magnet, which adopts parallel magnetization, and the plurality of cylindrical permanent magnets are closely arranged in parallel; The cover plate has a rectangular parallelepiped structure, the cover plate is made of a magnetically conductive material, and the cylindrical permanent magnet is placed in the cover plate to form a rectangular parallelepiped permanent magnet; A rotary driving mechanism is connected with the cylindrical permanent magnet, and drives the cylindrical permanent magnet to rotate around its own axis when the rotor rotates, so that the magnetic flux of the permanent magnet assembly decreases. 2. The excitation adjustable permanent magnet synchronous motor according to claim 1, characterized in that there are even numbers of cylindrical permanent magnets closely arranged in parallel in the permanent magnet assembly. 3. The excitation adjustable permanent magnet synchronous motor according to claim 1 or 2, wherein the rotary drive mechanism comprises: a gear, which is coaxially and fixedly connected with the cylindrical permanent magnet; a rack, which meshes with the gear to drive the gear to rotate; The driver is connected with the rack and drives the rack to move so as to realize the rotation of the cylindrical permanent magnet around its axis. 4. The excitation adjustable permanent magnet synchronous motor according to claim 3, wherein the driver comprises: A direct-acting electromagnet, which includes an electromagnet core and an armature, the armature is fixedly connected to the rack, an electromagnetic coil is wound on the electromagnet core, and the electromagnet core can generate electromagnetic force after being energized to attract the armature, Thereby driving the rack to move; The return spring is connected with the rack, and drives the rack to reset after the electromagnetic force disappears. 5. The excitation adjustable permanent magnet synchronous motor according to claim 3, wherein the driver comprises: a drive gear meshing with the rack; The swing electromagnet includes an electromagnet core and an armature, the armature is coaxially connected with the rotation axis of the driving gear, an electromagnetic coil is wound on the electromagnet core, and the electromagnet core can generate electromagnetic force to attract the armature after electrification Rotate and then drive the drive gear to rotate to realize the movement of the rack; The return spring is connected with the drive gear, and drives the drive gear to reset after the electromagnetic force disappears. 6. The excitation adjustable permanent magnet synchronous motor according to claim 4 or 5, wherein the electromagnetic coil is connected with a sliding rheostat, and the sliding rheostat rotates with the rotor, and the sliding rheostat has a slidable end , the slidable end is connected with a resistance spring, and the slidable end can continuously slide outward with the increase of the rotor speed, and compress the resistance spring to reduce the resistance of the sliding rheostat, thereby increasing the The current in the electromagnetic coil increases the electromagnetic force, thereby increasing the rotation angle of the cylindrical permanent magnet. 7. The excitation adjustable permanent magnet synchronous motor according to claim 6, wherein the resistance value R of the sliding rheostat has the following relationship with the length x of the resistance in the access circuit: Among them, A and B are constants, F ₁ is the preload of the return spring, k ₁ is the stiffness coefficient of the return spring, F ₀ is the preload of the resistance spring, k ₀ is the stiffness coefficient of the resistance spring, and R _z is the initial sliding end The distance from the axis of the motor, R _d is the radius of the pitch circle of the gear, and L is the total length of the resistance wire of the sliding rheostat. 8. The field-adjustable permanent magnet synchronous motor according to claim 4 or 5, characterized in that, under the drive of the rotary drive mechanism, the rotation directions of the two adjacent cylindrical permanent magnets are opposite to reduce the Wear between two adjacent cylindrical permanent magnets. 9. The excitation adjustable permanent magnet synchronous motor according to claim 7, characterized in that, the rotatable angle of the cylindrical permanent magnet is 0-45°. 10. An electric vehicle, characterized in that it is driven by the adjustable excitation permanent magnet synchronous motor according to any one of claims 1-9.