Radial magnetic field anti-salient permanent magnet synchronous motor system

Abstract

A radial magnetic field reverse-salient pole permanent magnet synchronous motor system relates to the field of electric motors. It addresses the problem that traditional permanent magnet synchronous motors cannot simultaneously increase output torque and expand the constant power speed regulation range. The stator core's outer circumference is provided with multiple axial slots, with both the power winding and the field control winding embedded in the slots. The power winding is connected to an AC power supply, while the field control winding is connected to the AC power supply via an excitation power converter. The rotor core is provided with 2P first through-hole groups and 2P second through-hole groups, with a permanent magnet embedded in each second through-hole. The magnetic lines of force generated by the direct-axis current in the field control winding are aligned with those generated by the permanent magnets, and the direct-axis synchronous inductance is greater than the quadrature-axis synchronous inductance. When the motor is operating below base speed, the excitation power converter outputs an AC current to the field control winding, causing the direct-axis component of the field control winding current to remain constant and greater than zero. Conversely, the direct-axis component of the field control winding current decreases as the motor speed increases.

Description

Technical Field

[0001] The present invention belongs to the field of motors, and in particular relates to a rotor structure of a motor. Background Art

[0002] In modern industry, variable-frequency drives (VFDs) are increasingly being used as their overall performance continues to improve. Permanent-magnet synchronous motors (PMSMs), with their advantages of high efficiency, high power factor, and high power density, are increasingly being used in electric drive systems. However, when PMSMs operate above base speed, their back EMF increases proportionally with speed. This, combined with power supply voltage limitations and current controller saturation, restricts further expansion of their speed range. Increasing the direct-axis demagnetization current can weaken the magnetic field and extend the motor's constant-power operating range.

[0003] For the permanent magnet synchronous motor speed control system, when the motor terminal voltage and current reach the maximum value, the current is all the direct axis current component, and the influence of the stator resistance is ignored, the ideal maximum speed n of the motor can be obtained when the ordinary field weakening control strategy is adopted. max for:

[0004]

[0005] Among them, u lim is the limit voltage, i lim is the limiting current, L d is the direct-axis synchronous inductance, ψ f is the permanent magnet flux linkage of the motor when it is not loaded, and p is the number of motor pole pairs.

[0006] Synchronous motor electromagnetic torque T e The expression is:

[0007] T e =p[ψ d i d -ψ q i q ] (2)

[0008] Among them, ψ d is the magnetic flux of the direct-axis permanent magnet, i d and i q are the direct-axis and quadrature-axis currents respectively.

[0009] For the traditional permanent magnet synchronous motor with embedded permanent magnet rotor structure, since the permanent magnet is located on the rotor direct axis, the following are true:

[0010]

[0011] Among them, L q is the quadrature-axis synchronous inductance, ψ q is the magnetic flux linkage of the quadrature-axis permanent magnet.

[0012] Substituting formula (3) into formula (2) yields:

[0013] T e =p[ψ f i q +(L d -L q )i d i q ] (4)

[0014] From formula (1), it can be seen that when the motor's limit voltage and limit current are constant, the ideal maximum speed of the motor mainly depends on the motor's no-load permanent magnet flux ψ f and direct-axis synchronous inductor L d , and the quadrature-axis synchronous inductor L q Nothing to do. f The smaller the speed, the wider the motor's magnetic field weakening speed range, but ψ f The smaller it is, the smaller the electromagnetic torque T e Therefore, unless the reluctance torque is increased, the permanent magnet synchronous motor cannot have a good performance. Although increasing the saliency ratio can effectively increase the reluctance torque, considering the magnetic saturation of the core, L q will be limited, so it is usually required to reduce L d To increase the reluctance torque. However, the traditional embedded permanent magnet rotor structure, such as Figure 3 As shown. Permanent magnet synchronous motor ψ f Big, and L d is smaller, so it is necessary to greatly increase i d To broaden the constant power speed regulation range of the motor, this will increase the capacity of the inverter, reduce the efficiency and power factor of the drive system, and at the same time, increase the risk of damage to the inverter caused by excessive back electromotive force due to weak magnetic runaway. At the same time, due to the negative direct axis current i d The generated direct-axis armature reaction flux has the opposite polarity to the permanent magnets, creating a risk of irreversible demagnetization of the permanent magnets. Therefore, the above analysis shows that for conventional permanent magnet synchronous motors with embedded permanent magnet rotors, increasing output torque (power) and expanding the constant power speed regulation range are mutually exclusive. Summary of the Invention

[0015] The present invention aims to solve the problem that the traditional permanent magnet synchronous motor with an embedded permanent magnet rotor structure cannot simultaneously increase the output torque and widen the constant power speed regulation range. A radial magnetic field reverse salient pole permanent magnet synchronous motor system is now provided.

[0016] A radial magnetic field reverse salient pole permanent magnet synchronous motor system includes a double-winding radial magnetic field reverse salient pole permanent magnet synchronous motor and an excitation power converter. The double-winding radial magnetic field reverse salient pole permanent magnet synchronous motor includes a coaxially nested stator and a rotor, with an air gap between the stator and the rotor.

[0017] The stator includes a stator core, a power winding, and a magnetic field control winding. The circumferential surface of the stator core is evenly provided with multiple axial slots. The power winding and the magnetic field control winding are both multi-phase symmetrical windings and are embedded in the multiple axial slots. The lead wires of the power winding are used to connect to the AC power supply, and the lead wires of the magnetic field control winding are connected to the AC output terminal of the excitation power converter. The AC input terminal of the excitation power converter is used to connect to the AC power supply.

[0018] The rotor includes a rotor core and a permanent magnet. The rotor core is provided with 2P first through-hole groups and 2P second through-hole groups. The 2P first through-hole groups and the 2P second through-hole groups are alternately and evenly arranged along the circumference of the rotor core. The first through-hole group is close to the outer surface of the rotor core, and the second through-hole group is close to the main axis of the rotor core.

[0019] Each first through-hole group includes n first through-holes extending axially, the cross-section of the first through-holes being a bar with both ends bent toward the surface of the rotor core, the n first through-holes being arranged radially, and the central axes of the cross-sections of the n first through-holes being the n quadrature axes of the motor respectively.

[0020] Each second through-hole group includes j second through-holes extending axially, the cross-section of the second through-holes is bar-shaped, the j second through-holes are arranged circumferentially, and the j second through-holes form a radially symmetrical structure with a direct axis of the rotor core as the symmetry axis.

[0021] Each second through hole is embedded with a permanent magnet. The permanent magnets are magnetized in parallel, and the magnetization direction is perpendicular to the length direction of the second through hole. The length direction is the length direction of the cross section of the second through hole. The magnetization directions of the permanent magnets under the same pole are the same, and the magnetization directions of the permanent magnets of adjacent poles are opposite.

[0022] P is the number of pole pairs of the motor, n and j are both positive integers, and j ≥ 2;

[0023] The direction of the magnetic lines of force generated by the direct-axis current of the magnetic field control winding is the same as that of the magnetic lines of force generated by the permanent magnet, and the direct-axis synchronous inductance is greater than the quadrature-axis synchronous inductance;

[0024] When the motor runs below the base speed, the excitation power converter outputs AC current to the magnetic field control winding, so that the direct-axis component of the magnetic field control winding current is greater than zero and remains unchanged. When the motor runs above the base speed, the direct-axis component of the magnetic field control winding current is greater than zero and decreases as the motor speed increases.

[0025] Furthermore, the lead wires of the power winding are electrically connected to the three-phase power grid through a switch, or the lead wires of the power winding are used to be electrically connected to a DC power supply through an inverter or a rectifier.

[0026] Furthermore, a reactor is connected in series between the lead wire of the magnetic field control winding and the AC output terminal of the excitation power converter, and a multi-phase capacitor group is connected in parallel to the lead wire of the magnetic field control winding.

[0027] Furthermore, the magnetization thickness of the permanent magnet is greater than or equal to 0 mm.

[0028] Furthermore, the cross section of the first through hole is arc-shaped, or is formed by connecting multiple sections of rectangular frames or trapezoidal frames end to end.

[0029] Furthermore, the radial thickness of the rotor core on both sides of the first through hole is greater than 1 mm.

[0030] Furthermore, a radial distance h from both ends of the cross section of the first through hole to the surface of the rotor core satisfies: 1 mm ≤ h ≤ 5 mm.

[0031] Furthermore, the width of the magnetic bridge between two adjacent second through holes in each pole is greater than or equal to 1 mm.

[0032] Furthermore, the above-mentioned double-winding radial magnetic field reverse salient pole permanent magnet synchronous motor includes a stator and a rotor, the stator is located outside the rotor, and the axial slots are located on the inner circumferential surface of the stator, or the rotor is located outside the stator, and the axial slots are located on the outer circumferential surface of the stator;

[0033] Alternatively, the double-winding radial magnetic field reverse salient pole permanent magnet synchronous motor includes an outer stator, a rotor and an inner stator, the rotor is located between the outer stator and the inner stator, and the axial slots are located on the inner circumferential surface of the outer stator and the outer circumferential surface of the inner stator.

[0034] Furthermore, the power winding and magnetic field control winding are integer slot windings or fractional slot windings.

[0035] The present invention changes the traditional rotor structure of the embedded permanent magnet permanent magnet synchronous motor. The permanent magnet is set at the direct axis position of the motor rotor, the magnetic conductor made of high magnetic permeability material is set at the direct axis position, and the magnetic barrier is set at the quadrature axis position. This can reduce the quadrature axis synchronous inductance L q , increase the direct-axis synchronous inductance L d , so that L d >L q , and make the direction of the direct-axis armature reaction magnetic field the same as the direction of the magnetic field generated by the permanent magnet.

[0036] Maintain the direct axis current i during motor operation d >0, the direct axis current i dThere are two functions: one is to generate direct axis magnetic flux ψ d , thereby generating reluctance torque; the second is to control the permanent magnet flux ψ f , so that the permanent magnet flux ψ f With direct axis current i d increases with the increase of the direct axis current i d It can be seen from equations (4) and (1) that this can not only improve the electromagnetic torque of the motor, but also widen the constant power speed regulation range of the motor. At this time, the direct axis current i d As the excitation current, when running above the base speed, the direct axis current i gradually decreases as the speed increases. d , thus achieving weak magnetic control similar to that of a DC motor.

[0037] The radial magnetic field reverse salient pole permanent magnet synchronous motor system of the present invention has a wide constant power operating speed range, uses a small amount of rotor permanent magnets, has high structural strength, high efficiency, and strong short-circuit fault tolerance, which makes the present invention have good application prospects in electric vehicle drive systems, electric spindle systems, flywheel energy storage systems and variable speed starting and power generation systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of the radial magnetic field reverse salient pole permanent magnet synchronous motor system according to the present invention;

[0039] Figure 2 Schematic diagram of the end face structure of the radial magnetic field reverse salient pole permanent magnet synchronous motor according to the present invention, wherein (a) is the nested structure of the stator and rotor, and (b) is the rotor;

[0040] Figure 3 This is a structural diagram of a multi-phase capacitor group connected in parallel to the lead wires of the magnetic field control winding;

[0041] Figure 4 Schematic diagram of the rotor end face structure of a traditional radial magnetic field permanent magnet synchronous motor. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] Reference Figure 1 and Figure 2 Specifically describe this embodiment, the radial magnetic field reverse salient pole permanent magnet synchronous motor system described in this embodiment is as follows Figure 1As shown, it includes a double-winding radial magnetic field anti-salient pole permanent magnet synchronous motor and an excitation power converter. The double-winding radial magnetic field anti-salient pole permanent magnet synchronous motor includes a coaxially nested stator and rotor, with an air gap between the stator and the rotor.

[0044] The stator consists of a stator core, power windings, and a field control winding. Multiple axial slots are evenly distributed around the circumference of the stator core. Both the power windings and the field control windings are multi-phase symmetrical windings embedded in the multiple axial slots. The power winding leads are electrically connected to the three-phase grid via a switch; alternatively, they are used to connect to a DC power supply via an inverter or rectifier. The field control winding leads are connected to the AC output of the excitation power converter, while the AC input of the excitation power converter is connected to the three-phase grid.

[0045] like Figure 2 As shown, the rotor includes a rotor core and permanent magnets. The rotor core is provided with four first through hole groups and four second through hole groups. The four first through hole groups and the four second through hole groups are alternately arranged evenly along the circumference of the rotor core. The first through hole group is close to the outer surface of the rotor core, and the second through hole group is close to the main axis of the rotor core.

[0046] Each first through-hole group includes two axially extending first through-holes. The cross-section of these first through-holes is a bar-shaped structure with both ends curving toward the rotor core surface. The two first through-holes are arranged radially, with the central axes of their cross-sections corresponding to the two quadrature axes of the motor. The two first through-holes are aligned parallel to each other to maximize the difference in magnetic resistance between the quadrature and axial magnetic circuits.

[0047] Each second through hole group includes two second through holes that pass through in the axial direction. The cross section of the second through holes is bar-shaped. The two second through holes are arranged in the circumferential direction. The two second through holes form a radially symmetrical structure with a direct axis of the rotor core as the symmetry axis.

[0048] A permanent magnet is embedded in each second through hole. The permanent magnets are magnetized in parallel, and the magnetization direction is perpendicular to the length direction of the second through hole. The length direction is the length direction of the cross section of the second through hole. The magnetization directions of the permanent magnets under the same pole are the same, and the magnetization directions of the permanent magnets at adjacent poles are opposite.

[0049] The direction of the magnetic lines of force generated by the direct-axis current of the magnetic field control winding is the same as the direction of the magnetic lines of force generated by the permanent magnet, and the direct-axis synchronous inductance is greater than the quadrature-axis synchronous inductance.

[0050] When the motor runs below the base speed, the excitation power converter outputs AC current to the magnetic field control winding, so that the direct-axis component of the magnetic field control winding current is greater than zero and remains unchanged. When the motor runs above the base speed, the direct-axis component of the magnetic field control winding current is greater than zero and decreases as the motor speed increases.

[0051] This embodiment uses the direct axis current i d Control permanent magnet flux ψ f , the motor has low no-load loss and high efficiency. A permanent magnet is set at the rotor direct axis and a magnetic barrier is set at the quadrature axis. The direct axis synchronous inductance L of the motor is d The motor has a wide constant power speed regulation range, small no-load back EMF, strong short-circuit fault tolerance, and high reliability and safety.

[0052] Furthermore, in practical applications, this embodiment also has the following structures that can be flexibly changed or optimized:

[0053] A reactor is connected in series between the lead wire of the magnetic field control winding and the AC output terminal of the excitation power converter, and a multi-phase capacitor group is connected in parallel to the lead wire of the magnetic field control winding to reduce the capacity of the excitation power converter, such as Figure 4 shown.

[0054] The magnetization thickness of the permanent magnet is greater than or equal to 0 mm.

[0055] The cross section of the first through hole is arc-shaped, or is formed by connecting multiple sections of rectangular frames or trapezoidal frames end to end.

[0056] The radial thickness of the rotor core on both sides of the first through hole is greater than 1 mm.

[0057] A radial distance h from both ends of the cross section of the first through hole to the surface of the rotor core satisfies: 1 mm ≤ h ≤ 5 mm.

[0058] The width of the magnetic bridge between two adjacent second through holes in each pole is greater than or equal to 1 mm.

[0059] The double-winding radial magnetic field reverse salient pole permanent magnet synchronous motor comprises a stator and a rotor, wherein the stator is located outside the rotor and the axial slots are located on the inner circumference of the stator, or the rotor is located outside the stator and the axial slots are located on the outer circumference of the stator;

[0060] Alternatively, the double-winding radial magnetic field reverse salient pole permanent magnet synchronous motor includes an outer stator, a rotor and an inner stator, the rotor is located between the outer stator and the inner stator, and the axial slots are located on the inner circumferential surface of the outer stator and the outer circumferential surface of the inner stator.

[0061] The power winding and the field control winding are integer slot windings or fractional slot windings.

[0062] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. A radial magnetic field reverse salient pole permanent magnet synchronous motor system, comprising a dual-winding radial magnetic field reverse salient pole permanent magnet synchronous motor and an excitation power converter. The dual-winding radial magnetic field reverse salient pole permanent magnet synchronous motor comprises a coaxially nested stator and rotor, with an air gap between the stator and rotor. It is characterized by: The stator includes a stator core, a power winding, and a magnetic field control winding. The circumferential surface of the stator core is evenly provided with a plurality of axial slots. The power winding and the magnetic field control winding are both multi-phase symmetrical windings and are embedded in the plurality of axial slots. The lead wires of the power winding are used to connect to an AC power supply. The lead wires of the magnetic field control winding are connected to the AC output terminal of the excitation power converter. The AC input terminal of the excitation power converter is used to connect to an AC power supply. The rotor includes a rotor core and a permanent magnet. The rotor core is provided with 2P first through-hole groups and 2P second through-hole groups. The 2P first through-hole groups and the 2P second through-hole groups are alternately and evenly arranged along the circumference of the rotor core. The first through-hole group is close to the outer surface of the rotor core, and the second through-hole group is close to the main axis of the rotor core. Each first through-hole group includes n first through-holes extending axially, wherein the cross-section of the first through-hole is a bar-shaped one with both ends bent toward the surface of the rotor core, the n first through-holes are arranged radially, and the central axes of the cross-sections of the n first through-holes are respectively the n cross axes of the motor. Each second through-hole group includes j second through-holes extending axially, wherein the cross-section of the second through-hole is bar-shaped, the j second through-holes are arranged circumferentially, and the j second through-holes form a radially symmetrical structure with a direct axis of the rotor core as a symmetry axis. Each second through hole is embedded with a permanent magnet. The permanent magnets are magnetized in parallel, and the magnetization direction is perpendicular to the length direction of the second through hole. The length direction is the length direction of the cross section of the second through hole. The magnetization directions of the permanent magnets under the same pole are the same, and the magnetization directions of the permanent magnets of adjacent poles are opposite. P is the number of pole pairs of the motor, n and j are both positive integers, and j ≥ 2; The direction of the magnetic lines of force generated by the direct-axis current of the magnetic field control winding is the same as the direction of the magnetic lines of force generated by the permanent magnet, and the direct-axis synchronous inductance is greater than the quadrature-axis synchronous inductance; When the motor runs below the base speed, the excitation power converter outputs AC current to the magnetic field control winding, so that the direct-axis component of the magnetic field control winding current is greater than zero and remains unchanged. When the motor runs above the base speed, the direct-axis component of the magnetic field control winding current is greater than zero and decreases as the motor speed increases.

2. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1, characterized in that: The lead wires of the power winding are electrically connected to the three-phase power grid through a switch. Alternatively, the lead wires of the power winding are used to be electrically connected to a DC power supply through an inverter or a rectifier.

3. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1 or 2, characterized in that: A reactor is connected in series between the lead wire of the magnetic field control winding and the AC output terminal of the excitation power converter, and a multi-phase capacitor group is connected in parallel to the lead wire of the magnetic field control winding.

4. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1, characterized in that: The magnetization thickness of the permanent magnet is greater than or equal to 0 mm.

5. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1, characterized in that: The cross section of the first through hole is arc-shaped, or is formed by connecting multiple sections of rectangular frames or trapezoidal frames end to end.

6. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1, characterized in that: The radial thickness of the rotor core on both sides of the first through hole is greater than 1 mm.

7. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1, 5 or 6, characterized in that: A radial distance h from both ends of the cross section of the first through hole to the surface of the rotor core satisfies: 1 mm ≤ h ≤ 5 mm.

8. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1, characterized in that: The width of the magnetic bridge between two adjacent second through holes in each pole is greater than or equal to 1 mm.

9. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1, characterized in that: The double-winding radial magnetic field reverse salient pole permanent magnet synchronous motor includes a stator and a rotor, wherein the stator is located outside the rotor, and the axial slots are located on the inner circumferential surface of the stator, or the rotor is located outside the stator, and the axial slots are located on the outer circumferential surface of the stator; Alternatively, the dual-winding radial magnetic field reverse salient pole permanent magnet synchronous motor includes an outer stator, a rotor and an inner stator, the rotor is located between the outer stator and the inner stator, and the axial slots are located on the inner circumferential surface of the outer stator and the outer circumferential surface of the inner stator.

10. The radial magnetic field reverse salient pole permanent magnet synchronous motor system according to claim 1, characterized in that: The power winding and the field control winding are integer slot windings or fractional slot windings.

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