A natural electromagnetic levitation three-phase permanent magnet motor

Abstract

A natural electromagnetic levitation three-phase permanent magnet motor is disclosed, relating to the field of motors. This invention aims to solve the problem of the large size and difficulty in controlling the magnetic levitation bearings in magnetic levitation motors. The natural electromagnetic levitation three-phase permanent magnet motor of this invention has a stator core and surface-mounted permanent magnets, both divided into n segments along the axial direction, where n is a positive integer greater than or equal to 3. When the ratio of the number of stator slots Z on the stator core to the number of phases m of the stator winding is odd, the number of poles P and Zm have a common divisor. Each phase stator winding includes K pairs of parallel branches, 1≤K≤Z2m, and the two parallel branches are centrally symmetrically arranged with the motor center as the center of symmetry. When the number of pole pairs P is even, the opposite ends of the two branches are connected; when the number of pole pairs P is even, the same ends of the two branches are connected.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electric machines, and particularly relates to electric machine windings. BACKGROUND

[0002] Electric machines are the most common and most frequently used electrical equipment. For example, energy storage flywheels, maglev trains, all-electric aircraft turbine engines, ship hydrodynamic propellers, ultra-low noise submarine drives, oceanic tidal power generation, nuclear power, space and super-high-speed applications all have electric machines. Bearings are present in conventional electric machines, and it is desirable for the friction to be as small as possible, at which point magnetic suspension becomes a necessary technology. In a conventional magnetic suspension electric machine, the volume of the magnetic suspension bearing accounts for 60%, and the controller of the magnetic suspension bearing is high in cost and complex, so it is a difficult problem to make the electric machine rotor levitate. SUMMARY

[0003] The present application is to solve the problem of large volume and difficult control of the magnetic suspension bearing in the magnetic suspension electric machine, and provides a natural electromagnetic magnetic suspension three-phase permanent magnet electric machine.

[0004] A natural electromagnetic magnetic suspension three-phase permanent magnet electric machine, comprising: a rotor and a stator coaxially nested from inside to outside, the stator comprising a stator core and a stator winding, the rotor comprising a rotor core and a surface-mounted permanent magnet, the stator core and the surface-mounted permanent magnet are each divided into n segments along the axial direction, n being a positive integer greater than or equal to 3; when the ratio of the number of stator slots Z on the stator core to the number of phases m of the stator winding is odd, the number of poles P of the electric machine and Zm have a common divisor; each phase of the stator winding comprises K pairs of parallel branches, 1≤K≤Z2m, and the two parallel branches are symmetrically arranged with the center of the electric machine as the center of symmetry, when the number of pole pairs P of the electric machine is even, the two branches are connected at the different name ends, and when the number of pole pairs P of the electric machine is even, the two branches are connected at the same name end.

[0005] Further, the stator gap λ d between the two axially adjacent stator core segments is equal to the rotor gap λ r between the two axially adjacent surface-mounted permanent magnet segments, and λ d = λ r = δ~2δ, δ being the electromagnetic air gap.

[0006] Alternatively, the stator gap λ d between the two axially adjacent stator core segments is equal to the gap λ r0 between the two adjacent non-end surface-mounted permanent magnet segments, and λ d = λ r0 = δ~2δ, δ being the electromagnetic air gap; the gap λ rd between the permanent magnet segment at the end and its adjacent permanent magnet segment is greater than λ r0 , and λ rd = 1.5 λ r0~2λ r0 .

[0007] Further, the natural electromagnetic magnetic suspension three-phase permanent magnet motor has a shell, and the rotor and the stator are located inside the shell.

[0008] Further, one end of each branch is used as a midpoint of the phase winding.

[0009] Further, the same-name ends of the windings in the adjacent two slots of each phase stator winding are connected in series to form a branch.

[0010] The application only needs to adopt a suitable pole-slot matching, and without adding any sensors and controllers, the radial natural dynamic electromagnetic magnetic suspension and the axial passive magnetic suspension can be realized by combining the motor winding in series and parallel and matching the core segmentation. The application can unload the self-weight of any bearing motor, prolong the bearing life, reduce the noise, reduce the motor loss and save energy. The natural electromagnetic magnetic suspension can make the motor rotor rotate in a state that the energy loss tends to be minimum, and at this time, the vibration and noise are minimum. It is especially suitable for wind turbines, steam turbines, water turbines, compressor motors, dust collectors, high-speed grinders and the like. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is a schematic diagram of a traditional 14-pole 12-slot motor structure, wherein each phase has one branch;

[0012] Figure 2 It is a schematic diagram of the axial section of the natural electromagnetic magnetic suspension three-phase permanent magnet motor;

[0013] Figure 3 It is a schematic diagram of a 10-pole 12-slot natural magnetic suspension motor, wherein each phase has a pair of parallel branches;

[0014] Figure 4 It is a schematic diagram of a 14-pole 12-slot natural magnetic suspension motor, wherein each phase has a pair of parallel branches;

[0015] Figure 5 It is a schematic diagram of a 10-pole 12-slot natural magnetic suspension motor, wherein each phase has a pair of short-circuit windings;

[0016] Figure 6 It is a schematic diagram of a 10-pole 12-slot natural magnetic suspension motor, wherein each phase has two pairs of parallel branches;

[0017] Figure 7 It is a schematic diagram of a 10-pole 12-slot natural magnetic suspension motor, wherein each phase has a pair of parallel branches and a pair of short-circuit windings. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0019] In a conventional motor, when the ratio of the number of stator poles Z (the number of teeth and slots) to the number of phases m is even, usually there is only one branch per phase, for example, as shown in the figure, a three-phase symmetrical 14-pole 12-slot motor has one branch per phase. If the air gap of the motor is eccentric, it will cause the three-phase current to be asymmetric, and will lead to motor eccentric vibration and noise, and the conventional motor cannot generate magnetic suspension restoring force. Therefore, the present application provides the following implementation.

[0020] Specific implementation one: a natural electromagnetic magnetic suspension three-phase permanent magnet motor, comprising: a rotor, a stator and an outer shell 7 coaxially nested from inside to outside, the stator comprises a stator core 1 and a stator winding 5, and the rotor comprises a rotor core 2 and a surface-mounted permanent magnet 3.

[0021] The stator core 1 and the surface-mounted permanent magnet 3 are both divided into n=5 segments along the axial direction. The stator gap 6λ d between the two axially adjacent stator core segments is equal to the gap λ r0 between the two adjacent non-end surface-mounted permanent magnet segments, and has λ d =λ r0 =δ~2δ, δ is the electromagnetic air gap. The gap λ rd between the permanent magnet segment at the end and its adjacent permanent magnet segment has λ r0 >λ rd , and has λ r0 =1.5λ r0 ~2λ jx . After segmentation, the maximum stiffness of the axial passive magnetic suspension is approximately 0.95nK (Nmmm), where K (Nmmm) is the stiffness of the single segment axial passive magnetic suspension.

[0022] The ratio of the number of stator slots Z on the stator core 1 to the number of phases m of the stator winding 5 is even, so that the winding of each phase of the motor can form a centrally symmetric distribution of the winding, and a centrally symmetric couple torque can be generated. When Zm is odd, it is not conducive to become a motor with natural electromagnetic magnetic suspension. Therefore, when the ratio of the number of stator slots Z on the stator core 1 to the number of phases m of the stator winding 5 is odd, the motor pole number P and Zm have a common divisor. For example, P=3, Zm=3, the common divisor is 3; P=15, Zm=9, the common divisor is 3; P=10, Zm=5, the common divisor is 5.

[0023] Each phase stator winding 5 includes K pairs of parallel branch circuits, 1≤K≤Z / 2m. Each phase adjacent winding end-to-end is connected in series to form a branch circuit, and then the adjacent winding end-to-end is connected in series to form another branch circuit, and then the two symmetrical branch circuits are connected to form a parallel branch circuit winding. One end of the two branch circuits serves as the midpoint of the phase winding. The two parallel branch circuits are symmetrically arranged with the motor center as the center of symmetry. When the motor pole pair number P is even, the two branch circuits are connected in parallel at the different name ends; when the motor pole pair number P is even, the two branch circuits are connected in parallel at the same name end. The motor becomes a motor with natural electromagnetic magnetic suspension restoring force. The three-phase winding of the motor is formed by the above method to form a 180° symmetrical parallel branch circuit, so that three-phase ports and a three-phase winding midpoint of the three-phase winding are generated. That is, a special 180° symmetrical parallel parallel branch circuit three-phase winding is finally formed. The more the parallel branch circuits, the more the slot turns, and the greater the restoring force. The natural electromagnetic magnetic suspension restoring force is proportional to the square of the increase multiple of the parallel branch circuits.

[0024] Due to the attraction between the stator core 1 and the surface-mounted permanent magnet 3, the air gap between the stator and the rotor is kept equal under the action of the bearing. The attraction is equal everywhere along the circumference, and the bearing makes the radial attraction force in the motor air gap equal everywhere and mutually offset. However, if the motor rotates, the bearing fails, and the motor has a deviation in the air gap of the same diameter, the permanent magnet rotor body will be attracted to the side with smaller air gap, and the counter electromotive force of the parallel branch circuit on the side with smaller air gap will become larger, and the current will become smaller. Conversely, the counter electromotive force of the parallel branch circuit on the side with larger air gap will become smaller, and the current will become larger. Therefore, the radial force on the side with larger air gap becomes larger, and the radial force on the side with smaller air gap becomes smaller, which inevitably leads to the change of the air gap in the direction of smaller deviation, and makes the air gap deviation stable. Therefore, after the motor rotates, the present embodiment has the ability to restore the radial natural magnetic suspension.

[0025] The permanent magnet is the main body of the motor to generate driving torque, but the permanent magnet will also generate an uncontrollable radial magnetic pull force jx . This force will pull the motor in any direction where the air gap is zero. Therefore, the magnetic suspension force f je generated by the radial natural electromagnetic active magnetic suspension must be greater than f jx , so as to ensure that the synthesized radial magnetic suspension force f j can produce stable radial magnetic suspension effect.

[0026] The radial magnetic pull force f jx generated by the permanent magnet is δ A2μ0, where μ0 is the air gap permeability, A is the air gap surface area per pole, and B δ is the air gap magnetic flux density. The larger the electromagnetic air gap, the smaller the air gap magnetic flux density B δ . When the electromagnetic air gap becomes larger, the air gap magnetic flux density B δwill be smaller. When the electromagnetic air gap is small, the change relation is linear, and when the electromagnetic air gap is large, the change relation is a power function. The magnetic suspension force generated by the natural electromagnetic active magnetic suspension is proportional to the square of the current deviation of the parallel branch or the square of the back electromotive force deviation, and is proportional to the square of the number of turns of the winding. The stable magnetic suspension condition of the radial natural electromagnetic magnetic suspension is: f je > f jx Since the radial natural electromagnetic magnetic suspension force is zero when the motor speed is zero, the motor rotor will be attracted to any position where the mechanical air gap is zero. The present technology cannot provide static radial electromagnetic magnetic suspension. Generally, the mechanical air gap δ j of the motor is smaller than the electromagnetic air gap, that is, the air gap change range of the motor during operation is only ± δ j , and at this time the radial magnetic pull f jx generated by the permanent magnet is relatively small. The larger the diameter of the motor, the smaller the radial magnetic pull due to the relatively small air gap, and the larger the natural electromagnetic magnetic suspension force, which is more suitable for large motors.

[0027] Since the permanent magnet rotor body will be randomly attracted to the side with a small air gap when the motor is not started, the permanent magnet rotor body is not stable in the radial direction. Therefore, a protective bearing can also be used in actual applications. Thus, the present embodiment has perfect dynamic radial natural electromagnetic magnetic suspension and passive axial magnetic suspension functions using a conventional motor driving method without adding any sensors and controllers.

[0028] As shown in FIGS. Figure 5 and 7 , in order to increase the natural magnetic suspension restoring force, short-circuit windings dedicated to improving the natural magnetic suspension restoring force can also be added on each adjacent slot of each phase. Based on the same principle, there is an attractive force between the stator core 1 and the surface-mounted permanent magnet 3, and the bearing keeps the air gap between the stator and the rotor equal due to the action of the bearing. The attractive force is equal everywhere along the circumference, and the bearing makes the radial attractive force in the motor air gap equal everywhere and mutually offset. However, if the motor rotates and the bearing fails, the air gaps on both sides of 180° will inevitably be different. At this time, the permanent magnet rotor body will be attracted to the side with a small air gap, and the back electromotive force deviation of the parallel short-circuit winding branch on the side with a small air gap will inevitably become larger, and the current will become smaller; on the contrary, the back electromotive force of the parallel short-circuit winding branch on the side with a large air gap will become smaller, and the current will become larger, so that the radial pull on the side with a large air gap becomes larger, and the radial pull on the side with a small air gap becomes smaller, which inevitably leads to a change in the air gap in the direction of the smaller deviation, and stabilizes the air gap deviation. Since the size of the radial natural magnetic suspension restoring force is proportional to the square of the back electromotive force deviation, the method of adding a dedicated radial natural magnetic suspension winding can be used when needed.

[0029] For the motor with output shaft, in order to improve the change of load on the output shaft, still increase the auxiliary bearing, the size of the auxiliary bearing can be smaller than the size of the traditional bearing, so as to reduce the bearing friction: the outer circle of the auxiliary bearing can be covered with elastic rubber ring, so as to provide mechanical buffer, reduce the vibration and noise of the motor; The bearing gap of the auxiliary bearing can be increased from negative gap to 0.1-1mm; The natural electromagnetic magnetic suspension restoring force keeps the shaft center of the motor output shaft stable. At this time, although there is an auxiliary bearing, the natural electromagnetic magnetic suspension can still make the motor rotor rotate in a state of minimum energy loss, at this time the vibration and noise are minimum, just like the earth and the sun naturally rotate in the space.

[0030] While the application has been described with reference to particular embodiments thereof, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present application. It will thus be appreciated that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the present application as defined by the appended claims. It will be understood that the features described with respect to one embodiment can be used in other embodiments.

Claims

1. A natural electromagnetic maglev three-phase permanent magnet electric machine comprising: A rotor and a stator coaxially nested from inside to outside, the stator comprising a stator core (1) and a stator winding (5), the rotor comprising a rotor core (2) and surface-mounted permanent magnets (3), Characterized in that the stator core (1) and the surface-mounted permanent magnet (3) are all divided into segments along the axial direction, is a positive integer greater than or equal to 3; When the ratio of the number of stator slots (2) on the stator core (1) to the number of phases of the stator winding (5) is odd, the number of poles of the motor and has a common divisor and ​ Each phase stator winding (5) comprises The two branches are in parallel connection with each other. The two branches are in parallel connection with each other, and the two branches are symmetrically arranged with the center of the motor as the symmetric center. When the number of pole pairs of the motor is even, the two branches are connected at the different name terminals. When the number of pole pairs of the motor is odd, the two branches are connected at the same name terminals.

2. A natural electromagnetic maglev three-phase permanent magnet motor according to claim 1, characterized in that, Stator gap (6) between two axially adjacent stator core segments (1) Rotor gap (4) between two axially adjacent surface-mounted permanent magnets (3) are equal and have , are electromagnetic air gaps.

3. A natural electromagnetic maglev three-phase permanent magnet motor according to claim 1, characterized in that, The length of the stator gap (6) between two axially adjacent stator cores (1) The length of the gap between two adjacent non-end surface-mounted permanent magnets (3) Equal, and have , Electromagnetic air gap A gap between an end located permanent magnet segment and its adjacent permanent magnet segment , and .

4. A natural electromagnetic maglev three-phase permanent magnet motor according to claim 1, 2 or 3, characterized in that, Further comprising a housing (7), the rotor and the stator are located inside the housing (7).

5. A natural electromagnetic maglev three-phase permanent magnet motor according to claim 4, characterized in that, One end of the two branches serves as the midpoint of the phase winding.

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