CN109698600B - Linear motor with auxiliary weak magnetic structure - Google Patents

Linear motor with auxiliary weak magnetic structure Download PDF

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Publication number
CN109698600B
CN109698600B CN201811505907.8A CN201811505907A CN109698600B CN 109698600 B CN109698600 B CN 109698600B CN 201811505907 A CN201811505907 A CN 201811505907A CN 109698600 B CN109698600 B CN 109698600B
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magnetic
armature winding
linear motor
pole
auxiliary
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CN109698600A (en
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张瑞华
赵牧天
张丽
杜玉梅
史黎明
葛琼璇
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Institute of Electrical Engineering of CAS
CRRC Tangshan Co Ltd
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Institute of Electrical Engineering of CAS
CRRC Tangshan Co Ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02KDYNAMO-ELECTRIC MACHINES
    • H02K41/00Propulsion systems in which a rigid body is moved along a path due to dynamo-electric interaction between the body and a magnetic field travelling along the path
    • H02K41/02Linear motors; Sectional motors
    • H02K41/03Synchronous motors; Motors moving step by step; Reluctance motors
    • H02K41/031Synchronous motors; Motors moving step by step; Reluctance motors of the permanent magnet type

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  • Physics & Mathematics (AREA)
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Abstract

The invention provides a linear motor with an auxiliary weak magnetic structure, which comprises a secondary magnetic pole, a magnetic part, a primary tooth space and an armature winding, wherein the armature winding is fixed on the primary tooth space, the secondary magnetic pole is arranged on one side or two sides of the armature winding, the first side of the secondary magnetic pole is close to the armature winding, an air gap is formed between the first side and the armature winding, the surface of the second side of the secondary magnetic pole is provided with the magnetic part, and the magnetic part is the auxiliary weak magnetic part. By implementing the invention, the magnetic part is arranged on the surface of one side of the secondary magnetic pole opposite to the air gap side, the magnetic part provides a low-reluctance magnetic circuit for the magnetic field generated by the permanent magnet magnetic field and the armature current, so that more magnetic leakage chains on the back side of the permanent magnet are closed in the magnetic part, the proportion of demagnetizing flux in the effective part of the air gap is larger, the low-reluctance magnetic circuit increases the direct-axis inductance of the armature winding, the armature reaction effect is enhanced, the field weakening difficulty of the linear motor is reduced, and the field weakening performance is good.

Description

Linear motor with auxiliary weak magnetic structure
Technical Field
The invention relates to the technical field of motors, in particular to a linear motor with an auxiliary flux weakening structure.
Background
With the advance of advanced rail transit key specials in national key research and development plans and the acceleration of urbanization progress in China, rail transit systems driven by linear motors are developed rapidly, and the rail transit systems mainly comprise high-speed magnetic levitation, medium-low speed magnetic levitation, subways drawn by linear motors and the like. The linear motor can be divided into a linear asynchronous motor and a linear synchronous motor according to types, wherein secondary excitation of the linear synchronous motor can be electric excitation or permanent magnet excitation, and a magnetic field can be established in an air gap by permanent magnet excitation without additional energy, i.e. additional windings and a direct-current power supply are not needed, so that the structure of the motor can be simplified, and energy can be saved. In order to save cost and facilitate maintenance, the permanent magnet secondary is required to be made into a short secondary and installed at the bottom of the carriage, namely, a scheme of a long primary permanent magnet linear synchronous motor is adopted.
The operation of the permanent magnet linear synchronous motor is controlled by a traction substation, and an inverter in the traction substation changes the operation speed of the motor through variable frequency speed regulation. Because the maximum speed of the motor is limited by the direct-current bus voltage of the inverter, the motor can not be infinitely accelerated, because the back electromotive force of the armature winding is increased along with the increase of the speed, when the back electromotive force reaches the maximum value of the output voltage of the inverter, the current regulator is saturated, the inverter can not continuously output current, and the speed can not be further increased; secondly, because the winding impedance of the uncovered area of the train magnetic pole is larger and the feed cable is longer, the voltage loss of the voltage output by the inverter in the two parts is more, and the speed of the motor is further limited to be improved; in addition, the direct-current bus voltage of the inverter cannot be infinitely increased, the stress of the overhigh direct-current bus voltage on the switch device cannot be ignored, and the difficulty in type selection of the switch device is high; for these objective reasons, it is difficult to increase the speed of the motor, and if the motor is to reach a higher speed under the limitation of the dc bus voltage of the inverter, the motor is usually accelerated by the field weakening control.
For the weak magnetic control strategy of the permanent magnet synchronous motor, at present, a table look-up method, advance angle control, a gradient descent method, a single current regulator method and the like are mainly used, but the weak magnetic control strategy is implemented on the premise that the motor is easy to weaken magnetic, as the permanent magnet linear synchronous motor cannot weaken magnetic directly compared with an electrically excited linear synchronous motor, reverse direct axis current needs to be added to offset part of permanent magnet flux linkage, but demagnetization current cannot be too large, otherwise permanent magnet demagnetization can be caused, the air gap of the motor is large, the remanence and coercive force of a permanent magnet are high, and the purpose of weakening magnetic can be achieved by using large demagnetization current, so that the weak magnetic performance of the permanent magnet linear motor is poor.
Disclosure of Invention
In view of this, the embodiment of the present invention provides a linear motor with an auxiliary flux weakening structure, so as to solve the problem that the existing permanent magnet linear synchronous motor has poor flux weakening performance.
Therefore, the embodiment of the invention provides the following technical scheme:
the embodiment of the invention provides a linear motor with an auxiliary weak magnetic structure, which comprises: the secondary magnetic pole, the magnetic part, the primary tooth space and the armature winding; the armature winding is fixed on the primary tooth groove; the secondary magnetic pole is arranged on one side or two sides of the armature winding, and an air gap is formed between the first side of the secondary magnetic pole and the armature winding; the magnetic part is arranged on the surface of a second side of the secondary magnetic pole, wherein the first side is the side, close to the armature winding, of the secondary magnetic pole, the second side is the side, far away from the armature winding, of the secondary magnetic pole, and the auxiliary weak magnetic structure is the magnetic part.
Preferably, the material of the magnetic member is a soft magnetic material.
Preferably, the magnetic member includes: silicon steel sheet, permalloy sheet, magnetic steel, and soft magnetic ferrite.
Preferably, the secondary magnetic pole comprises: a plurality of unit permanent magnets arranged according to a Halbach array.
Preferably, the plurality of magnetic members are correspondingly and adaptively covered and arranged on the surfaces of the plurality of unit permanent magnets respectively.
Preferably, a plurality of the unit permanent magnets are arranged in a close arrangement or spaced apart by a predetermined distance.
Preferably, the magnetic member is in the form of: whole block type, laminated type, and several strip type.
Preferably, the thickness of the magnetic member is a preset thickness, and the preset thickness is smaller than the thickness of the secondary magnetic pole.
Preferably, the two sides of the armature winding and the secondary pole form two air gaps with equal width.
Preferably, the primary slots are ironless primary slots.
The technical scheme of the embodiment of the invention has the following advantages:
the embodiment of the invention provides a linear motor with an auxiliary weak magnetic structure, which comprises a secondary magnetic pole, a magnetic part, a primary tooth space and an armature winding, wherein the magnetic part is the auxiliary weak magnetic structure, the armature winding is fixed on the primary tooth space, the secondary magnetic pole is arranged on one side or two sides of the armature winding, an air gap is formed between the first side of the secondary magnetic pole and the armature winding, the surface of the second side of the secondary magnetic pole is provided with the magnetic part, the first side is the side of the secondary magnetic pole close to the armature winding, and the second side is the side of the secondary magnetic pole far away from the armature winding. According to the linear motor with the auxiliary weak magnetic structure, the magnetic part is arranged on the surface of one side, opposite to the air gap side, of the secondary magnetic pole, the magnetic part provides a low-reluctance magnetic circuit for a magnetic field generated by a permanent magnet magnetic field and armature current, so that more magnetic leakage chains on the back side of the permanent magnet are closed in the magnetic part, the proportion of demagnetizing flux in the effective part of the air gap is larger, the low-reluctance magnetic circuit increases the straight-axis inductance of an armature winding, the armature reaction effect is enhanced, the weak magnetic difficulty of the linear motor is reduced, compared with the existing linear motor, the weak magnetic performance is good, the weak magnetic current required when the same weak magnetic effect is achieved is greatly reduced, and the linear motor is easy to accelerate.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a two-dimensional cross-sectional view of a linear motor having an auxiliary flux weakening structure according to an embodiment of the present invention;
FIG. 2a is a schematic view of a unit permanent magnet without an auxiliary flux weakening member in accordance with an embodiment of the present invention;
FIG. 2b is a schematic view of a unit permanent magnet with auxiliary flux weakening members according to an embodiment of the present invention;
FIG. 2c is another schematic view of a unit permanent magnet with auxiliary flux weakening members according to an embodiment of the present invention;
fig. 3 is another two-dimensional cross-sectional view of a linear motor having an auxiliary flux weakening structure according to an embodiment of the present invention;
FIG. 4a is a magnetic force line distribution diagram of the non-magnetic part on the secondary magnetic pole when the motor is in no-load operation;
FIG. 4b is a magnetic flux distribution plot for a motor with magnetic elements on the secondary pole during no-load operation;
FIG. 5a shows the straight axis (I) of a linear motor without magnetic elements on the secondary poled) Quadrature axis (I)q) A current waveform diagram;
FIG. 5b shows the straight axis (I) of a linear motor with magnetic members on the secondary poled) Quadrature axis (I)q) A current waveform diagram;
reference numerals: 1-secondary magnetic pole, 11-unit permanent magnet; 2-a magnetic member; 3-primary gullet; 4-armature winding.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example one
In the embodiment of the present invention, there is provided a linear motor with an auxiliary flux weakening structure, as shown in fig. 1, the linear motor with an auxiliary flux weakening structure includes a secondary magnetic pole 1, a magnetic member 2, a primary slot 3 and an armature winding 4, wherein the magnetic member 2 is the auxiliary flux weakening structure, the armature winding 4 is fixed on the primary slot 3, the secondary magnetic pole 1 is disposed on one side of the armature winding 4, a first side of the secondary magnetic pole 1 is close to the armature winding 4, an air gap is formed between the first side and the armature winding 4, a magnetic member 2 is disposed on a surface of a second side of the secondary magnetic pole 1, the magnetic member 2 is the auxiliary flux weakening member and can be disposed on a surface of the second side of the secondary magnetic pole 1 by a pasting manner, the second side is opposite to the air gap side, in the embodiment of the present invention, the auxiliary flux weakening member is disposed on the surface of the secondary magnetic pole 1 by a pasting manner, but can also, for example, the auxiliary flux weakening member is fixed in the sleeve together with the unit permanent magnet, and the embodiment of the invention is not limited thereto. According to the linear motor with the auxiliary flux weakening structure, the magnetic part 2 is arranged on the surface of one side, opposite to the air gap side, of the secondary magnetic pole 1, the magnetic part 2 provides a low-reluctance magnetic circuit for a permanent magnet magnetic field and a magnetic field generated by armature current, so that more flux leakage chains on the back side of the permanent magnet are closed in the magnetic part, and the proportion of the effective part of the demagnetizing flux in the air gap is larger, the low-reluctance magnetic circuit increases the direct-axis inductance of the armature winding 4, enhances the effect of armature reaction, reduces the flux weakening difficulty of the linear motor, compared with the prior linear motor, the weak magnetic performance is good, and the weak magnetic current required when the same weak magnetic effect is achieved is greatly reduced, therefore, the linear motor is easy to accelerate, and because the motor is a linear synchronous motor, the magnetic poles and the traveling wave magnetic field move synchronously, and the magnetic part 2 covered on the secondary magnetic pole 1 does not increase extra eddy current loss and hysteresis loss.
In a preferred embodiment, the magnetic member 2 of the embodiment of the present invention is a soft magnetic material with low coercivity and high permeability, specifically, a silicon steel sheet, a permalloy sheet, a magnetically conductive steel or a soft magnetic ferrite.
In order to make the magnetic field distribution uniform, in a specific embodiment, the secondary magnetic pole 1 includes eight unit permanent magnets 11 arranged in a Halbach array, and the eight unit permanent magnets 11 form a periodic array structure, that is, the magnetizing angle of each unit permanent magnet 11 changes forty-five degrees in sequence, as shown in the arrow direction in fig. 1, each unit permanent magnet 11 may be arranged closely or may be arranged at a preset distance. In the embodiment of the present invention, each unit permanent magnet 11 is spaced by a preset distance, and the magnetic members 2 are correspondingly and adaptively covered on the second side of each unit permanent magnet 11, that is, the number of the magnetic members 2 and the number of the unit permanent magnets 11 are consistent, and the magnetic members 2 are covered on the unit permanent magnets 11 with the same length and width, and the gap between two unit permanent magnets 11 does not cover the magnetic members 2. The cross-sectional height of the magnetic member 2 is a predetermined thickness, which is smaller than the thickness of the unit permanent magnet 11, and both cross-sectional shapes are rectangular. The magnetic member 2 may be made into a whole piece and adhered to the surface of the unit permanent magnet 11, or may be in a laminated type of magnetic steel, or a strip-shaped splicing type, which is not limited in the embodiments of the present invention. In the embodiment of the present invention, the auxiliary weak magnetic member is disposed on the surface of the secondary magnetic pole 1 by means of adhesion, but may also be fixed in the sleeve by other means, for example, the auxiliary weak magnetic member and the unit permanent magnet are fixed together, and the embodiment of the present invention is not limited thereto. Fig. 2a shows a unit permanent magnet having no magnetic member on the surface, fig. 2b shows a unit permanent magnet having a magnetic member formed by laminating a plurality of silicon steel sheets on the surface, the laminating direction being in the positive direction of the Z-axis, and fig. 2c shows a unit permanent magnet having a magnetic member formed by a bulk permalloy on the surface.
In order to solve the problem of normal force (attractive force or repulsive force) between the primary and secondary coils, in a specific embodiment, the primary tooth slot 3 in the embodiment of the present invention is an ironless primary tooth slot, the material of the primary tooth slot is non-magnetic and non-conductive engineering plastic, epoxy resin, ABS engineering plastic, nylon PA, etc., the number of slots per pole and phase of the primary tooth slot 3 in the embodiment of the present invention is 1, and the material of the armature winding 4 may be copper, aluminum, etc.
In one embodiment, as shown in fig. 3, the linear motor with the auxiliary flux weakening structure according to the embodiment of the present invention may further include a secondary pole 1 and a magnetic member 2 disposed on both sides of the armature winding 4, that is, when the secondary pole 1 and the magnetic member 2 are disposed on one side of the armature winding 4, a single-sided coreless permanent magnet linear synchronous motor is formed, when the secondary pole 1 and the magnetic member 2 are disposed on both sides of the armature winding 4, a double-sided coreless permanent magnet linear synchronous motor is formed, and when the double-sided coreless permanent magnet linear synchronous motor is formed, the widths of air gaps on both sides of the armature winding 4 and the primary tooth slot 3 are equal.
In order to better illustrate the field weakening effect of the linear motor with the auxiliary field weakening structure, the embodiment of the invention also provides specific simulation data, and specifically, for a single-side coreless permanent magnet linear synchronous motor, parameters such as magnetic line distribution, armature winding back electromotive force, direct axis inductance, and the magnitude of field weakening current required for reaching a given speed of the motor are compared by using finite element simulation software Maxwell and power electronic simulation software Psim to illustrate the field weakening effect of the linear motor with the auxiliary field weakening structure.
Fig. 4a is a magnetic force line distribution diagram when the motor without the magnetic member on the secondary magnetic pole operates in no-load operation, and fig. 4b is a magnetic force line distribution diagram when the motor with the magnetic member on the secondary magnetic pole operates in no-load operation. In no-load operation, the armature winding 4 has no current and no armature reaction, all air gap magnetic lines are generated by the permanent magnet, and the simulation conditions are as follows: the same running speed, primary and secondary sizes, primary and secondary materials and air gap length are adopted, and then the magnetic line distribution of the two is compared according to the simulation result. As can be seen from fig. 4b, the magnetic member 2 provides a low reluctance magnetic circuit for the magnetic field of the partial unit permanent magnet, so that the magnetic flux lines of the leakage flux on the back side (the side opposite to the air gap) of the secondary magnetic pole 1 are closed in the magnetic member 2. When the motor without the magnetic member 2 is in idle operation, as can be seen from fig. 4a, the magnetic permeability of the permanent magnet is similar to that of the vacuum, and the leakage flux is more on the back side (the side opposite to the air gap) of the secondary magnetic pole 1. The armature winding back electromotive force and the direct-axis inductance of the armature winding and the direct-axis inductance are calculated through simulation, and the result is shown in table 1:
TABLE 1 armature winding counter electromotive force and direct axis inductance
Figure BDA0001899441710000091
The simulation results in the table above show that when equal demagnetization currents are applied, the back electromotive force amplitude of the motor with the magnetic part 2 on the secondary magnetic pole 1 is lower than that of the motor without the magnetic part 2, and when the demagnetization current of 500A is applied to the motor without the magnetic part 2 on the secondary magnetic pole 1, the back electromotive force amplitude is close to that of the motor with the magnetic part 2 when the motor is in no-load operation. Therefore, compared with the coreless permanent magnet linear synchronous motor without the auxiliary weak magnetic piece, the linear motor with the magnetic piece 2 on the secondary magnetic pole 1 of the embodiment of the invention can save at least 500A of weak magnetic current under the weak magnetic control.
The auxiliary weak magnetic member in the embodiment of the invention is a silicon steel sheet, and has high magnetic conductivity, so that the inductance of the armature winding is increased, and the effect of armature reaction is enhanced. The embodiment of the invention also calculates the direct axis inductance L of the linear motor whether the secondary magnetic pole 1 is covered with the magnetic part 2, and the obtained result is the direct axis inductance L of the motor with the silicon steel sheetd1Direct-axis inductance L of motor without silicon steel sheet as 5.55 mu Hd25.39 muH, when the same flux weakening effect is required, i.e. the equal permanent magnet flux delta psi is to be cancelledfIn the embodiment of the invention, the linear motor with the auxiliary weak magnetic part can save the weak magnetic current of (delta psi)f/Ld2-Δψf/Ld1) A, for example, to offset the permanent magnet flux of 0.1Wb, the linear motor of the embodiment of the present invention can save the field weakening current 535A.
Then, Psim simulation is respectively used for the linear motor with the magnetic part 2 on the secondary magnetic pole and the linear motor without the magnetic part 2, and i is adopted below the basic speeddThe control is 0, and the weak magnetic control is adopted above the basic speed. When the motor is accelerated to a given speed of 200km/h, the straight shaft (I) of the linear motor without the magnetic part 2 on the secondary magnetic pole 1d) Quadrature axis (I)q) The current waveform is shown in FIG. 5a, the straight shaft (I) of a linear motor having a magnetic member 2 on the secondary magnetic pole 1d) Quadrature axis (I)q) The current waveform is shown in fig. 5 b. After switching to the field weakening control, the direct-axis current changes from 0 to a negative value, and the quadrature-axis current decreases because the maximum value of the current of the armature winding 4 is unchanged. As shown in fig. 5a, the motor with the auxiliary weak magnetic member needs a direct axis demagnetizing current 120A to reach a given speed under the weak magnetic control, and the current change is relatively stable; as shown in fig. 5b, the motor direct axis current without auxiliary weak magnetic member requires the direct axis demagnetizing current 550A to reach a given speed under the weak magnetic control, and the current waveform has large fluctuation. Therefore, the linear motor with the auxiliary weak magnetic member in the embodiment of the invention can save the weak magnetic current 430A under the weak magnetic control, that is, the proportion of the weak magnetic current in the armature winding current is smaller, so that the motor can obtain larger thrust in the weak magnetic control, and can more easily reach a given speed.
Through the analysis, the linear motor with the auxiliary weak magnetic part has a better weak magnetic effect than the linear motor without the auxiliary weak magnetic part, and the weak magnetic current is saved, so that the motor is more easy to accelerate.
Example two
In the linear motor with the auxiliary weak magnetic structure, the magnetic part 2 covered on the surface of the secondary magnetic pole 1 is made of permalloy, and compared with silicon steel, the permalloy has slightly lower saturation magnetic induction intensity, but the permeability is dozens of times higher than that of the silicon steel, and the iron loss is 2 to 3 times lower than that of the silicon steel. The auxiliary weak magnetic part made of permalloy also provides a low-reluctance magnetic circuit for the armature magnetic field and the secondary permanent magnet magnetic field, can help demagnetizing current to offset a part of permanent magnet flux linkage, increases direct-axis inductance, enhances armature reaction, and can play a role in auxiliary weak magnetic.
EXAMPLE III
The embodiment of the invention provides a bilateral coreless permanent magnet linear synchronous motor, and as shown in fig. 3, a linear motor with an auxiliary weak magnetic structure is simulated by using Maxwell software, wherein the simulation conditions are the same as those of the unilateral coreless permanent magnet linear synchronous motor in the specific implementation mode, and according to the simulation result, a direct-axis inductance L of the linear motor with the auxiliary weak magnetic part (magnetic part 2) in the embodiment of the invention is providedd1Linear motor direct axis inductance L without auxiliary weak magnetic member at 5.817 mu Hd25.474 muH, therefore, for the bilateral coreless permanent magnet linear motor, the direct-axis inductance of the linear motor with the auxiliary weak magnetic part is increased, and the armature reaction is enhanced, so that compared with the existing linear motor without the auxiliary weak magnetic part, the bilateral coreless permanent magnet linear synchronous motor of the embodiment of the invention improves the weak magnetic performance, can be used for occasions needing the weak magnetic acceleration of the motor, and is easy to accelerate the motor.
According to the linear motor with the auxiliary weak magnetic structure, the magnetic part 2 is arranged on the surface of the secondary magnetic pole 1 to form the auxiliary weak magnetic structure, so that the demagnetizing current can more effectively offset the magnetic flux of the permanent magnet, the linear motor is suitable for the traction occasions of rail transit vehicles, such as the traction of magnetic suspension trains and subway vehicles, and the motor can reach higher speed under the limitation of the DC bus voltage of the inverter. The auxiliary weak magnetic structure can provide a low-reluctance magnetic circuit for an armature magnetic field, so that the direct-axis inductance is increased, and the armature reaction is further enhanced. And because the linear motor is a synchronous linear motor, the secondary and the traveling wave magnetic field move synchronously, and the magnetic part covered on the secondary magnetic pole does not increase extra eddy current loss and hysteresis loss.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (7)

1. A linear motor having an auxiliary flux weakening structure, comprising: a secondary magnetic pole (1), a magnetic part (2), a primary tooth slot (3) and an armature winding (4);
the armature winding (4) is fixed on the primary tooth slot (3);
the secondary magnetic pole (1) is arranged on one side or two sides of the armature winding (4), and an air gap is formed between the first side of the secondary magnetic pole (1) and the armature winding (4);
the magnetic part (2) is arranged on the surface of a second side of the secondary magnetic pole (1), wherein the first side is the side, close to the armature winding (4), of the secondary magnetic pole (1), the second side is the side, far away from the armature winding (4), of the secondary magnetic pole (1), and the auxiliary weak magnetic structure is the magnetic part (2);
the secondary pole (1) comprises: a plurality of unit permanent magnets (11) arranged according to a Halbach array;
the magnetic pieces (2) are correspondingly and adaptively covered on the surfaces of the unit permanent magnets (11) respectively;
each unit permanent magnet (11) is covered with one magnetic part (2), each magnetic part (2) is covered on one unit permanent magnet (11) with the same length and width, and a gap between every two adjacent unit permanent magnets (11) does not cover the magnetic part (2);
the primary tooth grooves (3) are coreless primary tooth grooves.
2. The linear motor having an auxiliary flux weakening structure as claimed in claim 1, characterized in that the material of said magnetic member (2) is a soft magnetic material.
3. The linear motor having an auxiliary flux weakening structure as claimed in claim 2, wherein the material of said magnetic member (2) comprises: silicon steel sheet, permalloy sheet, magnetic steel, and soft magnetic ferrite.
4. The linear motor having an auxiliary flux weakening structure as claimed in claim 1, wherein a plurality of said unit permanent magnets (11) are arranged in close alignment or spaced apart by a predetermined distance.
5. The linear motor having an auxiliary flux weakening structure as claimed in claim 1, wherein said magnetic member (2) has a form including: whole block type, laminated type, and several strip type.
6. The linear motor having an auxiliary flux weakening structure as claimed in claim 1, wherein the thickness of said magnetic member (2) is a preset thickness, said preset thickness being smaller than the thickness of said secondary magnetic pole (1).
7. The linear motor having an auxiliary flux weakening structure as claimed in claim 1, wherein both sides of said armature winding (4) and said secondary pole (1) form two said air gaps of equal width.
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