Long primary bilateral linear induction motor with sandwich-type secondary

Abstract

The invention provides a long primary bilateral linear induction motor with a sandwich-type secondary. The long primary bilateral linear induction motor comprises a long primary, an air gap and a sandwich-type short secondary. The long primary is composed of an iron core and a three-phase or multi-phase winding. The short secondary is a sandwich type secondary and is placed between the long primary bodies on the two sides, and air gaps of the motor are formed between the long primary bodies and the short secondary. The long primary winding adopts a back winding type winding or a distributed winding, the secondary adopts a sandwich type structure, the short secondary is formed by improving a traditional flat short secondary, and the resistance of the end part of the short secondary is smaller than the resistance in a coupling region of the primary and the short secondary by forming an integral slot in the center of the short secondary; therefore, the second-type transverse edge end effect can be effectively overcome, and the air-gap magnetic field and the thrust of the motor are improved.

Description

Technical Field

[0001] The present invention relates to a linear induction motor, and particularly to a long-primary bilateral linear induction motor with a sandwich-type secondary. Background Art

[0002] A linear induction motor is a transmission device that directly converts electrical energy into linear motion mechanical energy without any intermediate conversion mechanism, and can be used in any occasion that requires linear drive.

[0003] A linear induction motor can be regarded as evolved from a rotary induction motor. Figure 3a Compared with Figure 3b The double-sided long-primary linear induction motor of the prior art mainly consists of a long primary, an air gap, and a short secondary. The long primary is equivalent to the stator of a rotary induction motor and is arranged on both sides of the track, including a core with teeth and slots, and windings embedded in the core slots. Usually, a traditional distributed winding ( Figure 3b ), or a back-wound winding ( Figure 3a ) can be used. The short secondary, also called the mover, is equivalent to the rotor of a rotary induction motor and is usually composed of a flat conductor plate ( Figure 5a ), such as an aluminum plate or a copper plate, and is a reaction plate for electromagnetic induction. The short secondary is placed between the double-sided long primaries, and the gap therebetween is the air gap of the motor. When a sinusoidal alternating current is passed through the winding, a traveling wave magnetic field is generated in the air gap, causing an induced electromotive force and eddy currents to be generated in the secondary conductor plate. The eddy currents interact with the air gap magnetic field to generate an electromagnetic thrust to drive the secondary reaction plate to move.

[0004] However, due to the discontinuous structure of the primary or secondary of the linear motor, a discontinuous magnetic field will be generated in the air gap during the operation of the motor, and then special electromagnetic field phenomena different from those of the rotary motor, such as the transverse end effect and the longitudinal end effect, will occur. For example, the reason for the generation of the second type of transverse end effect is that a part of the secondary eddy current closes within the coupling region between the secondary and the primary, resulting in a saddle-shaped distribution of the synthesized air gap magnetic field, causing distortion of the air gap magnetic field and a decrease in the air gap magnetic density, and thus reducing the thrust of the motor.

[0005] In order to reduce the second type of lateral end effect, it is possible to make the resistance of the end of the secondary induction plate of the linear induction motor much smaller than the resistance of the coupling region. The commonly used methods are as follows: increasing the size of the end of the secondary induction plate so that it is larger than the width of the primary iron core to reduce the end resistance, or using transverse slots in the secondary to increase the resistance in the coupling region. Both of the above methods can weaken the second type of lateral end effect. However, for the first method, under certain conditions where the installation space is limited or the requirement for high-speed operation stability is relatively high, the secondary cannot reach the required width, resulting in a relatively obvious second type of lateral end effect and a greater impact on the motor performance; while the second method makes the secondary structure more complex, and the manufacturing process difficulty and cost of the secondary will increase significantly. Summary of the Invention

[0006] Aiming at the defects of the prior art, while keeping the primary structure of the long-primary double-sided linear induction motor unchanged, in order to weaken the second type of lateral end effect and improve the stability of the motor during high-speed operation, the present invention proposes a long-primary double-sided linear induction motor with a sandwich-type secondary. The present invention is beneficial to weakening the second type of lateral end effect and improving the air-gap magnetic field, and thus is beneficial to improving the thrust density of the motor.

[0007] The technical solution of the present invention is: a long-primary double-sided linear induction motor with a sandwich-type secondary, including double-sided long primaries, an air gap, and a sandwich-type short secondary. The three-phase or multi-phase windings of the long primaries are placed in the iron-core slots to form the long stator of the motor; the toothed-slot iron core is laminated by silicon steel sheets; the long-primary windings are back-wound windings, and can also be single-layer or double-layer distributed windings; the short secondary adopts a sandwich-type structure, and the unslotted area is made of conductive materials such as aluminum and copper; the slotted area can be filled with non-ferromagnetic substances such as epoxy resin and wood, or can be filled with ferromagnetic materials such as silicon steel sheets, pure iron, and magnetic steel, etc.; the double-sided long primaries are placed on the ground, and the short secondary is fixed on the driven object. The air gap between the long primaries and the short secondary forms the long-primary double-sided linear induction motor.

[0008] Its further technical solution also lies in:

[0009] The primary armature winding is three-phase or multi-phase, and the armature winding is of a back-wound structure, and can also be a single-layer or double-layer distributed winding.

[0010] The short secondary adopting a sandwich-type structure is composed of a slotted area and an unslotted area.

[0011] The beneficial effects of the present invention are as follows:

[0012] Adopt a sandwich - type structure short secondary, and its slotted area can effectively increase the resistance in the coupling area of the short secondary, so that the eddy current induced in the short secondary can be closed outside the coupling area, thereby weakening the second - type lateral edge - end effect, reducing the loss of the secondary induction plate, and improving the motor performance. When the slotted area is filled with ferromagnetic material, it can provide a magnetic conduction path for the long - primary double - side linear induction motor, thereby reducing the equivalent electromagnetic air - gap of the motor and further improving the thrust of the motor. Brief Description of the Drawings

[0013] Figure 1a is a cross - sectional view of the motor of the present invention;

[0014] Figure 1b is a cross - sectional view of the motor of the present invention, and the long primary adopts a distributed winding;

[0015] Figure 2 is a three - dimensional structure schematic diagram of the motor of the present invention;

[0016] Figure 3a is a cross - sectional view of the motor of the prior art, and the long primary adopts a back - wound winding;

[0017] Figure 3b is a cross - sectional view of the motor of the prior art, and the long primary adopts a distributed winding;

[0018] Figure 4a is a cross - sectional view of the flat short secondary of the motor of the prior art;

[0019] Figure 4b is a cross - sectional view of the sandwich - structure secondary of the motor of the present invention;

[0020] Figure 5a is a top - view of the flat secondary of the motor of the prior art;

[0021] Figure 5b is a top - view cross - sectional view of the sandwich - structure secondary of the motor of the present invention;

[0022] Figure 6a is a cross - sectional view of the back - wound double - side long primary of the motor of the present invention;

[0023] Figure 6b is a cross - sectional view of the back - wound double - side long primary and the sandwich - structure short secondary of the motor of the present invention;

[0024] Figure 7 is a schematic diagram of the eddy - current distribution and the transverse distribution of the air - gap magnetic - flux density in the flat short secondary;

[0025] Figure 8 is a schematic diagram of the eddy - current distribution and the transverse distribution of the air - gap magnetic - flux density under ideal conditions;

[0026] Figure 9It is the thrust calculation result of the prior art motor and the motor of the present invention.

[0027] In the figure, the reference numerals are as follows:

[0028] Long primary 1, air gap 2, short secondary 3, winding 11, iron core 12, unslotted area 31, slotted area 32. Specific embodiments

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, the present invention adopts the following technical solutions.

[0030] As Figure 2 shown, the long-primary bilateral linear induction motor with a sandwich-type secondary of the present invention has a long-primary and short-secondary structure. Its long-primary winding adopts a back-wound type, or a single-layer or double-layer distributed winding can also be used. The three-phase or multi-phase armature windings of the long primary are placed in the toothed iron core to form the long stator of the motor, as Figure 6a shown in Figure 6b ; the toothed iron core is laminated from silicon steel sheets. The short secondary adopts a sandwich structure, as Figure 5b shown, its unslotted area is made of conductive materials such as aluminum and copper, and the slotted area can be filled with non-ferromagnetic substances such as epoxy resin and wood, or can be filled with ferromagnetic materials such as silicon steel sheets, pure iron, and magnetic steel. The double-sided long primary is placed on the ground, the short secondary is fixed on the driven object, and the air gap of the motor is between the long primary and the short secondary. As Figure 1a shown in Figure 1b and shown, the motor of the present invention is vertically placed, wherein the thickness

[0031] of the slotted area is less than the total thickness d of the secondary reaction plate.

[0032] The back-wound type winding is different from the traditional distributed winding. Its characteristic is that the coils are arranged around the iron core. One side of the coil is embedded in the iron core slot, and the other side is wound around the outside and back of the iron core yoke. The coils are connected into one body by connecting wires to form a complete stator winding.

[0033] The short secondary is the reaction plate of the linear induction motor. Its unslotted area is made of conductive materials such as aluminum and copper, and the slotted area can be filled with non-ferromagnetic materials such as epoxy resin and wood, or ferromagnetic materials such as silicon steel sheets, pure iron, magnetic steel, etc. The secondary generates induced electromotive force and eddy current under the cutting of the air gap traveling wave magnetic field. The eddy current interacts with the air gap magnetic field to generate electromagnetic thrust to drive the secondary movement.

[0034] When eddy current flows through the secondary reaction plate, the secondary reaction plate will affect the lateral distribution of the air gap magnetic field, which is called the second type of lateral end effect. If the resistance of the lateral end of the secondary reaction plate that extends out of the primary core in the lateral direction is zero, that is, the end of the reaction plate is made of superconducting material, and the secondary reaction plate has resistance only within the primary core range (that is, the effective range) (the so-called ideal situation), the current distribution in the reaction plate is as follows: Figure 8 As shown in (a), the current distribution in the effective range is parallel, that is, there is only a component in the Y-axis direction. Corresponding to such a current distribution, the distribution of the no-load air gap density along the horizontal direction is as follows Figure 8 As shown in (b), it can be seen that in the absence of end resistance, the introduction of the secondary reaction plate only changes the amplitude of the synthetic air gap flux density (from B Z0 Change to B Z ), without changing the shape of its distribution.

[0035] In practice, the ends of the secondary reaction plates are unlikely to be made of superconducting materials and are often made of the same material as the active parts, such as Figure 5a As shown, there is also resistance at the end. Due to the existence of end resistance, the current distribution in the secondary reaction plate is as follows Figure 7 As shown in (a), the secondary current has not only a Y-axis component but also an X-axis component within the effective width range la, and part of the secondary reaction plate current is closed within the effective width. Figure 7 The current distribution in (a) shows that the resultant air gap flux density is saddle-shaped, as shown in Figure 7 b, which is consistent with the no-load air gap magnetic flux distribution (such as Figure 7 This non-parallel distribution of secondary current and the uneven distribution of air gap flux density along the Y-axis are called the second type of lateral end effect, also known as the dynamic lateral end effect.

[0036] The second type of lateral end effect reduces the total magnetic flux of the linear induction motor, reduces the output power and thrust, and reduces the thrust density. At the same time, it increases the loss of the secondary reaction plate and reduces the motor efficiency.

[0037] To reduce the second type of lateral end effect, a certain number of rectangular slots can be opened in the center of the secondary reaction plate, that is, a grid-type secondary is made to increase the resistance in the coupling area and can play a role in regulating the secondary eddy current. However, the grid-type secondary has a more complex structure and higher manufacturing cost than the flat-type secondary.

[0038] The present invention adopts a sandwich-type secondary, and an integral slot is opened in the center of the secondary reaction plate to form a slotted area. Without changing the end structure of the secondary, the resistance at the end of the secondary reaction plate can also be made smaller than the resistance in the coupling area, which helps to improve the second type of lateral edge effect and increase the thrust density.

[0039] The short secondary of the present invention includes two parts: a slotted area and an unslotted area, as Figure 4b shown in Figure 5b . The shaded part is the slotted area. Among them: the unslotted area is made of conductive materials such as aluminum and copper; the slotted area can be filled with non-ferromagnetic substances such as epoxy resin and wood, or can be filled with ferromagnetic materials such as silicon steel sheets, pure iron, and magnetic steel.

[0040] By adopting a sandwich-type secondary and making the thickness of the integral slot in the center smaller than the thickness of the secondary reaction plate, the second type of lateral edge effect can be weakened to the greatest extent. When the slotted area is filled with ferromagnetic materials, the magnetic conduction loop of the long-primary double-sided linear induction motor can also be shortened, which is beneficial to reducing the equivalent electromagnetic air gap, increasing the air-gap magnetic density, further enhancing the thrust, and improving the motor efficiency.

[0041] The end resistance of the short secondary is less than the resistance of the coupling area , and the resistance of the coupling area . Among them, the resistance of the slotted sandwich coupling area is less than the resistance of the unslotted coupling area, that is .

[0042] The height of the slotted area is the same as the height of the iron core, and the position of the slotted area corresponds to the iron core.

[0043] Embodiment 1

[0044] Embodiment 1 of the present invention is as Figure 1a shown. The motor is vertically placed and adopts a back-wound winding form. The cross-section of the entire motor is as Figure 6b shown.

[0045] The motor of the present invention has a structure of a long primary 1 and a short secondary 3. The double-sided long primary 1 is placed on the ground, and the short secondary 3 is fixed on the driven object. The air gap 2 of the motor is between the long primary 1 (also called the long stator) and the short secondary 3 (also called the short mover).

[0046] Its long primary 1 is composed of a three-phase armature winding 11 and an iron core 12. The toothed-slot iron core 12 is laminated from silicon steel sheets. The three-phase armature winding 11 is a back-wound type. The winding 11 is arranged around the iron core 12. One side of the winding 11 is embedded in the iron core slot, and the other side is wound around the outer side and the back of the yoke of the iron core 12. The windings 11 are connected into one body by connecting wires to form a complete stator winding.

[0047] The short secondary 3 adopts a sandwich structure, such as Figure 4b shown, and is composed of an unslotted area 31 and a slotted area 32. The unslotted area 31 is made of a conductive material such as aluminum or copper, and the slotted area 32 is filled and made of a non-ferromagnetic material. The thickness of the slotted area 32 is less than the total thickness d of the secondary reaction plate. Figure 4a is a cross-sectional view of the flat short secondary of a prior art motor. The thickness d of the secondary reaction plate, Figure 4b in which, is the length of the primary-secondary coupling region, is the length that each end of the secondary extends out of the primary iron core.

[0048] To reduce the second type of transverse end effect, the resistance in the mover coupling region should be increased as much as possible. The primary of the motor with a sandwich secondary is the same as that of the motor with a flat secondary. Since the resistivity of the conductive materials of the sandwich secondary and the flat secondary is the same, and the center of the slotted area of the sandwich secondary is slotted, resulting in a reduction in the cross-sectional area of the eddy current in the mover coupling region, the resistance in its coupling region increases. The resistance in the end region is smaller than the resistance in the coupling region. In this way, it drives the eddy current to close outside the coupling region, weakening the influence of the second type of transverse end effect on the motor.

[0049] The finite element method is used to calculate and compare the actual operating thrust of the motor with a flat secondary and the sandwich structure secondary (filled with ferromagnetic material) of the present invention. The calculation results are as Figure 9 shown. By comparison, it can be seen that the thrust of the motor with the sandwich structure secondary of the present invention increases, about 57.85% increase, proving the effect of the present invention.

[0050] The implementation of the present invention can reduce the influence of the second type of transverse end effect, and can also fill ferromagnetic materials to shorten the equivalent electromagnetic air gap, ensure the motor thrust and thrust density, and improve the high-speed stable operation ability of the long primary double-sided linear induction motor.

[0051] Example 2

[0052] Change the long primary back-wound winding in Example 1 to a traditional single-layer or double-layer distributed winding, such as Figure 1b shown. And the short secondary adopts the structure of the present invention, and the same improvement effect can be obtained.

Claims

1. A long primary double-sided linear induction motor with a sandwich-type secondary, characterized in that: The invention comprises a long primary, an air gap and a sandwich-type short secondary. The three-phase or multi-phase armature winding of the long primary is placed in a primary iron core with tooth slots to form a long stator of the motor. The primary iron core with tooth slots is stacked by silicon steel sheets. The short secondary constitutes a short mover of the motor. The sandwich-type short secondary comprises a slotted part and an unslotted part. The slotted part is filled with non-ferromagnetic material or ferromagnetic material, and the unslotted part is composed of conductive material.

2. The sandwich-type secondary long primary double-sided linear induction motor according to claim 1, characterized in that: The slotted area is made of a flat plate type short secondary integral slot.

3. The sandwich-type secondary long primary double-sided linear induction motor according to claim 1, characterized in that: Grooved area thickness Less than the short secondary total thickness d.

4. The sandwich-type secondary long primary double-sided linear induction motor according to claim 1, characterized in that: The short secondary terminal resistor Smaller than the resistance of the coupling region .

5. The sandwich-type secondary long primary double-sided linear induction motor according to claim 1, characterized in that: The long primary armature winding is back-wound.

6. The sandwich-type secondary long primary double-sided linear induction motor according to claim 1, characterized in that: The long primary armature winding is a single-layer or double-layer distributed winding.

7. The sandwich-type secondary long primary double-sided linear induction motor according to claim 4, characterized in that: Resistance of the coupling region , where the resistance of the slotted sandwich coupling region is less than the resistance of the unslotted coupling region, that is, .

8. The sandwich-type secondary long primary double-sided linear induction motor according to claim 1, characterized in that: The height of the slotted area is the same as the height of the core, and the position of the slotted area corresponds to the core.

9. The sandwich-type secondary long primary double-sided linear induction motor according to claim 1, characterized in that: The slotted area is filled with non-ferromagnetic materials including epoxy resin or wood, and the ferromagnetic material includes silicon steel sheet, pure iron or magnetic steel.

10. The sandwich-type secondary long primary double-sided linear induction motor according to claim 1, characterized in that: The slotted area is made of conductive material including aluminum and copper.

Images