Induction motor

Abstract

The invention discloses an induction motor, and relates to the field of motors, the induction motor comprises a stator and a rotor, and the rotor is of a solid structure which is integrally formed, smooth in surface and free of grooves or hollows through a processing technology. The side face, away from the stator, of the rotor is connected with the output shaft. The stator is arranged on one side of the rotor, and the other side of the rotor is connected with the output shaft. The windings of the stator adopt a two-phase four-wire form, and any two adjacent wire ends are connected in four wire ends after the opposite windings are reversely connected. And the three wire ends are connected with a three-phase full-bridge drive. And the frame part of the stator and the rotor are made of one of red copper, brass, pure aluminum, aluminum alloy 6061, aluminum alloy 7075, No.45 steel, A3 steel, electrical pure iron and martensitic stainless steel. On the basis of not using a permanent magnet to reduce the manufacturing cost, the two-phase four-wire stator is adopted to drive the integrally formed metal rotor, so that the material cost and the manufacturing cost of the motor are greatly reduced, and the motor is suitable for various occasions such as high temperature and high rotating speed.

Description

Technical Field

[0001] The present invention relates to the field of motors, and particularly to an induction motor. Background Art

[0002] Motors without permanent magnets mainly work based on the principle of electromagnetic induction. They generally include two parts: a stator and a rotor. The stator is the stationary part, which is composed of a core laminated with silicon steel sheets and coils wound around the core. When these coils are energized, a magnetic field will be generated. The rotor is the rotating part, usually composed of a squirrel-cage type or winding made of conductive materials. When the stator winding is energized, according to the right-hand screw rule, a magnetic field will be formed around the stator. Under the action of the stator magnetic field, according to Faraday's law of electromagnetic induction, an electromotive force will be induced in the rotor conductor. When the rotor conductor cuts the stator magnetic field, an induced current will be generated in the rotor conductor. Then, according to the left-hand rule, the induced current will be subjected to a force in the magnetic field, and this force will generate a torque to drive the rotor to rotate. When the direction of the induced current in the rotor conductor is perpendicular to the direction of the stator magnetic field, the maximum torque will be generated. The motor drive changes the energization phase sequence of the stator coil in a timely manner according to the position information of the rotor, so that the rotor can continue to rotate.

[0003] Two-phase four-wire windings are usually used in synchronous stepper motors. Such motors generate a magnetic field through two sets of windings (each with two terminals) on the stator, which interact with the permanent magnets on the rotor to achieve precise stepper motion. Summary of the Invention

[0004] An induction motor according to the present invention includes:

[0005] A stator, the stator includes two or more poles, and a plurality of stator windings corresponding to the poles;

[0006] A rotor, the rotor is coaxially arranged with the stator, the rotor is arranged to face the stator winding, and rotates along the coaxial direction, generating a relative displacement with the stator winding;

[0007] The rotor is processed by integral molding and is a solid structure with a smooth surface, without slots or hollowing.

[0008] Further, the rotor is cylindrical, enclosing the stator therein, and the side of the rotor facing away from the stator is connected to the output shaft.

[0009] Further, the rotor is rod-shaped and is surrounded by the stator.

[0010] Further, the rotor is disc-shaped, the stator is arranged on one side of the rotor, and the other side is connected to the output shaft.

[0011] Further, the induction motor includes a first stator and a second stator. The rotor is disc-shaped, and the first stator and the second stator are arranged on both sides of the rotor. The output shaft of the rotor penetrates through the first stator and the second stator.

[0012] Further, the induction motor includes a first rotor and a second rotor. Both the first rotor and the second rotor are disc-shaped. The first rotor and the second rotor are arranged on both sides of the stator, and the first rotor and the second rotor are respectively provided with output shafts in directions away from the stator.

[0013] Further, the stator winding adopts a two-phase four-wire form. Among the four wire heads after the opposite windings are reversely connected, any two adjacent wire heads are connected, and three wire heads are formed with the remaining two wire heads.

[0014] Further, the three wire heads are connected to a three-phase full-bridge drive.

[0015] Further, the wire heads pinched together are called the third phase. The third phase is connected to a constant DC voltage that is half of the other two phases. The other two phases are driven with a 90-degree phase shift.

[0016] Further, the third phase is separately connected to a half-bridge drive, and the duty cycle of the waveform of this half-bridge is 50%.

[0017] Further, for the drive waveforms of the stator, excluding the two phases other than the phase with the pinched wire heads, one of the phases provides the peak current of the stator but its rate of change is zero, and the other phase provides the excitation current, and the amplitude of its stator part is zero but the rate of change is the largest.

[0018] Further, the drive waveform of the stator is a non-sinusoidal waveform containing harmonic components, and eddy currents of different intensities are induced at different positions of the rotor.

[0019] Further, when the wavelength of the harmonic matches the size of the rotor, concentrated eddy currents are generated deep inside the rotor.

[0020] Further, the frame part of the stator and the material of the rotor are one or a combination of red copper, brass, pure aluminum, aluminum alloy 6061, aluminum alloy 7075, 45 steel, A3 steel, pure iron for electrical engineering, and martensitic stainless steel.

[0021] On the basis of not using permanent magnets to reduce the manufacturing cost, in order to further reduce the manufacturing cost, the present invention uses a two-phase four-wire stator to drive an integrally formed metal rotor, so that the material cost and manufacturing cost of the motor are greatly reduced, and it is applicable to various occasions such as high temperature and high speed.

[0022] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, features and effects of the present invention. Description of the Drawings

[0023] Figure 1 is a schematic diagram of an inner stator cooperating with a cylindrical outer rotor according to a preferred embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of an outer stator cooperating with a rod-shaped inner rotor according to a preferred embodiment of the present invention;

[0025] Figure 3 is a schematic diagram of a single stator and single rotor of a disc motor according to a preferred embodiment of the present invention;

[0026] Figure 4 is a schematic diagram of a double stator and single rotor of a disc motor according to a preferred embodiment of the present invention. Detailed Description of the Preferred Embodiments

[0027] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings of the specification to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned in the text.

[0028] In the drawings, components with the same structure are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. To make the illustration clearer, the thickness of some parts in the drawings is appropriately exaggerated.

[0029] Embodiment 1

[0030] An induction motor described in this embodiment includes a stator and a rotor, with the stator inside and the rotor outside. As Figure 1 shown, the stator winding adopts a two-phase four-wire form, that is, eight wire ends A1, A2, B1, B2, C1, C2, D1, D2 of four wires A, B, C, D. Among them, A2 and D2 are connected, and B2 and C2 are connected to form two independent wires A1A2D2D1 and B1B2C2C1. At this time, A1 and B1 among the remaining four wire ends A1, B1, C1, D1 are connected or C1 and D1 are pinched together to form one wire end (one phase), and the other two wire ends (two phases).

[0031] The drive adopts any one of three methods. The first method is that three wire ends are connected to a three-phase full-bridge drive, which is powered by a three-phase AC power supply and includes six power switches. Each phase is connected to two switches. The on-off states of the six power switches are controlled through PWM waveforms to control the phase current, thereby controlling the rotation speed and torque of the outer rotor. The second method is four-phase control, with a 90-degree phase difference between every two phases. The third phase is actually the inverse phase of the first phase, and the fourth phase is the inverse phase of the second phase. Therefore, it can be reduced to two-phase control. The wire ends pinched together are called the third phase, and the third phase is connected to a constant DC voltage that is half of the other two phases. The other two phases are driven with a 90-degree phase shift to achieve a rotating magnetic field. The third method is that the third phase is separately connected to a half-bridge drive. The duty cycle of the waveform of this half-bridge is 50%, and the rest is the same as the second method.

[0032] The windings of the stator described in this embodiment can also be repeatedly stacked with more levels, such as three levels and six windings.

[0033] In the radial flux design, the rotor described in this embodiment adopts a cylindrical structure, as Figure 1 shown. The cylindrical barrel wall is coaxial with the stator. The stator is installed inside the cylindrical rotor. The side of the bottom of the cylindrical rotor facing away from the stator is connected to the output shaft, and this output shaft is also coaxial with the stator.

[0034] The stator (excluding the frame part after winding) and the cylindrical rotor described in this embodiment are integrally formed by processing methods such as cutting, casting, or forging. The surface is smooth, without grooves, not hollowed out, and is a solid structure.

[0035] The materials of the stator (excluding the frame part after winding) and the solid rotor described in this embodiment are red copper or brass, pure aluminum, aluminum alloy 6061, aluminum alloy 7075, 45 steel, A3 steel, pure iron for electrical engineering, martensitic stainless steel, etc.

[0036] In this embodiment, the stator and the solid rotor are combined. After alternating current is applied to the two-phase four-wire winding stator, an alternating magnetic field will be generated in the stator core. Due to the spatial distribution of the two-phase windings and the current phase difference, these magnetic fields will synthesize a rotating magnetic field. Under the action of the rotating magnetic field, the conductive materials inside the solid metal rotor will cut the magnetic force lines. According to Faraday's law of electromagnetic induction, an electromotive force will be induced in the conductor when the conductor cuts the magnetic force lines. The induced electromotive force will form eddy currents, that is, induced currents, in the solid metal rotor. These currents flow inside the solid rotor and are affected by the Lorentz force in the magnetic field. The magnetic field generated by the induced current interacts with the rotating magnetic field of the stator to form an electromagnetic torque, which drives the solid rotor to rotate. The drive waveform of the stator described in this embodiment excludes the other two phases except the phase where the wire ends are pinched. One of them provides the peak current of the stator but its rate of change is zero, and the other provides the excitation current. The amplitude of its stator part is zero but the rate of change is the largest. Therefore, the induced current in the solid rotor described in this embodiment is not only concentrated on the surface of the material, but also coupled to the inside of the solid rotor, so the overall resistance is small and the eddy current loss is not large.

[0037] Eddy currents exist in all electrical equipment that utilizes the principle of electromagnetic induction. The existence of eddy currents mainly affects the utilization rate of electrical energy in AC circuits. Because eddy currents can generate Joule heat, and the generated heat is proportional to the square of the current. The more heat generated by eddy currents, the more waste of electrical energy, and the worse the conversion efficiency between electrical energy and mechanical energy. Therefore, in the traditional design of induction motors, the rotor core is usually stacked by silicon steel sheets, and several slots are distributed on the rotor core, and rotor windings are installed in the slots. The purpose of this design is to minimize the generation of eddy currents, thereby reducing the heat energy loss caused by eddy currents.

[0038] Different from the design of the above-mentioned traditional induction motor, this embodiment adopts a solid rotor design. Since the drive waveform of the induction motor has a significant impact on the spatial position distribution of the fundamental eddy current and harmonic eddy current in the solid rotor, when the drive waveform is an ideal sine wave, the fundamental magnetic field is sinusoidally distributed in space. The fundamental eddy current induced by the fundamental magnetic field in the solid rotor is mainly concentrated on the surface of the solid rotor, and its distribution is closely related to the spatial distribution of the fundamental magnetic field. Usually, the eddy current density is larger in the region with higher magnetic field intensity. If the drive waveform is not an ideal sine wave but a non-sine waveform containing harmonic components, the distribution of the fundamental magnetic field will be disturbed, and these harmonic components will induce additional eddy currents in the solid rotor, thereby changing the spatial distribution of the fundamental eddy current.

[0039] The harmonic components in the driving waveform will generate harmonic magnetic fields between the stator and the solid rotor. The spatial distributions of harmonic magnetic fields with different orders are different. For example, the induced eddy current distributions of the 5th and 7th harmonic magnetic fields in the solid rotor are different from the fundamental wave eddy current distribution. Generally speaking, the spatial distribution of higher-order harmonic magnetic fields is more complex, and eddy currents with different intensities will be induced at different positions in the solid rotor.

[0040] The spatial position distribution of harmonic eddy currents in the solid rotor depends on the wavelength of the harmonic magnetic field and the geometric structure of the solid rotor. For certain specific harmonic orders, their wavelengths may match the size of the solid rotor, resulting in a strong local concentration of eddy currents at certain specific positions (deeper inside, not on the surface) of the solid rotor. This locally concentrated eddy current will cause local overheating of the solid rotor. However, since the solid rotor is used in this embodiment, although the local eddy current is large, due to the very small resistance of the solid as a whole, the heat generated by the eddy current will be greatly reduced.

[0041] Embodiment 2

[0042] An induction motor described in this embodiment includes a stator and a rotor, with the stator on the outside and the rotor on the inside. As Figure 2 shown, the winding form of the stator is the same as that in Embodiment 1. The rotor adopts a rod-shaped structure, which is a standard solid cylinder with a smooth surface, no slots, no hollowing, and is a solid structure. The cylindrical rotor is coaxial with the surrounding stator and can directly output. The rest of the induction motor described in this embodiment is the same as that in Embodiment 1.

[0043] Embodiment 3

[0044] In the axial flux design, as Figure 3 shown, the rotor described in this embodiment adopts a disc-shaped solid structure. The disc-shaped solid rotor is coaxial with the stator. One side of the disc-shaped solid rotor is in contact with the stator, with an air gap reserved in the middle, and the other side is connected to the output shaft. The rest of the induction motor described in this embodiment is the same as that in Embodiment 1.

[0045] Embodiment 4

[0046] In the axial flux design, as Figure 4 shown, the rotor described in this embodiment adopts a disc-shaped solid structure. The disc-shaped solid rotor is coaxial with two stators. Both sides of the disc-shaped rotor are in contact with the two stators respectively, with an air gap reserved in the middle. The middle part of the two stators is left empty, and the middle disc-shaped rotor is connected to the output shaft to output mechanical rotation to one side or both sides. The rest of the induction motor described in this embodiment is the same as that in Embodiment 1.

[0047] Embodiment 5

[0048] In the axial flux design, which is not shown in the drawings, as a variant of the fourth embodiment, this embodiment adopts a configuration form of a single stator attached to double-sided disc-shaped rotors. The single stator has a disc-shaped frame, with windings arranged on both sides thereof, or the same winding penetrates the frame where the stator is located. The double-sided disc-shaped rotors are respectively attached to the stator frame and the windings, and mechanical rotations are output to both sides respectively.

[0049] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. An induction motor, comprising: A stator, the stator comprising two or more poles and a plurality of stator windings corresponding to the poles; A rotor, the rotor is coaxially arranged with the stator, the rotor is arranged to face the stator winding and rotate along the coaxial axis to generate relative displacement with the stator winding; The feature of the invention is that the rotor is processed by one-piece molding and has a smooth surface and a solid structure without slots or hollowing.

2. The induction motor according to claim 1, characterized in that The rotor is cylindrical and surrounds the stator. The side of the rotor facing away from the stator is connected to the output shaft.

3. The induction motor according to claim 1, characterized in that The rotor is in a stick shape and is surrounded by the stator.

4. The induction motor according to claim 1, characterized in that The stator winding adopts a two-phase four-wire form. Among the four wire ends after the relative windings are reversed and connected, any two adjacent wire ends are connected to form three wire ends with the remaining two wire ends.

5. The induction motor according to claim 4, characterized in that The three wire ends are connected to a three-phase full-bridge drive.

6. The induction motor according to claim 4, characterized in that The wire ends pinched together are called the third phase, and the third phase is connected to a constant DC voltage half of the other two phases, and the other two phases are driven at a 90-degree offset.

7. The induction motor according to claim 4, characterized in that The third phase is connected to a half-bridge driver separately, and the duty cycle of the half-bridge waveform is 50%.

8. The induction motor according to claim 6, characterized in that The driving waveform of the stator excludes the other two phases of the phase with pinched wire ends, one of which provides the stator peak current but its change rate is zero, and the other phase provides the excitation current, the stator part of which has zero amplitude but the largest change rate.

9. The induction motor according to claim 1, characterized in that The driving waveform of the stator is a non-sinusoidal waveform containing harmonic components, which induces eddy currents of different intensities at different positions of the rotor.

10. The induction motor according to claim 9, characterized in that When the wavelength of the harmonics matches the size of the rotor, concentrated eddy currents are generated deep inside the rotor.

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