Automatic fault-tolerant permanent magnet synchronous motor for high-torque-density turn-to-turn short circuit fault

Abstract

The invention discloses an automatic fault-tolerant permanent magnet synchronous motor for a high-torque-density turn-to-turn short circuit fault, and belongs to the field of fault-tolerant motors. The motor is a radial magnetic field circular rotating motor, and a stator part of the motor comprises a stator iron core, a stator winding, a magnetic conduction bridge and independent teeth. According to the motor, the automatic fault-tolerant function is achieved through the magnetic conductive bridge, and the torque density of the motor is improved through the independent teeth. When the motor works normally, magnetic circuits in the magnetic conductive bridge offset each other and are completely consistent with the magnetic circuit without the magnetic conductive bridge, the effective magnetic circuit path of the motor is relatively long at the moment, so that the torque density of the motor is relatively low, and the independent teeth are additionally arranged on the stator, so that the magnetic circuit path is shortened, and meanwhile, the path of the magnetic circuit trend is increased; and the torque density of the motor is greatly improved. When a turn-to-turn short circuit occurs in the motor, magnetic circuits in the magnetic conductive bridges cannot offset each other to form a loop, so that short-circuit current can be suppressed, meanwhile, torque, current and voltage hardly change, and capacity-reduction-free output can be realized.

Description

Technical Field

[0001] The present invention belongs to the field of fault-tolerant motors, and more specifically, relates to a radial flux permanent magnet synchronous motor with automatic fault tolerance for turn-to-turn short-circuit faults and relatively high torque density. Technical Background

[0002] In recent years, with the continuous development of permanent magnet synchronous motors, various faults have become the focus of attention, among which turn-to-turn short circuit fault is the most common fault. Turn-to-turn short circuit fault will reduce the output capacity of the motor, asymmetric three-phase voltage and current, aggravate motor vibration, and excessive short circuit current will lead to increased heating and even winding burning. It is also one of the sources of other faults. Therefore, turn-to-turn short circuit fault is extremely harmful to the motor. However, due to the uncertainty of the short circuit position, turn-to-turn short circuit has become the most difficult fault to handle for permanent magnet synchronous motors. At present, axial permanent magnet synchronous motors can achieve automatic fault tolerance in the event of turn-to-turn short circuit faults, and the motor torque, voltage, and current do not change. However, if its principle is directly applied to radial flux and circular rotating motors, the coil side utilization rate of its winding coil is low, resulting in a low torque density of the motor. Therefore, how to make the radial flux permanent magnet synchronous motor automatically fault-tolerant in the event of a turn-to-turn short circuit fault and have a relatively high torque density is a key issue in the field of fault-tolerant motors and needs to be solved urgently. Summary of the invention

[0003] The problem to be solved by the present invention is to provide a high torque density turn-to-turn short circuit fault automatic fault-tolerant permanent magnet synchronous motor.

[0004] In order to solve the above technical problems, the technical solution proposed in the present invention is: a high torque density inter-turn short-circuit fault automatic fault-tolerant permanent magnet synchronous motor, the motor is a circular rotating motor; the motor includes a stator, a rotor and an air gap therebetween; the stator includes a stator core and a stator winding; the stator winding is an m-phase winding, m is an integer greater than or equal to 2, and each phase of the stator winding includes 2z stator coils, z is an integer greater than or equal to 1; a through slot is axially opened on one side of the stator core close to the rotor to form a stator slot and a stator tooth; the stator core includes zm magnetic bridges, each magnetic bridge connects two adjacent stator teeth, and each stator tooth is connected to the magnetic bridge. The number of magnetic bridges does not exceed 1, forming zm stator tooth pairs; the electrical angle value of the axis angle between the two stator teeth included in each stator tooth pair is 340°~380°; the electrical angle value spanned by the tooth top arc length of each stator tooth included in each stator tooth pair is 130°~230°; the stator tooth pairs are evenly distributed along the circumference of the stator core; each magnetic bridge is located at the slot top position of the slot between the two stator teeth connected to it; the two stator teeth included in each pair of stator tooth pairs are each wound with a stator coil; the two stator coils wound on the two stator teeth included in each pair of stator tooth pairs have the same number of turns, the same winding direction, belong to the same phase winding, and are connected in series.

[0005] As a preferred implementation, the per-unit value of the inductance of each stator coil is not less than 2.

[0006] As a preferred embodiment, the stator core contains stator teeth that are not connected to the magnetic bridge, i.e., independent teeth, and the number of the independent stator teeth is equal to the number of pairs of stator teeth; the independent stator teeth and the stator tooth pairs are arranged alternately along the circumference of the stator core; and no stator coil is wound around the independent stator teeth.

[0007] As a preferred embodiment, the electrical angle spanned by the arc length of the tooth top of the independent stator teeth is not less than 110° and not more than 280°.

[0008] The motor using the technical solution described in the invention still has balanced currents in each phase under a turn-to-turn short-circuit fault, and the amplitude and phase are almost the same as those under normal working conditions. Therefore, the torque under a turn-to-turn short-circuit fault is the same as that under normal working conditions, and the short-circuit current is greatly suppressed; the above fault-tolerance process is all automatically realized, so the technical solution described in the invention can make the motor have automatic fault-tolerance capability for turn-to-turn short-circuit. In addition, by cleverly using adjacent stator teeth with an electrical angle difference of about 360° to form a stator tooth pair, a coil side of each stator coil that originally does not bear electromechanical energy conversion is changed to an effective coil side that also bears electromechanical energy conversion, and at the same time using independent stator teeth with a reasonable tooth top angle, the torque density of the motor is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a cross-sectional schematic diagram of the motor described in the first specific embodiment;

[0010] Figure 2 is a cross-sectional schematic diagram of the motor described in the second specific embodiment;

[0011] Figure 3 is a cross-sectional schematic diagram of the motor described in specific embodiment 3;

[0012] Figure 4 is a schematic diagram of the compensation leakage magnetic circuit;

[0013] Figure 5 Schematic diagram of winding connection of the motor described in Embodiments 1, 2 and 3 of the present invention;

[0014] Figure 6 A local area division diagram of the motor model;

[0015] Figure 7 A local schematic diagram of magnetic leakage caused by slotting of the motor;

[0016] Figure 8 It is a local schematic diagram of magnetic leakage between adjacent teeth of the motor.

[0017] In the figure, 1-stator core, 2-rotor core, 3-stator winding, 4-permanent magnet, 5-stator tooth, 6-stator independent tooth, 7-magnetic bridge. DETAILED DESCRIPTION

[0018] A typical embodiment of the present invention provides a high torque density turn-to-turn short-circuit fault automatic fault-tolerant permanent magnet synchronous motor, wherein the motor is a circular rotating motor; the motor comprises a stator, a rotor and an air gap therebetween; the stator comprises a stator core 1 and a stator winding; the stator winding is an m-phase winding, m is an integer greater than or equal to 2, and each phase of the stator winding comprises 2z stator coils 3, z is an integer greater than or equal to 1; a through slot is axially provided on one side of the stator core close to the rotor to form stator slots and stator teeth; the stator core comprises zm magnetic bridges 7, each magnetic bridge connecting two adjacent stator teeth, and each magnetic bridge connected to the stator tooth is The number is no more than 1, forming zm stator tooth pairs 5; the electrical angle value of the axis angle between the two stator teeth included in each stator tooth pair is 340°~380°; the electrical angle value spanned by the tooth top arc length of each stator tooth included in each stator tooth pair is 130°~230°; the stator tooth pairs are evenly distributed along the circumference of the stator core; each magnetic bridge is located at the slot top position of the slot between the two stator teeth connected to it; the two stator teeth included in each pair of stator tooth pairs are each wound with a stator coil; the two coils wound on the two stator teeth included in each pair of stator tooth pairs have the same number of turns, the same winding direction, belong to the same phase winding, and are connected in series.

[0019] According to the above implementation, the motor realizes the automatic fault tolerance function through the magnetic bridge, and improves the torque density of the motor through independent teeth. When the motor is working normally, the magnetic circuits in the magnetic bridge cancel each other out and are completely consistent with the magnetic circuit without the magnetic bridge. At this time, the effective magnetic circuit path of the motor is longer, resulting in a low torque density of the motor. By adding independent teeth to the stator, not only the magnetic circuit path is shortened, but also the magnetic circuit direction is increased, so that the torque density of the motor is greatly improved. When a short circuit occurs between turns of the motor, the magnetic circuits in the magnetic bridge cannot cancel each other out to form a loop, which can suppress the short-circuit current. At the same time, the torque, current, and voltage hardly change, and the output without capacity reduction can be achieved.

[0020] The stator core of the motor may also contain stator teeth that are not connected to the magnetic bridge. In this article, the stator teeth that are not connected to the magnetic bridge are referred to as independent stator teeth. The number of the independent stator teeth is equal to the number of pairs of stator teeth. The independent stator teeth are evenly distributed along the circumference of the stator core, and the independent stator teeth and the stator tooth pairs are alternately arranged along the circumference of the stator core. No stator coils are wound around the independent stator teeth. The electrical angle spanned by the arc length of the tooth top of the independent stator teeth is not less than 110° and not more than 280°.

[0021] The magnetic bridge can be connected to the stator teeth in an integral manner, such as Figure 1 , Figure 2 as well as Figure 4As shown, in this connection mode, the magnetic bridge and the stator core are a whole, so the magnetic bridge and the stator teeth connected thereto are continuous and gap-free. The magnetic bridge can also be connected to the stator teeth in a splicing connection mode, such as Figure 3 As shown, when a splicing connection method is adopted, the magnetic bridge is made of a high magnetic permeability material with a magnetic permeability greater than 1000.

[0022] Each of the magnetic bridges and the two stator teeth connected thereto and the stator yoke together form a compensation leakage magnetic circuit, such as Figure 4 The two series coils wound on a pair of stator teeth form complementary coils when a turn-to-turn short circuit occurs in the motor. Under the turn-to-turn short circuit fault, the voltage drop and equivalent impedance at both ends of the series coils can be automatically guaranteed to remain unchanged, which enables the motor to automatically achieve turn-to-turn short circuit fault tolerance operation. The formula is derived as follows:

[0023] When a turn-to-turn short-circuit fault occurs, the voltage equation of the faulty coil is:

[0024]

[0025] Where e 0_a1 is the induced potential of coil a1, λ is the ratio of short-circuit turns to the total turns of phase A coil, N is the number of coil turns, is the main armature flux component interlinked with coil a1, To compensate for the leakage flux in the leakage magnetic circuit.

[0026] Due to the short circuit,

[0027]

[0028] Substituting into (1), we get

[0029]

[0030] The voltage equation of the unfaulted part is:

[0031]

[0032] Combining equation (3) and equation (4), we get:

[0033]

[0034] It can be seen from equation (5) that the fault causes the voltage of the non-faulty part to drop to 0. However, due to the effect of compensating the leakage magnetic circuit, the voltage equation of the other coil as the faulty coil is:

[0035]

[0036] Where φ m_a2is the main armature flux component interlinked with coil a2, e 0_a2 is the induced potential of coil a2. Add the voltages of the two coils, that is, equation (5) + equation (6), and get the corresponding voltage:

[0037]

[0038] Formula (7) shows that when the motor is under the condition of inter-turn short circuit fault, the leakage flux in the compensation leakage magnetic circuit plays the role of exciting electromotive force and transferring energy, and the mathematical form of the terminal voltage equation of the complementary coil pair including the faulty coil is exactly the same as the mathematical form of the equation under normal working condition; similarly, the mathematical form of the voltage equation of all other complementary coil pairs is the same as that under normal working condition, and will not be repeated; it can be seen that when the power supply remains unchanged, the current of each phase is still almost the same as that under normal working condition, thereby achieving the same torque output as that under normal working condition.

[0039] When a turn-to-turn short circuit occurs, the compensation leakage magnetic circuit not only transfers energy to ensure that the currents of each phase are still symmetrical, but also suppresses the short-circuit current. The high permeability of the compensation leakage magnetic circuit makes the stator coil have a relatively large inductance value, thereby suppressing the short-circuit current. In order to obtain a more ideal fault-tolerant performance, the per-unit value of the reactance value of each stator coil is not less than 2.

[0040] Furthermore, since the distribution coefficient is:

[0041]

[0042] Wherein ν is the harmonic order. It can be seen from the above formula that the electrical angle value of the axial angle α of the two stator teeth included in each pair of stator teeth is 340°~380°, which can ensure that the two effective sides of each coil of the stator winding can be efficiently utilized, so that the motor has a relatively large torque density.

[0043] Adding independent teeth to the stator core can improve the air gap magnetic density of the motor, thereby greatly improving the torque density of the motor. The formula is derived as follows:

[0044] The motor is a permanent magnet synchronous motor with radial magnetic flux and unequal tooth pitch. In order to simplify the calculation, the influence of the arc is ignored and the curved part is regarded as a straight line to establish a mathematical model. First, a mathematical model is established for the permanent magnet. According to the Ampere loop theorem, its surface current density J can be calculated. P (x):

[0045]

[0046] Where b m is the width of the permanent magnet, τ is the pole pitch, B r is the remanence of the permanent magnet, μ0 is the magnetic permeability of vacuum.

[0047] The motor area is divided into 6 parts, such as Figure 7 As shown, region 2 is the stator, region 3 is the air gap, region 4 is the permanent magnet, region 5 is the air gap between the rotor and the permanent magnet (the air gap is very small and can be ignored, so g1 = 0), and region 6 is the rotor. The magnetic flux density of each region can be obtained based on the Poisson equation and the six boundary conditions of the Poisson equation, and the air gap magnetic flux density expression is as follows:

[0048]

[0049] Where B m1y is the expression of radial air gap flux density of the motor, B m1x is the expression of the motor tangential air gap flux density, h m is the thickness of the permanent magnet, and g2 is the air gap length of the motor.

[0050] The air gap flux density obtained above does not consider the influence of the motor stator slots. In practice, the influence of the stator slots on the motor air gap flux density cannot be ignored. Considering the influence of the motor slot effect on the motor magnetic field distribution, taking a single slot model as an example, the specific expression of the relative permeance distribution function in a single slot air gap can be obtained:

[0051] Where b0 is the slot width, b τ is the tooth pitch, g' is the equivalent air gap length.

[0052] The above formula can be used to calculate the magnetic flux density in the radial direction at each position in the motor air gap:

[0053] B y (x,y)=B m1y λ(x,y) (12)

[0054] By calculating the magnetic flux of each phase, it can be verified that independent teeth can significantly improve the torque density of the motor, and the optimal angle of the independent teeth that maximizes the torque density of the motor can be determined.

[0055]

[0056] Φ3=kΦ1 (15)

[0057]

[0058] Where Φ is the total magnetic flux, Φ1 is the main magnetic flux, and Φ2 is the leakage magnetic flux caused by slotting. Figure 8 As shown, Φ3 is the leakage flux between adjacent teeth, and k is the leakage flux coefficient corresponding to the leakage flux between adjacent teeth, which is l is the axial length of the motor, b1 is the top width of the winding teeth, and b0 is the slot width.

[0059] By solving equations (10), (11), (12) and (16) simultaneously, it can be known that when the electrical angle range of the arc length of the tooth top of the independent tooth is not less than 110° and not more than 280°, the increase in the magnetic flux of the motor is not less than 10%, which is beneficial for the motor to have a relatively high torque density.

[0060] In order to make the technical solutions and advantages of the present invention clearer and more complete, the present invention will be described in detail below in conjunction with the accompanying drawings and some specific embodiments. The specific embodiments described here are only used to illustrate the present invention and are not used to limit the present invention.

[0061] Specific embodiment 1: A cross-sectional view of the high torque density turn-to-turn short circuit fault automatic fault-tolerant permanent magnet synchronous motor described in this embodiment is as follows: Figure 1 It is shown that this embodiment is a radial flux, circular rotating motor, including a stator, a rotor and an air gap between the stator and the rotor, and adopts a 6-slot 14-pole pole slot combination. The stator includes a stator core 1 and a stator winding 3, and the rotor includes a permanent magnet 4, a rotor core 2 and a rotating shaft; 14 permanent magnets are evenly distributed on the outer surface of the rotor core, and the N and S polarities of the 14 permanent magnets are alternately arranged along the circumference of the rotor core; the stator core in this embodiment is axially provided with a through slot on one side close to the rotor, forming 6 stator slots and 6 stator teeth; the stator winding is a three-phase winding, and each phase of the stator winding contains two stator coils; the stator core in this embodiment includes 3 magnetic bridges 7; the 3 magnetic bridges are respectively connected to 3 pairs of the stator teeth 5, and an integrated connection is adopted, that is, the magnetic bridges and the The stator core is a whole; each of the magnetic bridges is located at the slot top position of the slot between the two stator teeth connected to it; the electrical angle value of the axis angle of each pair of two stator teeth connected by the magnetic bridge is 360°, and the positions are adjacent. These three pairs of stator teeth are three pairs of stator tooth pairs, so the stator core of this embodiment includes three pairs of stator tooth pairs; the electrical angle value spanned by the tooth top arc length of each stator tooth included in each stator tooth pair is 170°; the stator tooth pairs are evenly distributed along the circumference of the stator core; one stator coil is wound on each of the two stator teeth included in each pair of the stator tooth pairs; the stator coils wound on the two stator teeth included in each pair of the stator tooth pairs have the same winding direction, the same number of turns, belong to the same phase winding, and are connected in series, and the connection method is as follows: Figure 5 shown.

[0062] Specific embodiment 2: The high torque density turn-to-turn short circuit fault automatic fault-tolerant permanent magnet synchronous motor described in this embodiment is as follows: Figure 2As shown, this embodiment is a radial flux, circular rotating motor, including a stator, a rotor and an air gap between the stator and the rotor, adopting a 9-slot 14-pole pole slot combination, the stator includes a stator core 1 and a stator winding, and the rotor includes a permanent magnet, a rotor core and a rotating shaft; 14 permanent magnets are evenly distributed on the outer surface of the rotor core, and the N and S polarities of the 14 permanent magnets are alternately arranged along the circumference of the rotor core; the stator core in this embodiment is axially provided with through slots on one side close to the rotor, forming 9 stator slots and 9 stator teeth; the stator winding is a symmetrical three-phase winding, and each phase of the stator winding contains two stator coils; the stator core in this example includes 3 magnetic bridges 7; the 3 magnetic bridges respectively connect 3 pairs of stator teeth 5, each of the magnetic bridges is located at the slot top position between the two stator teeth it connects, and the electrical angle of the axis of each pair of two stator teeth connected by the magnetic bridge is 1 / 4. The angle value is 360° and the position is adjacent. These three pairs of stator teeth are three pairs of stator tooth pairs. Therefore, the stator core of this embodiment includes three pairs of stator tooth pairs, and the remaining stator teeth are not connected to the magnetic bridge and are called stator independent teeth 6. Therefore, the stator core of this embodiment includes three independent teeth; the electrical angle value spanned by the arc length of the tooth top of each stator tooth included in each stator tooth pair is 170°; the stator tooth pairs are evenly distributed along the circumference of the stator core, and the stator independent teeth are evenly distributed along the circumference of the stator core; the stator independent teeth and the stator tooth pairs are alternately arranged along the circumference of the stator core; one stator coil is wound on each of the two stator teeth included in each pair of the stator tooth pairs; the stator coils wound on the two stator teeth included in each pair of the stator tooth pairs have the same winding direction, the same number of turns, belong to the same phase winding, and are connected in series. The connection method is as follows: Figure 5 As shown; the stator coil is not wound around the independent stator teeth; the electrical angle of the arc length of the tooth top of the independent teeth is 168°.

[0063] Specific embodiment 3: The high torque density turn-to-turn short circuit fault automatic fault-tolerant permanent magnet synchronous motor described in this embodiment is as follows: Figure 3 As shown, this embodiment is based on the specific embodiment 2, and the connection mode between the magnetic bridge 7 and the stator slot is replaced by a splicing connection.

Claims

1. A high torque density turn-to-turn short-circuit fault automatic fault-tolerant permanent magnet synchronous motor, characterized in that: The motor is a circular rotating motor; the motor comprises a stator, a rotor and an air gap therebetween; the stator comprises a stator core (1) and a stator winding; the stator winding is an m-phase winding, m is an integer greater than or equal to 2, each phase of the stator winding comprises 2z stator coils (3), z is an integer greater than or equal to 1; a through slot is axially provided on one side of the stator core close to the rotor to form stator slots and stator teeth; the stator core comprises zm magnetic conductive bridges (7), each magnetic conductive bridge connects two adjacent stator teeth, the number of magnetic conductive bridges connected to each stator tooth does not exceed one, forming zm stator tooth pairs ( 5); the electrical angle value of the axis angle between the two stator teeth included in each stator tooth pair is 340°~380°; the electrical angle value spanned by the tooth top arc length of each stator tooth included in each stator tooth pair is 130°~230°; the stator tooth pairs are evenly distributed along the circumference of the stator core; each of the magnetic bridges is located at the slot top position of the slot between the two stator teeth connected to it; the two stator teeth included in each pair of stator tooth pairs are each wound with a stator coil; the two stator coils wound on the two stator teeth included in each pair of stator tooth pairs have the same number of turns, the same winding direction, belong to the same phase winding, and are connected in series.

2. The high torque density turn-to-turn short-circuit fault automatic fault-tolerant permanent magnet synchronous motor according to claim 1, characterized in that: The per-unit value of the inductance of each stator coil is not less than 2.

3. The high torque density turn-to-turn short-circuit fault automatic fault-tolerant permanent magnet synchronous motor according to claim 1 or 2, characterized in that: The stator core comprises stator teeth not connected to the magnetic bridge, namely independent teeth (6), the number of the independent stator teeth being equal to the number of pairs of stator teeth; the independent stator teeth and the stator tooth pairs being arranged alternately along the circumference of the stator core; and no stator coil is wound around the independent stator teeth.

4. The high torque density turn-to-turn short-circuit fault automatic fault-tolerant permanent magnet synchronous motor according to claim 3, characterized in that: The electrical angle spanned by the arc length of the tooth top of the independent stator teeth is not less than 110° and not more than 280°.

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