Dual armature flux switching electric excitation motor

Abstract

The present invention relates to a dual armature flux switching electric excitation motor, including a stator and a rotor, wherein the stator includes a stator core, an excitation winding and a stator armature winding, the stator core has stator slots distributed along its circumference, the stator slots include a first stator slot and a second stator slot, the first stator slot is provided on both sides with a second stator slot, the first stator slot is used to accommodate the excitation winding, and the second stator slot is used to accommodate the stator armature winding; the rotor includes a rotor core and a rotor armature winding, the rotor core includes rotor slots distributed along its circumference, and the rotor slots are used to accommodate the rotor armature winding; when each winding is in a working state, the excitation winding is passed through direct current, the stator armature winding and the rotor armature winding are passed through alternating current, the phase angle of the stator armature winding current is controlled to be 0° to 90°, and the phase angle of the rotor armature winding current is controlled to be ‑90° to 0°. The present invention realizes a significant improvement in the torque density of the electric excitation motor through the dual armature topology and the phase angle coordination of each armature winding current.

Description

Technical Field

[0001] The invention belongs to the technical field of motors, and in particular relates to a dual-armature flux switching electric excitation motor. Background Art

[0002] Flux switching permanent magnet motors are a popular type of stator permanent magnet motors in recent years. Compared with traditional surface-mounted permanent magnet motors, they have comparable torque density, stronger anti-demagnetization ability, better speed regulation performance, and simple rotor structure. However, this type of motor requires a large amount of permanent magnets, which limits the further expansion of its application in today's rare earth eradication context.

[0003] In response to the above problems, many scholars have considered using electric excitation and hybrid excitation to reduce the amount of permanent magnets in this type of motor. For example, JT Chen, ZQ Zhu and others from the University of Sheffield in the UK proposed in their paper that under the original flux switching topology, excitation windings can be used to replace permanent magnets (Low cost flux-switching brushless ACmachines, IEEE Vehicle Power and Propulsion Conference, 2010) to achieve lower costs. Compared with similar permanent magnet motors, the electric excitation solution has the advantages of no demagnetization risk, a wider speed regulation range, and a more flexible speed regulation strategy. In addition, the integral stator structure is much easier to process and assemble than the block core structure in the permanent magnet solution. Therefore, the flux switching electric excitation motor has strong application potential in some special scenarios.

[0004] The main disadvantages of conventional flux switching electric excitation motors are as follows:

[0005] First, flux-switching electric excitation motors usually use DC excitation windings to provide a constant magnetic field, which is equivalent to the function of permanent magnets in permanent magnet motors. However, the magnetic field generated by the DC excitation current is usually much weaker than the magnetic field provided by NdFeB permanent magnets, which is also the fundamental reason for the low torque density of flux-switching electric excitation motors. Although increasing the excitation current or the number of turns of the excitation coil can strengthen the magnetic field, this will significantly increase the electrical and thermal loads of the motor, which will bring great difficulties to the insulation design and cooling management of the motor.

[0006] Second, the flux-switching electric excitation motor only has stator excitation winding and stator armature winding, and its fault tolerance is weak. Once either the excitation winding or the armature winding fails, the motor will not be able to output torque. Although they are all designed in multiple sets, for example, the armature winding is separated into two or more sets of independent control windings according to the spatial distribution, which can guarantee a certain degree of fault-tolerant operation performance, this will lead to a serious decline in performance indicators such as motor torque output, efficiency, and operation stability, and it is very likely to produce unbalanced forces, increased local eddy current losses, and many other parasitic negative effects. In addition, multiple sets of independently controlled windings mean that the corresponding inverter hardware cost increases and the control logic becomes more complicated. Summary of the invention

[0007] Based on the above-mentioned shortcomings and deficiencies in the prior art, one of the objects of the present invention is to at least solve one or more of the above-mentioned problems in the prior art. In other words, one of the objects of the present invention is to provide a dual-armature flux switching electromagnetic excitation motor that meets one or more of the above-mentioned requirements.

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0009] A dual-armature flux switching electric excitation motor comprises a stator and a rotor, wherein the stator comprises a stator core, an excitation winding and a stator armature winding, the stator core has stator slots distributed along its circumference, the stator slots comprise a first stator slot and a second stator slot, the first stator slot is provided with a second stator slot on both sides, the first stator slot is used to accommodate the excitation winding, and the second stator slot is used to accommodate the stator armature winding;

[0010] The rotor comprises a rotor core and a rotor armature winding, wherein the rotor core comprises rotor slots distributed along its circumference, and the rotor slots are used to accommodate the rotor armature winding;

[0011] When each winding is in working state, direct current is passed through the excitation winding, and alternating current is passed through the stator armature winding and the rotor armature winding. The phase angle of the stator armature winding current is controlled to be 0°~90°, and the phase angle of the rotor armature winding current is controlled to be -90°~0°.

[0012] As a preferred solution, the phase angle of the stator armature winding current is controlled to be 0° to 20°, and the phase angle of the rotor armature winding current is controlled to be -60° to -30°.

[0013] As a preferred solution, the difference between the phase angle of the stator armature winding current and the phase angle of the rotor armature current is controlled to be 40° to 70°.

[0014] As a preferred solution, the first stator slots are parallel slots, the second stator slots are non-parallel slots, and the area of ​​the first stator slots is greater than the area of ​​the second stator slots.

[0015] As a preferred solution, the copper loss of the excitation winding is greater than the copper loss of the stator armature winding, and the copper loss of the rotor armature winding is greater than the copper loss of the stator armature winding.

[0016] As a preferred solution, the copper loss of the excitation winding is equal to the copper loss of the rotor armature winding.

[0017] As a preferred solution, adjacent stator slots are separated by stator teeth, and the stator teeth are parallel teeth with the same width;

[0018] The slot width of the first stator slot is greater than the tooth width of the stator tooth, and the tooth width of the stator tooth is greater than the maximum yoke thickness of the stator core.

[0019] As a preferred solution, the slot width of the first stator slot is greater than the maximum slot width of the second stator slot, and the slot width of the second stator slot is smaller than the tooth width of the stator tooth.

[0020] As a preferred solution, the slot depth of the first stator slot is greater than the slot depth of the second stator slot.

[0021] As a preferred solution, adjacent rotor slots are separated by rotor teeth, and the rotor teeth are parallel teeth;

[0022] The tooth tip width of the rotor tooth is greater than the slot width of the first stator slot.

[0023] As a preferred solution, when the rotor armature winding is disconnected and the excitation winding and the stator armature winding are working, the phase angle of the stator armature winding current is controlled to be 0°;

[0024] When the stator armature winding is disconnected and the field winding and the rotor armature winding are working, the phase angle of the rotor armature winding current is controlled to 0°;

[0025] When the excitation winding is disconnected and the stator armature winding and the rotor armature winding are working, the phase angle of the stator armature winding current is controlled to be 0°~20°, the phase angle of the rotor armature winding current is controlled to be -60°~-30°, and the difference between the phase angle of the stator armature winding current and the phase angle of the rotor armature current is controlled to be 40°~70°.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention can significantly improve the torque density of the flux-switching electric excitation motor through the dual armature topology and the phase angle coordination of each armature winding current. On this basis, the torque density can be further improved by relying on the phase angle of each winding current, the copper loss distribution of each winding, and the mutual coordination of the special stator slot type. Compared with the traditional flux-switching electric excitation motor, the copper loss generated by the motor is distributed on both sides of the stator and rotor. When the stator and rotor are equipped with active cooling at the same time, a lower temperature rise and more uniform temperature distribution will be obtained.

[0028] The dual-armature flux switching electric excitation motor of the present invention has excellent fault-tolerant performance, which is mainly reflected in two aspects: first, there is no need for winding set processing and winding category switching. Even if the excitation winding fails, the motor can still operate, ensuring the simplicity and economy of the system structure, and the fault-tolerant control logic is also relatively simple; second, in any fault-tolerant operation mode, without changing the current amplitude, a considerable part of the torque output can still be guaranteed, and no negative effects such as extremely unbalanced radial force and significantly increased torque fluctuations will be generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the topological structure of the dual-armature flux switching electric excitation motor according to Embodiment 1 of the present invention;

[0030] Figure 2 It is a schematic diagram of the stator armature winding and the rotor armature winding of the dual armature flux switching electric excitation motor according to embodiment 1 of the present invention. DETAILED DESCRIPTION

[0031] In order to more clearly illustrate the embodiments of the present invention, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other accompanying drawings and other implementation methods can be obtained based on these accompanying drawings without creative work.

[0032] Embodiment 1:

[0033] like Figure 1 As shown, the dual-armature flux switching electric excitation motor of this embodiment is an outer stator and inner rotor structure, specifically including a stator and a rotor, the stator including a stator core 11 with a slot structure, an excitation winding 12, and a stator armature winding 13, and the rotor including a rotor core 21 with a slot structure and a rotor armature winding 22.

[0034] The stator core 11 of the present embodiment has twenty-four stator slots distributed along its circumference. The types of stator slots include first stator slots 111 and second stator slots 112. The number of first stator slots 111 for accommodating the excitation winding 12 is twelve, and the number of second stator slots 112 for accommodating the stator armature winding 13 is twelve, and the first stator slots 111 and the second stator slots 112 are alternately distributed along the circumference. For all stator slots, the excitation winding 12 is a single-layer distributed winding, and the stator armature winding 13 is a double-layer distributed winding, and the span of both is two, which minimizes the end length. The six excitation windings correspond to six pairs of poles, and the twelve stator armature coils are divided into three phases. The specific phase division is as follows: Figure 2 As shown, it is divided into phase A, phase B and phase C cyclically along the circumferential direction.

[0035] The rotor core 21 of this embodiment has ten rotor slots 210, all of which are used to accommodate the rotor armature winding 22. The rotor armature winding 22 is a double-layer concentrated winding, and the ten rotor armature windings are divided into five phases. Figure 2 As shown, the phases circulating along the circumferential direction are divided into phase A, phase D, phase B, phase E and phase C.

[0036] In this embodiment, adjacent stator slots are separated by stator teeth 113, and adjacent rotor slots are separated by rotor teeth 211. Both the stator teeth 113 and the rotor teeth 211 are parallel teeth, and the tooth widths of all stator teeth are equal, and the tooth widths of all rotor teeth are equal, and the tooth width of the stator teeth 113 is greater than the thickness of the stator core yoke 114.

[0037] In this embodiment, the first stator slot 111 is a parallel slot, the second stator slot 112 is a trapezoidal slot, and the rotor slots 210 are all trapezoidal slots. The slot area of ​​the first stator slot 111 is greater than the slot area of ​​the second stator slot 112, and the slot width of the first stator slot 111 is greater than the maximum slot width of the second stator slot 112, that is, the slot bottom width of the second stator slot 112, and the slot width of the second stator slot 112 is less than the tooth width of the stator tooth 113. In addition, the tooth width of the rotor tooth 211 of this embodiment is slightly greater than the slot width of the first stator slot 111, and this structure is conducive to achieving a more sinusoidal back electromotive force and a smaller cogging torque.

[0038] As far as the stator winding process is concerned, relatively large parallel slots are convenient for winding, and even formed coils can be installed radially. When winding, the armature coil with a smaller size corresponding to the stator slot can be wound first, and then the excitation coil can be wound or installed. The lead-out armature winding end can be arranged along the stator core yoke, and the excitation winding end can bypass the stator teeth and the armature winding end, so as to facilitate the overlap of the armature coil and the excitation coil.

[0039] When the motor is in normal operation, the field winding, stator armature winding, and rotor armature winding are in working state, the field winding is energized by direct current, and the stator armature winding and the rotor armature winding are energized by alternating current. In order to maximize the torque when the total copper loss is fixed, the following copper loss distribution relationship is maintained under the premise that all stator slots and rotor slots have the same slot full rate: the copper loss of the field winding is greater than the copper loss of the stator armature winding, and the copper loss of the rotor armature winding is greater than the copper loss of the stator armature winding; preferably, the copper loss of the field winding is equal to the copper loss of the rotor armature winding, or the two are similar. When the motor is operating normally, the phase angle of the stator armature winding current (referred to as the stator current phase angle) is controlled to 0°~90°, and the phase angle of the rotor armature winding current (referred to as the rotor current phase angle) is controlled to -90°~0°, so as to achieve maximum torque output. Preferably, the phase angle of the rotor armature winding current is controlled to be -30° to -60°, and the phase angle of the stator armature winding current is controlled to be 0° to 20°, so as to achieve a larger torque. Preferably, the difference between the phase angle of the stator armature winding current and the phase angle of the rotor armature current is controlled to be 40° to 70°. The phase angle is generally defined as the angle between the AC current and the corresponding back-EMF phase, and a positive value indicates that the current leads the back-EMF.

[0040] In order to achieve the maximum torque in fault-tolerant operation mode, the armature current control is different from normal operation and includes the following three modes:

[0041] The first mode: when the rotor armature winding is disconnected and the field winding is working with the stator armature winding, the phase angle of the stator armature winding current is controlled to 0°;

[0042] The second mode: when the stator armature winding is disconnected and the excitation winding and the rotor armature winding are working, the phase angle of the rotor armature winding current is controlled to 0°;

[0043] The control method of the phase angle control being 0° is the simplest, and can achieve output close to the maximum torque in the above two modes;

[0044] The third mode: when the excitation winding is disconnected and the stator armature winding and the rotor armature winding are working, the phase angles of the stator armature winding current and the rotor armature current are kept the same as those in normal operation, that is, the current phase angle of the stator armature winding is controlled to be 0°~20°, the phase angle of the rotor armature winding current is controlled to be -60°~-30°, and the difference between the phase angle of the stator armature winding current and the phase angle of the rotor armature current is controlled to be 40°~70°;

[0045] In the above three modes, there is no need to adjust the type and amplitude of the current. Just by adjusting the phase angle of the current, a considerable partial torque output can be maintained. In addition, the special stator slot type, copper loss distribution of each set of windings, and the phase angle of each set of winding currents mentioned above are necessary conditions for maximizing torque and must cooperate with each other. For normal operation:

[0046] (1) Allocate relatively more copper loss to the rotor armature winding and relatively less copper loss to the stator armature winding. This is because the rotor part generates more torque per unit copper loss. However, if too much copper loss is allocated to the rotor armature winding, the torque cannot be maximized.

[0047] (2) In addition to the stator armature copper loss and the rotor armature copper loss, a large part of the copper loss is allocated to the excitation winding, which means that the torque value generated under its unit copper loss is also large. Therefore, a relatively large accommodation space needs to be allocated to the excitation winding, so the slot area of ​​the first stator slot is set to be larger than the slot area of ​​the second stator slot. On this basis, the first stator slot is further designed as a parallel slot, which can effectively avoid the leakage of magnetic flux in the slot after the excitation current is increased. According to relevant research and analysis, the leakage of magnetic flux in the slot is one of the main reasons why the performance of the flux switching electric excitation motor is inferior to that of similar permanent magnet motors, which is particularly prominent under high current conditions;

[0048] (3) After the phase angle of the rotor armature winding current is controlled at -90° to 0°, the torque generated by the rotor armature winding and the excitation winding will decrease, but it can also interact with the stator armature winding to generate torque, and this part is significantly improved. Therefore, compared with the case where the phase angle of the rotor armature winding current is controlled to 0°, it has obvious advantages. This is also a unique feature of this type of motor.

[0049] Table 1 Specific structural parameters and copper loss information of dual armature flux switching electric excitation motor

[0050]

[0051] As an example, the specific structural parameters and copper loss information of the dual armature flux switching electric excitation motor of this embodiment are shown in Table 1. Based on the above motor structure, the total copper loss is defined as 80W. When calculating the copper loss, the slot full rate of all slots is defined as 40%, which is consistent, and the end length of all coils is also taken into account for resistance calculation. The ratio of the copper loss of the excitation winding, the copper loss of the stator armature winding, and the copper loss of the rotor armature winding is set to 3:2:3 to maximize the torque density under the condition of fixed total copper loss. Even when the phase angles of the stator armature winding and the rotor armature winding are simply controlled to 0°, this ratio is also a prerequisite for achieving maximum torque. At this time, the torque of the dual armature flux switching electric excitation motor can reach 0.99Nm, while the torque of the optimized traditional flux switching electric excitation motor (i.e., comparative example 1) is only 0.68Nm. The specific calculation result data is shown in Table 2.

[0052] Table 2 Comparison of motor torque between Example 1 and Comparative Example 1

[0053]

[0054] As shown in Table 2, the phase angle of the dual armature flux switching electric excitation motor is further adjusted. When the stator current phase angle is controlled to 10° and the rotor current phase angle is controlled to -35°, the torque is further increased to 1.20Nm. This is because the torque generated by the stator armature winding and the rotor armature winding is generated by the stator on the rotor. The salient pole effect is a factor that must be considered in the dual armature flux switching electric excitation motor, but it is greatly affected by the magnetic circuit structure. The salient pole torque values ​​and the corresponding optimal rotor current phase angles of different motors and structures are very different. On the other hand, the torque generated by the interaction between the stator and rotor armatures without considering the cogging effect reaches the maximum when the difference between the phase angles of the two is 90°. Considering the two torque components comprehensively, in this example, the difference between the phase angles of the two is optimal when it reaches 45°. For different motors, the difference between the phase angles of the two is too close to 0° or 90°, which indicates that the salient pole structure is not reasonably designed.

[0055] It should be pointed out that if the slot types of the first stator slot and the second stator slot are interchanged, and the areas of the two are kept unchanged, and the other structural parameters and copper loss information remain unchanged, the torque will drop from 1.20Nm to 1.00Nm. This result shows that the first stator slot is a parallel slot and the second stator slot is a non-parallel slot, which plays an extremely important role in maximizing the torque output.

[0056] For the case where any type of winding fails and is disconnected, the fault-tolerant operation results are shown in Table 3. Obviously, the traditional flux switching electric excitation motor cannot provide the possibility of fault-tolerant operation in this case. In contrast, the dual-armature flux switching electric excitation motor still has the ability to operate fault-tolerantly after any type of winding fails. Without changing the current amplitude (at most changing the current phase angle), the torque can still be output in all three cases.

[0057] Table 3 Comparison of fault-tolerant operation results of the motors of Example 1 and Comparative Example 1

[0058]

[0059] When the stator armature winding is disconnected, the maximum torque is 0.71Nm, which is 59% of the normal operation, and the phase angle needs to be reasonably adjusted to achieve it; on the contrary, if a simple rotor current phase angle control of 0° is adopted, the output torque is 0.66Nm, which is a slight decrease, but the advantage is that the control strategy is relatively simple.

[0060] When the rotor armature winding is disconnected, the maximum torque is 0.35Nm, which is 29% of the normal operation, and only the stator current phase angle needs to be controlled to 0°.

[0061] When the excitation winding is disconnected, keeping the stator current phase angle and the rotor current phase angle the same as normal, that is, the stator current phase angle is controlled to 10° and the rotor current phase angle is controlled to -35°, can ensure the maximum torque output in this case, which is 0.41Nm, which is 34% of the normal operation.

[0062] In summary, the dual-armature flux switching electric excitation motor of the present invention has higher torque density and better fault tolerance.

[0063] Embodiment 2:

[0064] The dual armature flux switching electric excitation motor of this embodiment is different from that of Embodiment 1 in that:

[0065] The rotor teeth are provided with a tooth tip structure on one or both sides. The tooth tip structure and its size have little effect on the torque, but can further reduce the cogging torque. In this case, the tip width of the rotor teeth should be slightly larger than the slot width of the first stator slot.

[0066] For other structures, please refer to Example 1.

[0067] Embodiment 3:

[0068] The dual armature flux switching electric excitation motor of this embodiment is different from that of Embodiment 1 in that:

[0069] The number of the first stator slots and the number of the second stator slots may be different to accommodate the possibility of different pole slot combinations, but the first stator slot must be surrounded by the second stator slots on both sides.

[0070] Specific other pole slot combinations and structures can be deformed or expanded on the basis of reference embodiment 1.

[0071] The above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, according to the ideas provided by the present invention, there will be changes in the specific implementation methods, and these changes should also be regarded as the protection scope of the present invention.

Claims

1. A dual-armature flux switching electric excitation motor, comprising a stator and a rotor, characterized in that: The stator comprises a stator core, an excitation winding and a stator armature winding, the stator core has stator slots distributed along its circumference, the stator slots comprise a first stator slot and a second stator slot, both sides of the first stator slot are second stator slots, the first stator slot is used to accommodate the excitation winding, and the second stator slot is used to accommodate the stator armature winding; The rotor comprises a rotor core and a rotor armature winding, wherein the rotor core comprises rotor slots distributed along its circumference, and the rotor slots are used to accommodate the rotor armature winding; When each winding is in working state, direct current is passed through the excitation winding, and alternating current is passed through the stator armature winding and the rotor armature winding. The phase angle of the stator armature winding current is controlled to be 0°~90°, and the phase angle of the rotor armature winding current is controlled to be -90°~0°.

2. The dual armature flux switching electric excitation motor according to claim 1, characterized in that: The phase angle of the stator armature winding current is controlled to be 0° to 20°, and the phase angle of the rotor armature winding current is controlled to be -60° to -30°.

3. The dual armature flux switching electric excitation motor according to claim 2, characterized in that: The difference between the phase angle of the stator armature winding current and the phase angle of the rotor armature current is controlled to be 40° to 70°.

4. The dual armature flux switching electric excitation motor according to any one of claims 1 to 3, characterized in that: The first stator slot is a parallel slot, the second stator slot is a non-parallel slot, and the area of ​​the first stator slot is greater than the area of ​​the second stator slot.

5. The dual armature flux switching electric excitation motor according to claim 4, characterized in that: The copper loss of the excitation winding is greater than the copper loss of the stator armature winding, and the copper loss of the rotor armature winding is greater than the copper loss of the stator armature winding.

6. The dual armature flux switching electric excitation motor according to claim 5, characterized in that: The copper loss of the excitation winding is equal to the copper loss of the rotor armature winding.

7. The dual armature flux switching electric excitation motor according to claim 5, characterized in that: Adjacent stator slots are separated by stator teeth, and the stator teeth are parallel teeth with the same width; The slot width of the first stator slot is greater than the tooth width of the stator tooth, and the tooth width of the stator tooth is greater than the maximum yoke thickness of the stator core.

8. The dual armature flux switching electric excitation motor according to claim 7, characterized in that: The slot width of the first stator slot is greater than the maximum slot width of the second stator slot, and the slot width of the second stator slot is less than the tooth width of the stator tooth.

9. The dual armature flux switching electric excitation motor according to claim 4, characterized in that: Adjacent rotor slots are separated by rotor teeth, which are parallel teeth; The tooth tip width of the rotor tooth is greater than the slot width of the first stator slot.

10. The dual armature flux switching electric excitation motor according to any one of claims 1 to 3, characterized in that: When the rotor armature winding is disconnected and the field winding and the stator armature winding are working, the phase angle of the stator armature winding current is controlled to 0°; When the stator armature winding is disconnected and the field winding and the rotor armature winding are working, the phase angle of the rotor armature winding current is controlled to 0°; When the excitation winding is disconnected and the stator armature winding and the rotor armature winding are working, the phase angle of the stator armature winding current is controlled to be 0°~20°, the phase angle of the rotor armature winding current is controlled to be -60°~-30°, and the difference between the phase angle of the stator armature winding current and the phase angle of the rotor armature current is controlled to be 40°~70°.

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