A skew-pole permanent magnet motor rotor and its design method

Abstract

The present invention discloses a skewed-pole permanent magnet motor rotor and a design method thereof. The rotor includes a motor shaft and several sections of rotor cores arranged in a skewed pole arrangement, which are sleeved on the motor shaft. Adjacent sections of the rotor cores have different lengths, and each section of the rotor core is equipped with a permanent magnet. First, the total skew angle of the skewed-pole permanent magnet motor rotor, which is configured with N sections of rotor cores of equal length in the original scheme, is determined. Finite element simulation software is used to determine the motor torque and torque pulsation values of the original scheme. The total skew angle of the new skewed-pole permanent magnet motor rotor remains unchanged. A binary method combined with finite element simulation software is used to optimize the angle between the centerlines of the magnetic poles of each adjacent section of the rotor core. The skewed-pole permanent magnet motor rotor proposed in the present invention can be designed with permanent magnets of different specifications to achieve the same output torque capacity as permanent magnets of the same specification. An algorithm is also used to reduce motor torque pulsation, improve motor stability, and reduce vibration noise.

Description

Technical Field

[0001] The present invention relates to the field of permanent magnet motors, and in particular to a skew-pole permanent magnet motor rotor and a design method thereof. Background Art

[0002] Torque fluctuation is an important indicator affecting the performance of permanent magnet motors. Torque fluctuation can cause motor jitter, generate electromagnetic vibration and noise, and affect control accuracy. Severe fluctuations can lead to performance degradation or even control failure.

[0003] In order to reduce torque fluctuations, existing new energy permanent magnet motors often use a rotor skew method, which divides the motor rotor axially into several segments. The center lines of the magnetic poles of each segment differ by a certain angle in the circumferential direction. The total skew angle = tooth pitch angle × (number of segments - 1) / number of segments.

[0004] However, the segmented skew-pole rotors used in existing permanent magnet motors require that the permanent magnet materials have uniform size specifications. A single product uses a single specification of permanent magnet, and the permanent magnet materials cannot be used interchangeably between different motors with the same punching structure. Summary of the Invention

[0005] The purpose of the present invention is to provide a skew-pole permanent magnet motor rotor that can be combined using rotor cores of different lengths, and to optimize the motor's skew angle using an algorithm, thereby improving the motor's stability and vibration noise by reducing the motor's torque pulsation.

[0006] The technical solution of the present invention is:

[0007] A skewed pole permanent magnet motor rotor comprises a motor shaft and several sections of rotor cores with skewed poles sleeved on the motor shaft. Adjacent sections of the rotor cores have different lengths, and each section of the rotor core is equipped with a permanent magnet of the same length as the rotor core.

[0008] Preferably, the length of each section of the rotor core gradually increases from the two ends to the middle of the motor shaft.

[0009] Preferably, in each section of the rotor core, the left and right sections of the rotor core that are at the same distance from the center of the motor shaft have the same length.

[0010] Preferably, the lengths of the various sections of the rotor core increase in equal proportion or arithmetic progression from the two ends to the middle of the motor shaft.

[0011] Preferably, each section of the rotor core is composed of a number of rotor punchings of the same size with 8 poles and 48 slots.

[0012] A method for designing a skew-pole permanent magnet motor rotor, comprising:

[0013] S1. First, determine the original solution of the skew-pole permanent magnet motor rotor:

[0014] The original skew-pole permanent magnet motor rotor is equipped with N equal-length rotor cores, with M winding slots. The original rotor's total skew angle α = (360° / M) * (N-1) / N, and the angle β between the center lines of the magnetic poles of two adjacent rotor cores is (360° / M) / N.

[0015] S2. Using finite element simulation software, simulate the motor parameters of the original skew-pole permanent magnet motor rotor to determine the motor torque T and torque ripple value S of the original solution;

[0016] S3. Design a new skew-pole permanent magnet motor rotor:

[0017] The new skew-pole permanent magnet motor rotor is equipped with the rotor core described in Section N'. The number of winding slots on the rotor core remains M. The new rotor total skew angle α' is the same as the original rotor total skew angle α, that is, α'=α.

[0018] S4. For the new skew-pole permanent magnet motor rotor, use the bisection method combined with finite element simulation software to optimize the angle β' between the centerlines of the magnetic poles of each adjacent rotor core segment. Monitor the new motor torque T' and torque ripple value S' until the new motor torque T' is within ±2% of the original solution's motor torque T and the new torque ripple value S' is lower than the original solution's torque ripple value S.

[0019] The advantages of the present invention are:

[0020] The skewed-pole permanent magnet motor rotor proposed in the present invention can use permanent magnets of different specifications for motor design, achieving the same output torque capacity as permanent magnets of the same specifications, and using algorithms to reduce motor torque pulsation, improve motor stability and reduce vibration noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0022] Figure 1 Schematic diagram of the structure of the skew-pole permanent magnet motor rotor A in the embodiment;

[0023] Figure 2 Schematic diagram of a permanent magnet motor rotor punching sheet used in the embodiment;

[0024] Figure 3 A comparison diagram of the skew-pole permanent magnet motor rotors A and B in the embodiment;

[0025] Figure 4 2. A comparison diagram of the permanent magnet structures used in the skew-pole permanent magnet motor rotors A and B in the embodiment;

[0026] Figure 5 Schematic diagram of the skewed pole segments of the skewed pole permanent magnet motor rotor A in the embodiment;

[0027] Figure 6 : is a simulation parameter diagram of the skew-pole permanent magnet motor rotor A in the embodiment;

[0028] Figure 7 Schematic diagram of the skewed pole segments of the skewed pole permanent magnet motor rotor C in the embodiment;

[0029] Figure 8 3 is a simulation parameter diagram of the skew-pole permanent magnet motor rotor C in the embodiment. DETAILED DESCRIPTION

[0030] The structure of the permanent magnet motor rotor of new energy vehicles usually includes the motor shaft, rotor core and permanent magnets.

[0031] like Figure 1 and 3 Figure 2 shows two conventional skewed-pole permanent magnet motor rotors A and B of different lengths. Both rotors A and B comprise a motor shaft 1 and four rotor cores 2 arranged in a skewed arrangement, sleeved around the motor shaft 1. Adjacent rotor cores 2 have the same length. The lengths of rotors A and B are 80 mm and 160 mm, respectively. The lengths of the single-segment rotor cores 2 on rotors A and B are 20 mm and 40 mm, respectively.

[0032] like Figure 2 As shown, each section of the rotor core 2 of the skew-pole permanent magnet motor rotors A and B is composed of a number of rotor punchings 2 - 1 of the same size with 8 poles and 48 slots.

[0033] like Figure 4 As shown, each rotor core 2 of the skew-pole permanent magnet motor rotors A and B is equipped with a first permanent magnet 3 and a second permanent magnet 3' of the same length as the rotor core 2, that is, the lengths of the two types of permanent magnets are 20 mm and 40 mm respectively.

[0034] This embodiment proposes a new skewed-pole permanent magnet motor rotor C based on the above two skewed-pole permanent magnet motor rotors. The specific design steps are as follows:

[0035] S1, such as Figure 5 As shown, since the number of segments of the permanent magnet motor rotor A is N=4, the total rotor skew angle α= (360° / 48)*(N-1) / N=5.625°, and the angle β between the center lines of two adjacent magnetic pole segments centered on the motor shaft is (360° / 48) / N=1.875°.

[0036] S2, such as Figure 6 As shown, using common finite element simulation software, the motor parameters of the permanent magnet motor rotor A are first simulated to determine the motor torque T and torque pulsation value S of the original scheme.

[0037] S3, such as Figure 7 As shown in the figure, the rotor core and permanent magnet specifications of the skewed-pole permanent magnet motor rotors A and B are selected for matching design to construct a new skewed-pole permanent magnet motor rotor C. The number of segments of the rotor core of the skewed-pole permanent magnet motor rotor C is N=3, and the lengths of the three rotor core segments are 20 mm, 40 mm, and 20 mm, respectively.

[0038] S4, such as Figure 8 As shown in the figure, the new total rotor skew angle α' is kept unchanged at 5.625°, and the angle β' between the center lines of the magnetic poles of the rotor core of each adjacent segment is optimized by using the bisection method combined with finite element simulation software. The new motor torque T' and torque ripple value S' are monitored until the new motor torque T' differs from the motor torque T of the original solution within ±2%, and the new torque ripple value S' is lower than the torque ripple value S of the original solution.

[0039] In this embodiment, the angles β' separating the centerlines of the magnetic poles of adjacent rotor core segments are -2.8125°, 1°, and 2.8125°. Simulation data show that torque ripple decreases by 7.8% while torque decreases by 0.6%. The use of permanent magnet motor rotor C achieves the goal of reducing torque ripple and improving motor performance.

[0040] In addition to the above embodiments, motors of different specifications can be designed with skewed poles using the same method, for example, increasing the number of skewed pole segments. However, it is best to design according to the following principles to reduce optimization difficulty.

[0041] (1) The length of each section of the rotor core 2 gradually increases from the two ends to the middle of the motor shaft 1.

[0042] (2) In each section of the rotor core 2, the left and right sections of the rotor core 2 that are at the same distance from the center of the motor shaft 1 are of equal length.

[0043] (3) The lengths of the various sections of the rotor core 2 increase in equal proportion or asymptotically from the two ends to the middle of the motor shaft 1.

[0044] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any modifications made based on the spirit of the main technical solution of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A skew-pole permanent magnet motor rotor, characterized in that: The invention comprises a motor shaft (1) and a plurality of rotor cores (2) with oblique poles arranged on the motor shaft (1), wherein adjacent rotor cores (2) have different lengths, and each rotor core (2) is equipped with a permanent magnet (3) having the same length as the rotor core (2); The design method of the skew-pole permanent magnet motor rotor includes: S1. First, determine the original solution of the skew-pole permanent magnet motor rotor: The original skew-pole permanent magnet motor rotor is equipped with N equal-length rotor cores, with M winding slots. The original rotor's total skew angle α = (360° / M) * (N-1) / N, and the angle β between the center lines of the magnetic poles of two adjacent rotor cores is (360° / M) / N. S2. Using finite element simulation software, simulate the motor parameters of the original skew-pole permanent magnet motor rotor to determine the motor torque T and torque ripple value S of the original solution; S3. Design a new skew-pole permanent magnet motor rotor: The new skew-pole permanent magnet motor rotor is equipped with N' segments of rotor core, and the number of winding slots on the rotor core is still M. The new rotor total skew angle α' is the same as the original rotor total skew angle α, that is, α'=α; S4. For the new skew-pole permanent magnet motor rotor, use the bisection method combined with finite element simulation software to optimize the angle β' between the centerlines of the magnetic poles of each adjacent rotor core segment. Monitor the new motor torque T' and torque ripple value S' until the new motor torque T' is within ±2% of the original solution's motor torque T and the new torque ripple value S' is lower than the original solution's torque ripple value S.

2. The skew-pole permanent magnet motor rotor according to claim 1, characterized in that: The lengths of the various sections of the rotor core (2) gradually increase from the two ends to the middle of the motor shaft (1).

3. The skew-pole permanent magnet motor rotor according to claim 2, characterized in that: In each section of the rotor core (2), the left and right sections of the rotor core (2) at the same distance from the center of the motor shaft (1) are of equal length.

4. The skew-pole permanent magnet motor rotor according to claim 3, characterized in that: The lengths of the various sections of the rotor core (2) increase in equal proportion or arithmetic progression from the two ends to the middle of the motor shaft (1).

5. The skew-pole permanent magnet motor rotor according to claim 4, characterized in that: Each section of the rotor core (2) is composed of a plurality of rotor punchings (2-1) of the same size with 8 poles and 48 slots.

6. A design method for a skew-pole permanent magnet motor rotor, characterized in that: include: S1. First, determine the original solution of the skew-pole permanent magnet motor rotor: The original skew-pole permanent magnet motor rotor is equipped with N equal-length rotor cores, with M winding slots. The original rotor's total skew angle α = (360° / M) * (N-1) / N, and the angle β between the center lines of the magnetic poles of two adjacent rotor cores is (360° / M) / N. S2. Using finite element simulation software, simulate the motor parameters of the original skew-pole permanent magnet motor rotor to determine the motor torque T and torque ripple value S of the original solution; S3. Design a new skew-pole permanent magnet motor rotor: The new skew-pole permanent magnet motor rotor is provided with N' segments of the rotor core according to any one of claims 1 to 5, the number of winding slots on the rotor core is still M, and the new rotor total skew angle α' is the same as the original rotor total skew angle α, that is, α'=α; S4. For the new skew-pole permanent magnet motor rotor, use the bisection method combined with finite element simulation software to optimize the angle β' between the centerlines of the magnetic poles of each adjacent rotor core segment. Monitor the new motor torque T' and torque ripple value S' until the new motor torque T' is within ±2% of the original solution's motor torque T and the new torque ripple value S' is lower than the original solution's torque ripple value S.

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