In order to weaken the electromagnetic force harmonics caused by the tooth harmonics and effectively suppress the electromagnetic noise of the motor, the analytical formula of radial electromagnetic force wave of step-skew was derived, the mechanism of step-skew suppressing the electromagnetic noise of permanent magnet synchronous motor was analyzed, and the relationship between different segments of step-skew and the order of weakened tooth harmonics was discussed. The radial electromagnetic force wave and electromagnetic noise of a 48-slot 8-pole permanent magnet synchronous motor with different segments of step-skew were simulated and analyzed based on MANATEE simulation platform. The variation of electromagnetic force harmonics with and without step-skew was obtained, and the influence of the step-skew on electromagnetic noise was further analyzed. Results show that when the order of tooth harmonics is integral multiple of segments of step-skew, step-skew cannot weaken the order of tooth harmonics. When the order of tooth harmonics is non-integral multiple of segments, the tooth harmonics and the electromagnetic noise can be effectively suppressed. The measured noise values of the prototype were in good agreement with the simulation results, which verified the mechanism of step-skew suppressing electromagnetic noise of motor and the correctness of the simulation analysis.
Ke XU,Hong-liang YING,Su-rong HUANG,Qi ZHANG. Electromagnetic noise reduction of permanent magnet synchronous motor by step-skewed rotor. Journal of ZheJiang University (Engineering Science), 2019, 53(11): 2248-2254.
Tab.1Characteristic parameters of radial electromagnetic force wave
分类
fr
6f
12f
18f
24f
1
5/?5， 7/7
11/?11， 13/13
17/?17， 19/19
23/?23， 25/25
2
5/7， 5/?17
11/1， 11/?23
17/?5， 17/?29
23/?11
3
7/?5， 7/19
13/1， 13/25
19/7
25/13
4
5/19， 7/?17
11/13， 13/?11
17/7， 19/?5
23/1， 25/1
Tab.2Harmonic sources of 0th electromagnetic force wave of 48-slot 8-pole motor
分类
fr1）
10f
14f
22f
26f
1）注：仅列出与齿谐波相关的径向电磁力谐波来源
1
9/?11， 11/13
13/?11， 15/13
21/?23， 23/25
25/?27， 27/25
2
?
13/1
?
?
3
11/1， 11/25
15/25
23/13
27/17
4
9/13， 11/?11
13/13， 15/?11
21/1
25/1
Tab.3Harmonic sources of 8th electromagnetic force wave of 48-slot 8-pole motor
参数
数值
定子槽数
48
极数
8
最大转速/（r·min?1）
9 500
额定转速/（r·min?1）
4 000
最大扭矩/（N·m）
200
机壳外径/mm
270
电机轴向长度/mm
105
转子分段数
2
转子斜极角度/(°)
3.75
Tab.4Technical parameters of prototype
Fig.1No-load air gap magnetic density simulation results in different segment numbers
Fig.2Harmonic analysis of radial electromagnetic force in different segment numbers
Fig.3A-weighted sound pressure level sonagram at full speed conditions
Fig.4A-weighted sound level comparison in different segment numbers of step-skewed rotor
Fig.5Noise test experiment of prototype
n0/（r·min?1）
Lp-test/dB
Lp/dB
2 500
55.9
53.2
4 000
60.5
59.2
5 500
56.6
51.2
7 000
63.7
58.1
8 500
69.3
65.9
9 500
66.7
63.3
Tab.5Comparison between measured noise values and simulation results
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