Analysis of Harmonic Current in Permanent Magnet Synchronous Motor and Its Effec.docx
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1、ScientificResearchJournal of Electromagnetic Analysis and Applications 2012, 4, 15-20 :dx.aoi.org/!0.4236/iemaa.012.41003 Published Online January 2012 ( : SciJRP.org/joumal/jemaa)Analysis of Harmonic Current in Permanent Magnet Synchronous Motor and Its Effect on Motor TorqueXiaoyuan Wang1, Wei Zho
2、u1, Ruzhen Dou2,School of Electrical Engineering & Automation, Tianjin University, Tianjin, China; 2China Automotive Technology & Research Center, Tianjin, China.Email: xywang62Received November 14th, 2011; revised December 12th, 2011; accepted December 22nd, 2011ABSTRACTThe inverter is used as the
3、power supply of modern permanent magnet synchronous motor (PMSM). The inverter may produce harmonics in inversion process and form harmonic currents in motor stator winding which can lead to factors against motor smooth operation such as torque fluctuating and winding heating. This article focuses o
4、n the harmonic currents formed in the motor stator winding by getting the harmonics frequency spectrum with software. The effect of harmonic currents to motor torque is analyzed with the finite element method (FEM).Keywords: Harmonic Current; Inversion; Torque Ripple; SPWM; Finite Element Method1. I
5、ntroductionWith the development of power electronic technology, rapid growth of frequency conversion technology was realized. A new theory of Pulse-Width Modulation (PWM) was advanced in the 1960s by scientists. The modulation technique used in communication field was brought into the application of
6、 AC frequency converters. The Sine Pulse-Width Modulation (SPWM) technique has been applied in inversion since 1970s, making the performance of inverter greatly improved and being widely spread 11.The principle of PWM control is to control the on-off states of power electronic switches in order to o
7、btain a series of pulse waves with same amplitude but different width. The pulse waves are used to replace the required waves, particularly sine waves 2. By modulating the width of pulses according to specific rules, output voltage as well as frequency can be changed. This is the basis of many contr
8、ol strategies 3.Permanent magnet synchronous motor driven by inverter is controlled easily. However, some problems also come out. Only the wave with approximately expected but not the exactly same shape can be obtained with PWM. The harmonics may be generated during the process of sine wave modulati
9、ng using carrier wave, accordingly the performance of PMSM is influenced to some degree. This article mainly studied the effect of harmonic currents produced during SPWM modulating on the torque of motor.2. IntroductionWith the development of power electronic technology, rapid growth of frequency co
10、nversion technology was realized. A new theory of Pulse-Width Modulation (PWM) was advanced in the 1960s by scientists. The modulation technique used in communication field was brought into the application of AC frequency converters. The Sine Pulse-Width Modulation (SPWM) technique has been applied
11、in inversion since 1970s, making the performance of inverter greatly improved and being widely spread 11.The principle of PWM control is to control the on-off states of power electronic switches in order to obtain a series of pulse waves with same amplitude but different width. The pulse waves are u
12、sed to replace the required waves, particularly sine waves 2. By modulating the width of pulses according to specific rules, output voltage as well as frequency can be changed. This is the basis of many control strategies 3.Permanent magnet synchronous motor driven by inverter is controlled easily.
13、However, some problems also come out. Only the wave with approximately expected but not the exactly same shape can be obtained with PWM. The harmonics may be generated during the process of sine wave modulating using carrier wave, accordingly the performance of PMSM is influenced to some degree. Thi
14、s article mainly studied the effect of harmonic currents produced during SPWM modulating on the torque of motor.3. Finite Element Model of the Motor and SPWM External CircuitFinite element method is a good analytic approach which is widely used in electromagnetic field. The finite element model of t
15、he PMSM is built in this study. The motor is a 4-pole motor with rated frequency of 5() Hz, rated voltage 220 V, rated speed 1500 r/min. The connection between the motor and SPWM inverter drive circuit is made through the external circuit software. After voltage was loaded, results can be obtained t
16、hrough the Fourier transform of the data. The amplitude, phase angle of motor harmonic current and other related information are available as well. And parameter of selected PMSM is shown in Table 1.The significance of using finite element software cosimulation for harmonic analysis is that FEM meth
17、od has higher accuracy. Traditional software such as MATLAB can be used for harmonic analysis, but the accuracy of the specific parameters of selected motor cannot be guaranteed. Being not able to establish an accurate motor model, the precise data of the harmonic currents as ones in specific finite
18、 element model cannot be obtained which will result in errors.The finite element model of the motor is shown in Figure 1.The mesh plot of the PMSM is shown in Figure 2.SPWM three-phase bridge inverter circuit is shown in Figure 3. 6-pieces IGBTs are used as power switching devices of full controller
19、 bridge.JEMAACopyright 2012 SciRes.16Analysis of Harmonic Current in Permanent Magnet Synchronous Motor and Its Effect on Motor TorqueFigure 1. Finite element model of permanent magnet synchronous motor.The SPWM external circuit is connected. Sine wave is selected as the modulation wave. Triangle wa
20、ve is selected as the carrier wave. There are the crossover points between the modulation wave and carrier wave. The time of those points decides on-offs time of the inverter switches. The pluses with same amplitude and varying widths are produced 4. Next several points should be concerned in the es
21、tablishment of the external circuit.I) There is a phase difference of 120 degrees between two phases in modulation wave interaction. The initial phase angle should be appropriate. The match between theFigure 2. Mesh plots of the PMSM.一 1HaslCQo-Yy- 810 SJ/N301手汽4UFigure 3. SPWM main circuit.Table 1.
22、 Parameter of the selected PMSM.power rating550 wrated voltage220 Vrated frequency50 Hzrated speed1500 rpmrotor poles4number of stator slots24stator outer diameter120 mmrotor outer diameter74 mmiron core thickness65 1T1IT1fundamental wave phase angle and the motor ones can be ensured during invertin
23、g.2) The ratio of the carrier wave frequency to the modulation wave frequency should be odd and integer times of 3. The even harmonics can be eliminated. The positive and the negative half-cycle waveform are symmetrical. The three-phase output waveform are strictly symmetrical too.3) The fundamental
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