发电电动机SFC起动强迫换流过程磁场特性

Magnetic field harmonics of generator / motor starting with SFC during forced commutation operation

针对发电电动机静止变频器(static frequency converter,SFC)起动强迫换流过程运行特点,分别推导出了发电电动机在由电网供电和强迫换流运行过程中的电磁转矩表达式,分析了强迫换流运行导通周期内磁场特征及电磁转矩特性。同时研究了强迫换流导通周期内,定转子磁动势不同匹配系数时合成磁场的分布规律,定量计算了定转子磁场不同相对位置时气隙磁场畸变率及三次谐波占基波的比例随定子磁动势的变化规律,并对不同相对位置对应的气隙磁场畸变率进行了对比分析,提出了通过合理匹配定转子磁动势,降低发电电动机在强迫换流运行过程中气隙磁场畸变率及对应谐波转矩。结果表明,适当提高转子磁动势相对定子磁动势的比例,可以使发电电动机在强迫换流导通周期内保持较低恒定的气隙磁场畸变率。

With the operation characteristics of generator/motor during forced commutation process, elec- tromagnetic torque expressions were deduced while the generator/motor fed with power grid and static fre- quency converter（SFC） , and characteristics of magnetic motive force （MMF） and electromagnetic torque during converter period of the forced commutation process were analyzed. Besides, the magnetic field dis- tribution with different stator and rotor MMF matching factor k~ was studied, and the air-gap magnetic field distortion factor and the ratio of the third harmonic to fundamental wave were calculated quantitative- ly, accounting for the different relative locations of the axes of stator and rotor MMF. Meanwhile, change law of air-gap magnetic field distortion factor and the ratio of the third harmonic to fundamental wave were presented and analyzed contrastively. Based on the analysis and calculation, the approach was proposed to reduce the air-gap magnetic field distortion and harmonic torque by reasonably matching the MMF of stator and rotor. Results indicate that the air-gap magnetic field distortion is kept constant and low during converter period of the forced commutation process through increasing the proportion of rotor MMF appro- priately.