Research on a unistor equivalent circuit of linear induction motor and its parameter estimation.

通过对基于虚单元单极的直线感应电机三相等值电路的分析，明确了以下几点：(1)三相直线感应电机在驱动状态下各端输入电压和电流不平衡。产生这种现象的原因在于直线电机的端部效应，因此直线电机应该用一个四端的三相等效电路来表示，而不是用一个单相等效电路来表示。(2)由于直线电机的影响，气隙中的磁场分布随二次导体的速度而变化。等效电路上的铁耗等参数是速度的函数。因此，电路参数的确定应在驱动条件下进行。(3)利用复功率矩阵估计功率分布。根据功率矩阵，在直线电机和电源的各相功率通常是不平衡的。(4)估算了各相二次功率对二次电阻的瞬时影响。这种瞬时二次动力会产生推力波纹。由于推力波纹与垂直输送机械系统共振是危险的，减小波纹是当前最需要解决的问题。(5)从瞬时二次功率方程出发，推导出推力波纹系数K_C和K_S。通过对立式传动系统中圆柱体直线电机的测量，验证了它们的正确性。

By analyzing a 3-phase equivalent ciercuit of linear induction motor (LIM) based on an imaginary element unistor, investigators made the following points clear.(1) Input voltage and current on each terminal of 3-phase LIM are unbalanced under the driving condition. The cause of this phenomenon comes from the end effect of LIM.Therefore LIM should be represented by a 3-phase equivalent circuit with 4 terminals, not by a single phase equivalent circuit.(2) By reason of the effect of LIM,magnetic distribution in the air gap changes with velocity of secondary conductor. The iron loss and other parameters on the equivalent circuit are the functions of velocity. Therefore the determination of circuit parameters should be done under the driving condition.(3) The distribution of power was estimated by the complex power matrix. According to the power matrix, the power is usually unbalanced in each phase of LIM and source.(4) The instantaneous secondary power on the secondary resistance in each phase was estimated. This instantaneous secondary power produces the thrust ripple. As the thrust ripple is dangerous if it resonate with mechanical system of the vertical transportation, the decrease of ripple is the most problem to solve today.(5) Ripple coefficients K_C and K_S were induced and estimated from the equations of instantaneous secondary power. They were verified by the measurement of cylindrical LIM in vertical driving system.