滑差频率对磁浮车辆运行性能的影响

采用二维电磁场理论对直线电机气隙磁场的纵向分量和垂向分量进行求解, 得到了电机牵引力和法向力的解析表达式, 利用直线电机试验台对解析计算方法进行检验, 对比6~18 Hz恒滑差频率下牵引力和法向力随速度的变化; 建立了三悬浮架单节磁浮车辆动力学模型, 仿真对比了车体和悬浮架分别在1、3、5、8 kN冲击力下的振动响应; 计算了单节中低速磁浮车辆牵引特性, 分析了不同滑差频率对车辆牵引性能的影响; 综合考虑电机法向力对悬浮系统的影响和车辆的牵引需求, 提出了变滑差频率控制策略。研究结果表明: 电机牵引特性一般包括恒力区和恒功区, 恒力区初级电流最大值为390 A, 恒功区电压最大值为212 V, 恒力区牵引力变化较小, 恒功区牵引力衰减较快; 滑差频率越小, 电机起动牵引力和法向力越大, 恒力区越短, 反之亦然; 法向冲击力小于8 kN时车辆平稳性指标等级均达到优秀, 但为了减小悬浮系统的负担, 电机法向力应越小越好; 较低的滑差频率使车辆低速段牵引性能更强, 但采用较高的滑差频率有利于提高全速度范围的牵引性能; 在变滑差频率控制策略中起动滑差频率的选择综合考虑车辆的牵引性能和悬浮能力, 速度达到恒功转折点后滑差频率逐渐增大, 该策略使电机恒力区牵引力适中, 恒功区牵引力始终为电机所能发挥的最大值。 

Influence of slip frequency on running performance of maglev vehicle

The longitudinal and vertical components of air gap magnetic field of linear induction motor(LIM) were solved by the two-dimensional electromagnetic field theory, and the analytical expressions of traction force and normal force of LIM were obtained. The analytical calculation method was tested by using the test bench for LIM, and the variations of traction force and normal force with speed under the constant slip frequency range of 6-18 Hz were compared. The dynamics model of a single maglev vehicle with three levitation frames was built. The vibration responses of car body and levitation frame under the impact forces of 1, 3, 5 and 8 kN were simulated and compared. The traction performance of a single middle-low speed maglev vehicle was calculated, the influence of slip frequency on the traction performance of vehicle was analyzed. Considering the influence of normal force on the levitation system and the traction demand of vehicle comprehensively, the variable slip frequency control(VSFC) strategy was proposed. Research result shows that the traction characteristic of LIM generally contains the constant force zone(CFZ) and constant power zone(CPZ). The primary current in the CFZ reaches a maximum of 390 A, and the voltage in the CPZ reaches a maximum of 212 V. The traction force in the CFZ changes little, and decreases rapidly in the CPZ. The smaller the slip frequency is, the greater the starting traction force and normal force of the motor are, and the shorter the CFZ is. When the normal impact force is less than 8 kN, the vehicle stability index grades are all excellent. However, in order to reduce the load of levitation system, the normal force of LIM should be as small as possible. The traction performance of vehicle in the low speed zone under lower slip frequency is better than that under higher slip frequency, but the higher slip frequency is beneficial to improve the traction performance in the full speed range. In the VSFC strategy, the selection of starting slip frequency takes into account the traction performance and levitation ability of vehicle, and the slip frequency gradually increases after the speed reaches the turning point of constant power. Under the VSFC strategy, the traction force is moderate in the CFZ, and is always the maximum value that the motor can exert in the CPZ.