脉宽调制激励下材料铁损自动测量系统研制

Development of automatic iron loss measurement system with PWM excitation

随着供电方式的变革,越来越多的电工设备工作在脉宽调制模式(PWM)的激励下,而通常铁心材料生产厂家只提供基于正弦磁密激励的铁损曲线,参考价值有限,另外商用的铁损测量仪均是基于正弦磁密模式。针对此情况,提出了一种铁损自动测试系统的硬、软件实现方案,详细阐述了其测量原理,推导了铁损测量误差的解析表达式,指出信号的相位差是影响测量精度的关键;对比实验表明,引入隔离变压器可以有效地解决测量过程中的直流偏磁问题。最后,研制了PWM工作方式下的铁损自动测试系统,经校准后,测量重复性在3%以内,试运行后的初步结果表明,PWM工作方式下的铁损值较同等基波磁密条件下的铁损值大,母线电压越高,调制比越低,铁损越大。

With the development of power supply technology, more and more electromagnetic devices are supplied by pulse width modulation （PWM） converter. However, steel manufacturers only provide iron loss curve of silicon steel excited by sinusoidal magnetic flux density, which is of limited reference value. In addition, commercial iron loss testers are also based on sinusoidal magnetic flux density. In this situation, we proposed an applicable scheme for hardware and software implementation, and elaborated the measurement principle, deduced the analytical expression for error estimation of measurement result, pointed out that phase difference is the key factor influencing the accuracy. By comparison experiment, it was testified that introduction of isolation transformer can effectively eliminate the DC bias magnetization. At last, an automatic iron loss measurement system with PWM excitation was made. After calibration, its repeatability is within 3%. Preliminary result showed that iron loss value of material under PWM excitation is higher than that under sinusoidal excitation assuming both cases have identical fundamental magnetic induction, and the higher the DC bus voltage, the lower the modulation index, and the higher the iron loss will be.