压接型IGBT器件内部芯片电流测量时罗氏线圈的误差分析及改进方法

Error Analysis and Improvement Method of Rogoswski Coil in Current Measurement of internal Chips in Press-pack IGBT Devices

压接型IGBT芯片的并联使用是提高IGBT器件电流等级的重要手段。然而芯片之间的电流不平衡限制了器件的最大额定电流。通常需要通过实验测试的方法评估这种不均流度,然而难点之一是如何准确测量压接型IGBT器件内部芯片的电流。罗氏线圈因其具有灵活、无饱和、非嵌入式等优点,是目前用于压接型IGBT器件内部电流测量的主要手段。已有的研究表明,罗氏线圈在测量压接型IGBT器件内部芯片电流时出现了较大的误差。文中针对罗氏线圈在压接型IGBT器件内部芯片电流测量的特殊应用工况,分析电流测量误差产生的原因;建立罗氏线圈误差模型,并推导误差解析公式;采用误差解析公式提出2种减小测量误差的方法;最后,通过实验验证所提误差解析公式及减小测量误差方法的有效性。

The parallel use of Press-pack Insulated Gate Bipolar Transistor(IGBT) chip is an important means to improve the current level of IGBT devices. However, the current imbalance between the chips limits the maximum rated current of the device. It is usually necessary to evaluate degree of current imbalance by means of experimental testing, but one of the difficulties is how to accurately measure the current in the internal chip of Press-pack IGBT device. Rogoswski coil is the main means of current measurement in IGBT devices because of its advantages of flexibility, non-saturation and non-embedment. Previous studies have shown that there is a large error in measuring the chip current by the Rogoswski coil in the IGBT device. This paper is based on the special application of Rogoswski coil to measure the chip current in Press-pack IGBT devices. Firstly, the causes of current measurement error were analyzed. Secondly, the error model of Rogoswski coil was established and the error analytical formula was derived. Then, two methods to reduce measurement error were proposed. Finally, the effectiveness of the analytical formula of error and the method of reducing measurement error were verified by experiments.