针对将电磁轭直接用于市电220 V或直接接于逆变器中时出现的过电压现象，分析了产生过电压的原因，说明了过电压的危害性，并指出当频繁断开励磁电流时，出现过电压的可能性会急剧增大。提出了消除电磁轭过电压的两种方法，结果表明，采取抑制过电压后的电磁轭，使用220 V的交流电压进行磁粉检测是可行的。

With the improvement of electromagnetic yoke insulation performance and voltage resistance level, it is possible to directly connect the yoke with the lines of 220 V or directly connect it to the inverter power supply transformer for the purpose of reducing the weight of the portable magnetic particle testing instrument. By doing so, on the other hand, the potential hazard to safety may arise and in some cases overvoltage may occur, which threatens the safety of equipment and personnel. This paper analyzes the causes of overvoltage, illustrates its harmfulness, and especially points out that the possibility of overvoltage occurs when the excitation current is frequently cut off. Two methods for eliminating overvoltage are proposed. It is advisable to use an alternating current of 220 V to carry out magnetic particle testing if the above-mentioned measures are taken in advance.