JT-90井式气体渗碳炉下区是采用φ4.5mm电阻丝制做的电热元件,采用380V、双星形接法,如图1所示。在工作中由于底部电阻丝在氧化铁屑和密封用砂等落入物的掩埋下,很容易被熔化而断路,造成了下区三相电流不平衡,如图2。电阻丝在图2三相不平衡状况下运行,中性点产生位移,使C相所承担的功率 JT-90 pit gas carburizing furnace under the area is made of φ4.5mm resistance wire heating element, using 380V, double star connection, as shown in Figure 1. In the work, since the bottom resistance wire is buried under the objects such as the iron oxide dust and the sealing sand, it is easily melted and disconnected, resulting in the unbalance of the three-phase current in the lower area, as shown in FIG. 2. Resistance wire in Figure 2 three-phase unbalanced operation, the neutral point of displacement, so that the C-phase power