中频感应加热装置的最佳阻抗匹配

STUDY OF THE BEST IMPEDANCE MATCHING TO MIDDLE FREQUENCY INDUCING MELTING STOVE

中频感应加热装置冷态起动性能差，加热功率低，是目前中频感应加热装置普遍存在的主要问题。为了改善冷态阻抗匹配，提高加热功率，分析了造成初加热功率小的原因及其对中频电源的危害，得出了中频感应加热装置从低温到高温的加热全过程中负载特性的变化规律及负载阻抗与工件电阻和谐振电容之间的关系。采用根据等效负载阻抗模型调整初加热中频电源的谐振电容的方法，改变负载等值阻抗，使负载达到最佳匹配。对于现有的中频装置，可通过切换谐振电容组，在高、低温条件下分别实现负载阻抗与电源的最佳匹配，从而提高初加热时的功率，加快熔炼速度，减小散热损失，实现降低能耗的目的。

At present,the main shortcomings of middle frequency inducing heating equipment arepoor in performance and low in heating power at cold starting. In order to improve theimpedance matching at cold state and raise the heating power,the reasons of low heatingpower at initial heating and the dangers to the power supply source of middle frequency wereanalysed in this paper. The change Jaw of load characteristics of middle frequency inducingheating equipment in all heating process and the relationship between load impedance andresonance capacitance were found out.According to the model of equivalent load impedance,regulating the resonance capacitance of power supply source of middle frequency at initialheating and changing the equivalent impedance of load,the best impedance matching of loadwas achieved.For the current middle-frequency equipment, the best matching between loadimpedance and power supply source can be completed at the low temperature and at the hightemperature respectively by switching over the group of resonance capacitances.Then thepower efficiency at initial heating is raised,the melting speed is accelerated,the heat loss isreduced,and the purpose of decreasing energy loss is reached.