What is the reason for the unsuccessful start of the intermediate frequency melting furnace ?

I have a one-ton intermediate frequency melting furnace , and the control panel can be activated (impact board), but it will often sweep up and down before starting, and the frequency will not start. Is the frequency of the board adjusted for the size of the angle? Or other reasons? Please do not hesitate to teach in the industry , this situation is generally more likely to occur under full load. The reason may be that the startup speed is too fast, the angle is not adjusted, and the load capacitance is not matched (such as the capacitance capacity due to the use time). Longer and smaller) There is also the start signal is disturbed (can be shielded)

It is very likely that the feedback amplitude is insufficient. Synchronization is difficult or the pulse advance angle is not suitable for board regulation and load matching.