誘導溶解炉におけるサイリスタ故障のトラブル分析

誘導溶解炉でのサイリスタの故障には、回路やサイリスタ自体の品質など、多くの理由があります。 サイリスタ故障の主な故障を以下に分析します。

（L）誘導溶解炉のサイリスタの抵抗容量吸収回路の巻線抵抗が飛んだり、断線したりして、サイリスタが故障したり、特性が劣化したりします。 回路にラインインダクタンス（変圧器の漏れインダクタンスLB、リアクトル）が存在するため、サイリスタはターンオフプロセス中にターンオフ過電圧を引き起こし、その値はピーク動作電圧の5〜6倍に達する可能性があります。サイリスタが故障しやすい、または特性が悪化します。

(2) Induction melting furnace inverter bridge conversion contactor due to contact sintering, mechanical failure, or the setting value of the conversion potentiometer is too large, after the inverter is switched, the contactor cannot be opened or switched, resulting in a current-limiting magnetic ring Does not work, causing thyristor breakdown. In the commutation process of the thyristor, due to the commutation current, capacitor discharge, etc., it will cause a larger current rise rate du/df, and a larger current rise rate will make the internal current of the thyristor too late to spread to all PN junctions. As a result, the PN junction near the gate of the thyristor is burned due to excessive current density, causing the thyristor to break down. The magnetic ring set on the inverter bridge can effectively limit the current rise rate d//df and protect the thyristor.

(3) After the overcurrent protection action of the induction melting furnace occurs, the rectification trigger pulse disappears, causing the rectifier thyristor to turn off, causing the thyristor to breakdown.

We know that when an over-current protection action occurs, the rectifier trigger pulse is shifted to 150 degrees, so that the rectifier bridge is in an active inverter state, and the energy stored in the filter reactor is sent back to the grid to prevent the thyristor from being over-current. , The impact of overpressure. When an over-current action occurs, the rectifier trigger pulse disappears. When the rectifier thyristor is turned off, a high turn-off over-voltage will be generated, so that the thyristor will withstand the impact of over-current and over-voltage, which can easily cause the breakdown of the thyristor. This kind of failure is generally caused by the deterioration of the characteristics of the output low-power thyristor on the blocking protection board or the increase of the power supply. It can be solved by connecting a 4.7k potentiometer in series in the circuit, and the actual resistance value is determined by debugging on the computer.

（4）誘導溶解炉のサイリスタの冷却水管が詰まり、湿度が高すぎてサイリスタが故障します。

（5）サイリスタ自体の品質が悪い、または過電流や過電圧の影響を何度も受けているため、サイリスタの特性が劣化したり故障したりします。