My name is Altaf Jangda

We have Vicor CNC Lathe model VT plus 20. Initially, there was alarm No.6 from spindle drive. After investigation, observed on of the IGBT Power transistor (FUJI ELECTRIC 2MBI200TC-060-01, 200A 600V) burst and some couplers were also burnt in Fanuc Power Supply module drive (A06B-6110-H026).
After replacing IGBT Power trasistor and couplers on Fanuc Power supply module, the machine worked for 3 days and gain 2 IGBT Power transistors burst and couplers again burns in Power supply module when machine statts. Please advice how to find the main cause of burst. Thanks