Abstract：A brake unit based on IGCT was designed for different applications of frequency converter in

industrial scenes，especially the medium voltage frequency conversion system without feedback function. IGCT

was used as the main power device，and the parameters and characteristics of IGCT was analyzed. According to the

common topology of NPC medium voltage inverter in the market，the matching circuit of brake unit was designed，and the working principle of the system was described. In terms of device loss，the junction temperature of the power device was evaluated，and the water cooling circuit and the press assembly structure were designed. In order not to affect the midpoint balance of the DC bus voltage，an independent software control method was designed.Finally，the medium voltage brake unit designed has been applied to the occasion of rolling metal composite material in the indμstrial field，which confirmed the feasibility of the design scheme.

      Key words：integrated gate-commutated thyristor（IGCT）；brake unit；absorbing circuit；three-level NPC

inverter；thermal loss