Aiming at extending the output speed range of fourphase switched reluctance motors, a new asymmetric Ttype power converter is proposed. The power converter is composed of modified Ttype threelevel converters and auxiliary circuits. Ttype converter is a multilevel converter which can provide more flexible phase control. The DClink capacitors in the auxiliary circuits are used for voltage level clamping as well as DC voltageboosting capacitors to produce additional voltage during the rise and fall period of a motor phase current. The operation and analysis are detailed for different operation modes. Comparisons are made between the proposed converter and diode neutralpoint clamped (NPC) multilevel converters on efficiency and cost. The simulation results show that the proposed new Ttype power converter increases both speed and output power, improves the efficiency of SRM system, and is suitable for high speed applications.