Aiming at extending the output speed range of fourphase switched reluctance motors, a new asymmetric Ttype power converter is proposed. The power converter is composed of modified Ttype threelevel converters and auxiliary circuits. Ttype converter is a multilevel converter which can provide more flexible phase control. The DClink capacitors in the auxiliary circuits are used for voltage level clamping as well as DC voltageboosting 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 neutralpoint clamped (NPC) multilevel converters on efficiency and cost. The simulation results show that the proposed new Ttype power converter increases both speed and output power, improves the efficiency of SRM system, and is suitable for high speed applications.