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This article proposes a novel asymmetric interior permanent magnet (AIPM) rotor topology that has a mixed V-shape and spoke-type PM configuration, designated as a 1.5-layer PM structure, and asymmetric arrangement of V-shape PMs and asymmetric flux barriers. The AIPM rotor topology is employed for IPM synchronous machines to utilize the magnetic-field-shifting (MFS) effect for increasing average torque by reducing the current angle difference between peak PM and reluctance torque components. Three machines, i.e., the proposed 1.5-layer AIPM, a symmetrical 1.5-layer IPM-I, and a conventional V-shape benchmark IPM-II are designed and optimized using the same stator, rotor diameter, and total PM usage by global parametric optimization considering the mechanical stress. The effect of asymmetric features of the 1.5-layer AIPM rotor design, i.e., asymmetry of V-shape cavity as well as position and dimensions of flux barrier, on maximum torque and open-circuit air-gap field are investigated. The electromagnetic performances of three machines are compared. It confirms that the proposed AIPM machine has the highest maximum torque and the smallest cogging torque simultaneously. It is also revealed that the torque enhancement is achieved by both the 1.5-layer structure and MFS effect. Finally, a prototype of an AIPM machine is manufactured and tested to validate the analyses. [ABSTRACT FROM AUTHOR]