High-Efficiency Technology for Railway-Vehicle Traction Motors

This paper presents high-efficiency technology for railway-vehicle traction motors, looking at the latest development of induction motors (IMs) and permanent magnet synchronous motors (PMSMs). A proposed high-efficiency IM realized decrease in stray load loss and harmonic losses as well as fundamental loss, where the magnetic wedges inserted into stator slot openings smoothed gap magnetomotive force (MMF) distribution and then let air-gap length be shortened. Measurement tests of a developed IM demonstrated the reduction of iron and stray-load losses by 32% and hence total losses by 63%, resulting in the high efficiency of 96.8%. Another proposed high-efficiency technology for PMSMs is asymmetrical magnetic poles which reduces cogging torque and torque ripple without impairing DC component of output toque under MTPA (maximum torque per ampere) control, and then achieved nominal efficiency of 98%. Commercial operation tests of the proposed PMSM demonstrated the loss reduction of 10 to 15 % compared with a conventional IM drive system.