Wound Rotor Synchronous Motor as Promising Solution for Traction
Applications
Asif Hussain 1, Thomas A. Lipo 2, Life Fellow, IEEE and Byung-il Kwon 1,
Senior Member, IEEE
1
Department of Electronic Systems Engineering, Hanyang University, Ansan
426-791, Korea
E-mail: bikwon@hanyang.ac.kr
2
Department of Electrical and Computer Engineering, Florida State
University, Tallahassee FL 32306, USA
This paper presents the wound rotor synchronous motor (WRSM) as
promising alternative of permanent magnet (PM) motor in traction
applications such as electric vehicles (EVs). From last few decades, PM
motors have been the choice for EVs because of their high torque density and
efficiency at rated speed and torque. However, PM motors face serious
problems of lower efficiency under low load conditions because most of the
operating cycle of electric and hybrid vehicles consists of low load operation
and the field weakening region, where WRSM outwits the PM motors (T.A.
Burress, S.L. Campbell, “Evaluation of the 2010 Toyota Prius Hybrid Synergy
Drive System” ORNL/TM-2010/253, Oak Ridge National Laboratory, March
2011). WRSM overcomes this problem because of their ability to adjust the
excitation current. This will not only help to adjust power factor and torque of
the motor, but it will also allow the efficiency optimization below and above
the rated values of the load. Moreover, due to the limited supply of PM
materials and their increasing cost, an alternate solution becomes inevitable.
The aim of this paper is to design the WRSM with competitive performance to
2010 Toyota Prius IPM motor. The power rating and dimensions of the
designed WRSM are kept same as 2010 Toyota Prius IPM motor. The design
of proposed WRSM is based on the constraint that the full load field mmf per
pole is kept same as the armature mmf per pole. Due to this the electrical and
magnetic loading of the proposed motor are not same as the loading of Toyota
Prius IPM motor. However, the product of the both loading is same as Toyota
Prius IPM motor. Two-dimensional (2-D) finite element analysis (FEA) is
performed to analyze the performance of WRSM in constant torque region.
207 Nm torque is achieved at base speed of 2768 rpm. Fig. 1(a) shows the no
load back emf and 1(b) shows the torque of WRSM in constant torque region
at rated conditions. The detailed 2D-FEA analysis of the WRSM in constant
torque region at rated load and in the field weakening region will be presented
in the full paper.
(a)
(b)
Fig. 1: (a) Back emf of WRSM (b) Torque of WRSM