# Modeling of Electric Machines for Mautomotive Application

Topics: Electric motor, Electric vehicle, Hybrid electric vehicle Pages: 16 (3752 words) Published: May 4, 2013
MODELING OF ELECTRIC MACHINES FOR AUTOMOTIVE APPLICATIONS USING EFFICIENCY MAPS S. M. Lukic and A. Emado Illinois Institute of Technology
Abstract: In most industrial applications of motor drives, motors operate at one or a few predefued operating points. However in propulsion applications, the motor is used over the entire torqudspeed range. Therefore, the motor has to be studied at all possible torqudspeed combinations within the motor operating envelope. Efficiency maps are a convenient way to represent motor drive subsystem of a large, complex, system like a vehicle. Efficiency maps give the system engineer an idea about the torqudspeed combinations at which a specific electrical motor drive is eflicient, thus allowing for a more efficient design. In this report we look over the efficiency characteristics of motors that are most commonly used for propulsion applications. We also quantify typical load on motor drives in vehicles that use electric propulsion - namely Electric Vehicles (EV) and Hyhrid Electric Vehicles (HEV). I. INTRODUCTION

In most industrial applications of motor drives, motors operate at one or a few predefined operating points. Therefore the motor can be optimized to give the best performance at these specific points, and the efficiency of the system is well defined. However in propulsion applications, the motor is used over the entire torqudspeed range. The motor must be designed for frequent stadstop, and high acceleration and deceleration rates (meaning high torque output for the entire speed range) [I]. Hence. the motor needs high torque density and efficiency at all speeds [2]. Also, the motor drive needs high controllability, steady state accuracy, and good transient performance [3-51. Therefore the performance characteristic of a propulsion motor must be quite different from the industrial motor drive. The motor has to be studied at all possible torqudspeed combinations within the motor’s operating envelope.

Losses
(Friction, Copper...)
Figure I . Block Diagram of motor modeling using efficiency maps In this report we look over the efficiency characteristics of motors that are most commonly used for propulsion applications. We explain why we see different optimal efficiencies for different machines, by accounting for losses in different operating regions. We also quantify typical load on motor drives in vehicles that use electric propulsion - namely Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV). 11. PROPULSION DRIVES AND THEIR EFFICIENCY MAPS

C.C. Chao noted that “research papers on induction motor (IM) drives and permanent magnet (PM) motor drives are highly dominant, whereas those on direct current (DC)motor drives are dropping while those on switched reluctance (SR) motor drives are still in a crawling stage”l61. Also, [7-91 show that ac drives have some inherited advantages for propulsion applications over dc drives. In order to be able to determine the efficiency of a motor drive, it is essential to understand how each loss component changes with motor speed, and eventually vehicle speed. While it is not possible to obtain a generalized map for specific machine type, we discuss the losses (core, copper, or mechanical) that are prevalent in certain regions of the torqudspeed curve and offer efficiency maps that show this general trend.

Efficiency maps are a convenient way to represent motor drive subsystem of a large, complex, system like a vehicle [ I , 21. By using efficiency maps, motor is represented as a “black box” that provides a known output when certain input is applied (Figure I). The assumption is that the inputs are optimized so as to get the highest efficiency at a specific torque and speed output.

0-94 I783-23-5/03/\$17.0002003 IEEE

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A. Permanent Magnet SynchronousMotor (PMSM)

PMSM are the...

References: Volume: 37 Issue: 5 , Sept.-Oct. 2001 Page(s): 1256 -1264
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6. C.C. Chan, ‘“The state of the art of electric and hybrid vehicles” Proceedings o fhe IEEE, Volume: 90 f Issue: 2 . Feb. 2002 Page(s): 247 -275
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