88 Iranian Journal of Electrical & Electronic Engineering, Vol. 9, No. 2, June 2013

Electromagnetic Analysis of Hysteresis Synchronous Motor Based on Complex Permeability Concept S. M. Mirimani*, A. Vahedi*, M. R. Ghazanchaei* and A. Baktash*

Abstract: Hysteresis motor is self-starting synchronous motor that uses the hysteresis characteristics of magnetic materials to make torque. There are different methods to model this kind of motor and take into account the magnetic hysteresis characteristic of the rotor hysteresis ring. In this investigation the application of complex permeability concept is implemented to model the hysteresis loop and the hysteresis loop in inclined ellipse shape is adopted. To the best knowledge of the authors, this has not been studied before. Based on this concept, simulation of hysteresis motor in conventional configuration is done in order to obtain the output values of motor using 3D Finite Element Model (FEM). This 3D finite element model has high level accuracy and gives better insight of motor performance. Meanwhile, in order to validate the simulation results an experimental set-up is provided and the output values of typical motor are measured. It is shown that there is a good agreement between experimental and simulation results. Keywords: 3-D Finite Element Method, Complex Permeability, Hysteresis Motor.

1 Introduction1 Hysteresis motors have some good characteristics such as soft torque, simple construction with conventional three phase stator windings and self-starting torque. These advantages make the hysteresis motor suitable for some applications such as compressors, pumps, timing, and recording equipment. Although, hysteresis motor in contrast to Permanent Magnet Synchronous Motor (PMSM) has lower output power per unit volume, lower power factor and efficiency and higher magnetizing current [1], But limitation such as zero starting torque, needs to auxiliary winding for line starting and closed loop control systems have confined the usage of PMSM for special applications. Hysteresis motor overcomes these limitations by using the hysteresis characteristics of the magnetic materials. It should be noted that the magnetic characteristics of the motor could be easily affected by hysteresis material, structural dimensions and winding distributions [2]. To have a good designing for these parameters of machine, it would be desirable to adopt an accurate model for the motor. Analytical methods have been used to study the hysteresis motors frequently. However, these methods are very complex when accurate evaluation of the saturation effects, and Iranian Journal of Electrical & Electronic Engineering, 2013. Paper first received 9 Jan. 2012 and in revised form 13 Jan. 2013. * The Authors are with the Center of Excellence for Power Systems Automation and Operation, Iran University of Science & Technology (IUST), Tehran, Iran. E-mails: Mehdimirimani@iust.ac.ir, avahedi@iust.ac.ir, mrghazanchaei@elec.iust.ac.ir and Amir_baktash@ee.iust.ac.ir.

stator and rotor slotting is needed. These problems are overcome by applying numerical methods. Finite element method allows a precise analysis of magnetic devices taking into account geometric details and magnetic nonlinearity. In previous studies, 2D finite element (FEM) techniques for simulating of hysteresis motors have been developed [2-4].

In this paper, the performance characteristics of hysteresis motor through a 3D finite element analysis (FEA) are provided. 3D model has high level of accuracy and gives us a better insight of motor characteristics. Such simulation is based upon Maxwell’s field equations considering the case of a circumferential flux type machine at synchronous speed. There are mainly three methods to take into account the magnetic hysteresis of the rotor hysteresis ring. One is based on the approximation of a parallelogram [5] and the second one is the Preisach model [2, 6, 7] and the last one is based on elliptical model [8]. In this study, the application of complex permeability concept is implemented in order to model the hysteresis loop in the shape of inclined ellipse. To the best knowledge of the authors, this has not been studied before.

Finally, in order to validate the simulation an experimental set-up is provided and output characteristics of conventional hysteresis motor are measured. There exists a reasonably close agreement between the FEM results and experimental set-up output characteristics. Furthermore, this study can be used in the design approach and precise analysis of hysteresis motors.

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Mirimani et al: Electromagnetic Analysis of Hysteresis Synchronous Motor Based on … 89

2 Structure and Winding Configuration Hysteresis motor is a kind of special motor with

outstanding structural features. This type of motor has not slot on its rotor and the rotor structure is quite simple. The structure of a typical two pole hysteresis motor is shown in Fig. 1. The inside surface of the stator has teeth and slots and the conventional three phase windings is implemented in stator. Rotor is generally designed as a cylindrical type motor and made up of two parts. Firstly, hysteresis ring which is the basic element for the torque providing that is made of semi hard magnetic material and can conduct flux circumferentially. Secondly, the hysteresis ring holder; which almost is made of the nonmagnetic material such as aluminum and its alloys. This part of rotor has not any effect on the torque providing and only is the copulative between the rotor and the motor shaft. 3 FEM Model

Since the presentation of the theory of hysteresis torque by Steinmetz in 1908, many authors analyzed the hysteresis machine based on the approximation of representing the hysteresis loop. The hysteresis loop was replaced by inclined ellipse by Teare, Roberts, Miyairi and Robertson in their analysis of the hysteresis motor.

Fig. 1 different parts of hysteresis motor (1) Holder, (2) Hysteresis ring, (3) Stator and winding

In this study, a complex permeability is used to predict the hysteresis loop in hysteresis motor for first time. The aim of the following discussion is to investigate the validity of such application. A useful tool for dealing with magnetic effects is the complex permeability. While at low frequencies in a linear material the magnetic field and the auxiliary magnetic field are simply proportional to each other through some scalar permeability, at high frequencies these quantities will react to each other with some lag time [9]. These fields can be written as phasors, such that:

ω , ω δ (1)

where δ is the phase delay of B from H. Understanding permeability as the ratio of the magnetic field to the auxiliary magnetic field, the ratio of the phasors can be written and simplified as:

μω δ

ωδ (2)

So that the permeability becomes a complex

number. By Euler's formula, the complex permeability can be translated from polar to rectangular form:

μ cos δ δ μ μ (3)

The ratio of the imaginary to the real part of the

complex permeability is called the loss tangent:

δ (4)

which provides a measure of how much power is lost in a material versus how much is stored.

Fig. 2 helps us to exploit desired parameter as a function of Hmax, HC and Bmax [9, 10].

µµµ µ

(5)

δ (6)

µ ′ µ cos δ (7)

µ ′′ µ sin δ (8)

where δ is hysteresis lag angle between flux density and magnetic field intensity, rμ is the relative permeability,

'rμ and ''

rμ are the real and imaginary parts of complex permeability.

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References [1] Rahma

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es diagram of f

lation results foQuantity

y state torque (N

y state current (

P input(Watt) Power Factor fficiency (%)

in Fig. 7, hyctly like a permibutions the o

d shown in Tabfrom Tables

between outpud one.

ion aper, a novel

d for accuratsteady state

ated. A hysterepted to approxn method is p. The simulaor is done. f the model d output quanIt was showbetween sim

an M. A. aronization of

I

flux density of r

or Hysteresis mv

Nm) 0

(A)

ysteresis ringmanent magnoutput quantitble 3. s 2 and 3, tut quantities

finite elemente analysis o

characteristicesis loop in anximate the rea

implementedation based on

In order to an experim

ntities of protwn that theremulation resu

and Qin R.Permanent M

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otor values

0.0112

0.435

66.7 0.59 42

g at synchronnet. Based on fties of motor

there is a clof actual mo

nt analysis moof the hystercs of the mon inclined elli

al hysteresis lod to model n dimensions o

investigate mental set-uptotype motor e is reasonaults and mo

, "Starting Magnet Hyster

nal of Electrica

nous flux are

lose otor

odel esis otor ipse oop.

the of a the

p is are

ably otor

and esis

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Analytical Solmotor Based Transaction

o. 1, pp. 156-1rder Accurate

me-Harmonic degree of Division

University, M

Mehdi Mirimanan. He receivfrom the Uan, Babol, in ree on the subje

from Iran nd Technologywhere he is cure Ph.D. degreof Electrical En

2, June 2013

on Industry3-1189, 1996.S. K., “Finitetor Using the

Model”, IEEE4, No. 5, pp.

and Jung H.teresis Motorodel”, IEEE6, No. 4, pp.

K., “Analysisnite Elementdent Model”,ol. 36, No. 4,

for Polyphaseons on Power92, No. 1, pp.

ackson R. D.,, “Improvedof hysteresisterials”, IEEE17, Nov. pp.

on J., “Vectored Magneticn Magnetics,1994. Analysis of aSpeed UsingTransaction

. 9, No. 2, pp.

etism, Berlin:

lution for theon Complexon Energy

63, 1990. e Methods for

Maxwell’sf Doctor of

of AppliedMay 2006.

ni was born inved the B.Sc.University of

2007 and theect of electricalUniversity of, Tehran, Iran,

rrently workinge in electricalngineering. His

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Mirimani et a

research interefinite-element electromagnet

Optimization, He is currenEngineering ais also membautomation &

al: Electroma

ests include thanalysis of

tic devices.

Abolfaz1989 froand MrespectiPolytechFrance) has direof Elecresearch

Monitoring anntly Professor

at Iran Universiber of Center o

Operation.

agnetic Analys

he design, modelectrical ma

zl Vahedi receom Ferdowsi M

M.Sc & Ph.D ively from Ihnique de all in Electrica

ected several pctrical Machineh interests arend Control of Er in Departmity of Science &of Excellence

sis of Hysteres

eling, control, achines and o

eived his B.ScMashhad Univerin 1992 and 1Institute Natio

Lorraine (INal Engineering.

projects in the es & Drives. e mainly DesElectric Machi

ment of Electr& Technology.for Power Sys

sis Synchrono

and other

c in rsity 1996 onal

NPL-. He area His

sign, ines. rical . He stem

appma

pul

us Motor Bas

plication of FEachines.

lsed power tech

ed on …

Mohammaborn in 1received hiof Iran TechnologyElectrical Efinishing hUniversity (IUST), Teinterests in

EM to design

Amir Baktin ElectUniversity Electrical University (IUST) in Now he is research indrives, Ele

hnology.

adreza Ghaz1986 in Tehris B.S. degree frUniversity ofy (IUST), IranEngineering. Phis Msc. pro

of Science &ehran, Iran. Hisnclude dynamic

and modeling

tash received htronic Engin

of Yazd anEngineering

of Science &2004 and 2007a PhD studen

nterests include ectrical motor

93

zanchaei wasran, Iran. Hefrom Universityf Science &n, in 2007 in

Presently, he isogram in Iran& Technologys main researchc modeling andg of electrical

his BS degreesneering fromd his MS in

from Iran& Technology7, respectively.t in IUST. Hisvariable speed

s design, and

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