The Study of Demagnetization of the Magnetic Orientation ... · demagnetization of field weakening...

Journal of Electrical Engineering 6 (2018) 144-150 doi: 10.17265/2328-2223/2018.03.002

The Study of Demagnetization of the Magnetic Orientation of Permanent Magnets for IPMSM with

Field-Weakening Control under Hot Temperature

Noriyoshi Nishiyama1, Hiroki Uemura2 and Yukio Honda2 1. Panasonic Corporation, Moriguchi City, Osaka 570-8501, Japan

2. Osaka Institute of Technology, Osaka City, Osaka 530-0013, Japan

Abstract: In this study, we investigate the demagnetization resistance of a concentrated winding IPMSM (interior permanent magnet synchronous motor) accounting for field weakening control by changing the magnetization direction of the permanent magnet under a high-temperature environment. IPMSMs are investigated by FEA (finite element analysis) using the same volume of the permanent magnet while changing the magnet’s width, thickness and magnetic field orientation angle. FEA found that a V-shaped angle Va = 100° and a changed magnet length of 97% using an oblique magnetic-field-oriented magnet strike a good balance between demagnetization resistance and torque at 180 °C. Comparison between demagnetization of negative d-axis current (current phase β = 90°) and demagnetization of field weakening control (β = 80°) using concentrated winding IPMSM with V-shaped angle Va = 100° is conducted. With the demagnetization factor at β = 80° for β = 90°, the demagnetization factor 0.39 (2.6 times) at α = 0° decreases to 0.23 (4.3 times) at α = 20°. The demagnetization resistance in the field weakening control is further improved. Key words: IPMSM, demagnetization, concentrated winding, high temperature, field weakening. 1. Introduction

The high efficiency of a small-sized permanent magnet synchronous motor is one of its key features. On the other hand, one of its disadvantages is that the coercive force decreases at high temperature and then easily demagnetizes. In recent years, motors for vehicles, high-temperature heat pumps, and extreme-environment-compatible robots have had to operate in severe load environments, which are often extremely high-temperature environments where permanent magnets are demagnetized. In this work, we examined a parallelogram-shaped permanent magnet whose magnetic field orientation was made oblique with respect to the plate thickness direction (see Fig. 1). Lm is the magnet length, Am is the magnet cross-sectional area.

Corresponding author: Noriyoshi Nishiyama, doctor of

philosophy in Engineering, research fields: permanent magnet synchronous motor design.

For obliquely distributed magnets with an oblique orientation angle α, the magnetic field orientation inclines from the plate thickness direction with respect to the magnet width Wm and the magnet thickness tm. Furthermore, the operating point of the magnet does not change much from the permeance equation, since the magnetic field H is acting on the magnet. On the other hand, the reverse magnetic field component affecting the magnetization direction of the magnet can be reduced to Hm, thus improving the demagnetization resistance [1, 2].

Few studies have attempted to examine the magnetic field orientation of permanent magnets detailed demagnetization characteristics under high temperature environments [3-8]. A field weakening control that energizes the negative d-axis current component can suppress the induced voltage of the motor and can operate in the wide rotational speed range under a limited power supply voltage [9]. The demagnetization in field-weakening control is likely to

D DAVID PUBLISHING

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urrent causinrotor’s magn

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dymium sinte6 UH) is usedre shown in in Fig. 2. Thlimit current Dr n is defin

ovement rati

(1 - B2/B1) Dr n / Dr 0 fined as Eq. (

T n / T0 s magnetic ld is applied.

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sidual magneticx density Br ercivity Hcj

ectromagnetic el sheet mperature

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145

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146

parallel-oriearrangementparallel-oriearrangement

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3. MagneResistance

Here, we analytical mangle Va is c

Based on flat plate motimes for thspoke modeangle Va isratio Dr n relationship

In the anamagnet lengdemagnetizatorque ratio

For the ratio, the dethe flat-plparallel-orieline; 1). Tparallel-orierotor’s torqucondition oflength of lincreased. O100% or mooblique mag

Although

The Study

ented magnet (Va = 180

ented magnet (Va = 180°)agnetization l

which reductinetic flux of the reverseh 1%. ue is calculacurrent phase

et Lengthe

consider demmodel in whchanged froma 1% demag

odel (Va = 18he Va = 100el (Va = 60°)s changed, dand torque r(see Fig. 3).

alysis results,gth ratio andation resistan(see Figs. 4 ademagnetizatmagnetizatiolate magne

ented magnet The torque ented magneue (circle wif a constant less than 10

On the other ore, the magngnetic-field-or

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et (α = 0°) 0°). T0 is thet (α = 0°) . limit current on of the nodensity, be

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ated with ratβ = 20°.

and Dem

magnetizationhich the magm 180° to 60°gnetization lim80°), this val° model and

). As the magdemagnetizatiratio Tr n ar

the horizontd the verticalnce improvemand 5). tion resistan

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is 100% (ciratio is th

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placed in

is the maximon-conductingefore and aield current, d

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magnetizat

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al axis showsl axis showsment ratio or

nce improvemnt of a rotor w

ment using ircle within she ratio of flat arrangemne; 1). Underume, at a mamagnet widthmagnet lengtconstant usinnet. mprovement r


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reases in magnetizationthe magnet l

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the V-shan improvemeength ratio

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net length ro.

ength ratio vs.

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aped arrangent ratio alsdecreases. F

ngle Va vs. de

ratio vs. de

torque ratio

gement, theso decreasesurther, if the

emagnetization

emagnetization

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n

n

demagnetizatorque ratioimprovemenbecomes 90are in a trade

Next, wethe demagnfield orienteVa = 100° m

In the oblif the magneLm can bedemagnetizaVa = 100° marrangementresistance anparameter.

A list of based on a ma reference. of the demademagnetizathe ratio of value of the of non-condsum of the since the mathe current based on minfluence of the torque w

In the anaxis is the mshows the dtorque ratio.greatly redu3 with a mobtained bythrough redreduction of

On the oth

The Study

ation improvo decreases. nt ratio of 20% or less (cie-off relation investigate

netization resd magnets wh

model is less tlique magnetiet thickness te increased, ation resistanmodel offers at, so we invend torque usi

the studied mmotor model Demagnetiza

agnetization ation limit cu

the magnet’air gap’s ma

duction. The magnet torquaximum torquphase and th

magnet torquf using differewith the magnnalysis resultsmagnet lengt

demagnetizati. The demagn

uced for a momagnetic fiely increasingducing the f the magnet lher hand, in a


ement ratio Aiming for

00% or more,rcle in dotted

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and thus ce can be expa lot of latituestigated the ing the magne

magnets is gin which maation is evalulimit current

urrent. Torqus torque rati

agnetic flux dtorque of th

ue and the reue per currenhis is a motoue. In orderent magnets, net torque ratis (see Fig. 6th ratio, and ion limit currnetization limtor using mald orientationg the magn

magnet thiclength Lm). a motor in w


is improved,demagnetiza

, the torque rd line; 2.3). T

ity of improvoblique magnnet length rati

nted magnet, ehe magnet lenimprovementpected. Using

ude in the mademagnetiza

et length Lm

given in Tablagnet 1 is useuated as the rt ratio to the ue is evaluateio to the aveensity at the t

he IPMSM iseluctance tornt is about 20or model mar to clarify here we comio. 6), the horizo

the vertical rent ratio and

mit current ratgnet 2 or man angle α =

netic width ckness tm (

which magnet


, the ation ratio They

ving netic io of

even ngth t in g the agnet ation as a

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ed as rage time s the rque, 0° in ainly

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ontal axis

d the tio is agnet = 0° Wm (i.e.,

4 or

Tab

No

12345

Fig.imp

mag20°impthe chawidin th

4.Fie

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wheDr

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ble 2 Magnet

.Magnet length Lm [mm] 1.65 1.60 1.50 1.50 1.40

. 6 Magnprovement rati

gnet 5 with th is used, the

proved over tmagnetic f

ange in the tdth Wm increhe demagneti

Demaeld-Weaken

The demagnentrol (β = 8gative d-axis defined as then.

ere, Dr 80 is90 is the dem

The smaller ththe more m

istance in the


parameters. Magnet width Wm [mm] 10.75 11.1 11.8 11.8 12.7

net length ro and torque r

he magnetic fdemagnetiza

that of the mfield orientattorque ratio ases, but it isization limit c

agnetizationning Contr

etization ratio80°) decreasof the currene current pha

Cr 80 = Dr the demagne

magnetizationhe current ph

margin is givefield-weaken

Magnets for

magnetic orientation angle α [deg.] 0 0 0 20 20

ratio vs. deratio.

field orientatiation limit cumotor using mtion angle αincreases ass smaller thacurrent ratio.

n Ratol

o of the fieldses with resnt (β = 90°), aase demagne

80 / Dr 90 etization ratio

n ratio at β = 9hase demagneen to the demning control.

147

magnet length ratio 100% 97% 91% 97% 90%

emagnetization

ion angle α =urrent ratio ismagnets withα = 0°. Thes the magnetan the change

tio at

d weakeningspect to theand this ratiotization ratio

(5)o at β = 80°,90°. etization ratiomagnetization

7

n

= s h e t e

t

g e o o

) ,

o n

148

Fig. 7 demagnetizathe magneticthe Va = 1angle α = demagnetizathe demagneWhen the demagnetiza

At the macurrent is 7(Dr 90) is 080° (Dr 80)10°, the detimes.

At α = 20large demdemagnetiza80° is smalhigh.

5. MagneRatio at F

Fig. 8 shratio Cr withis 1, 2, 3, 4,orientation a(magnet lenmagnet lengindicates Crmagnetic fieusing magnemagnet lengorientation aindicates Corientation aindicates a s

At the ma4), the curimproved. Alow as 74%

The Study

shows the ation ratio Drc orientation 130° model.

0°, when tation ratio at βetization ratio

current phation ratio is ragnetic orient0 A, the dem.91%, and th) is 0.67%. I

emagnetizatio

0° with respecmagnetizing ation ratio wll, the demag

et Length Field Weake

hows the cuh respect to th and 5 in Tabangle α = 0°

ngth 100%) ingth ratio of 97r = 0.34. Oeld orientatioet 4 indicates gth ratio of 9angle α = 0°,

Cr = 0.54; angle α = 20smaller Cr = 0agnet length rarrent phase dAt the magnet% (magnet


relationshipr with respect

angle α = 0At the mag

the current β = 90° (Dr 9

o at β = 80° (hase differsreduced to 0.tation angle αmagnetizationhe demagnetizIf the current on factor is

ct to α = 0°, iresistance

when β is shifgnetization re

and Demening Cont

urrent phase he magnet leble 2. With th°, the motor ndicates Cr =7%, the moto

On the other on angle α =a smaller Cr

90% and, ththe motor uswhereas w

0°, the motor0.44. atio of 97% (mdemagnetizatt length ratio 3), and at


p between t to the curren° and α = 20

gnetic orientais 42.5 A,

90) is 0.91%,(Dr 80) is 0.7s by 10°, 87 times. α = 20°, whenn ratio at β =zation ratio at

phase differreduced to

in addition tocurrent,

fted from 90esistance rati

magnetizattrol

demagnetizangth ratio, whe magnetic f

using magn= 0.39. With

or using magnhand, with

= 20°, the mr = 0.23. Withhe magnetic fsing the magn

with the mar using magn

magnet 2, mation ratio Cof 90%, Cr idemagnetiza


the nt at 0° in ation

the and

79%. the

n the = 90° t β = rs by 0.67

o the the

0° to io is

tion

ation which

field net 1 h the net 2

the motor h the field net 3 agnet net 5

agnet Cr is

is as ation

impthe

Aor malso

6. M

Wmagmagcobfielmardiffdevsintorie

Fig.

Fig.dem


provement ratsame value a

At the demagnmore, the curo improved.

Measureme

We evaluate tgnets with gnets were pr

balt sintered d orientationrket demand ficult to usevelopment; thtered magneentation angle

. 7 Current v

. 8 Magnmagnetization r


tio Dir = 90%as magnet 1. netization im

rrent phase de

ent of Mag

the magnetic oblique orie

roduced by obmagnet withn direction. for neodymiu

e them for sherefore, weets to evalues.

vs. demagnetiza

net length rratio.

Magnets for

% (magnet 5)

mprovement raemagnetizatio

gnetic Flux

flux density entation. Thbliquely slici

h respect to tSince there

um sintered mspecial protoe used samauate the d

ation ratio.

ratio vs. cu

), Cr is about

atio Dir = 90on ratio Cr is

Density

of prototypehe prototypeng samariumthe magnetice is a largemagnets, it isotypes underarium cobalt

difference in

urrent phase

t

0% s

e e

m c e s r t n

e

Two typefield orientamagnet size width Wm =The magnecomposed oa tesla meter(w 0.75 mresolution of

Next, the rotor with mthe magneticthe rotor wamade of a diameter asdensity of th

We discusdensity meadummy statomagnetic flumagnetic fibut the maga sinusoidareducing the

Fig. 11 shthe motor bangle α = 0indicated bymagnetic flu

The magn

Fig. 9 Air ga

The Study

es of magnetsation angles: is magnet th

= 10.8 mm, aetic flux deof a magnet ar (TM-4700,

mm - t 0.28 f 21,600 (see prototype m

magnet arrangc flux density

as assembled magnetic b

the stator che air gap wasss the results asured for tor. As a resuux density, iteld orientati

gnetic flux deal wave forme torque ripplehows the air by FEA. Th

0° indicated by the broken lux densities. netic flux den

ap magnet flux


s have the folα = 0°, 20°

hickness tm =and axial lenensity measuanalyzer (MADMT), and amm F-075

Fig. 9). magnets were

gement angley was measurin a cylindric

body having core, and ths measured (sof the air gapthe rotor asult of measurt is found thon angle de

ensity distribum and is the. gap magneti

he magnetic by the solid lline are non-e

nsity of 47° t

x density meas


llowing magn°. The proto

= 1.8 mm, mangth L = 31 muring device

AD-300R, DMan ultrafine pr, DMT) wit

assembled ine Va = 130°, red. Furthermcal dummy stthe same in

he magnetic see Fig. 10).p’s magnetic ssembled in ring the air ghat the maximecreased slighution approac

hus effective

ic flux densitfield orientaline and a = energized air

to 53° and 87

suring device.


netic type

agnet mm. e is MT), robe th a

nto a and

more, tator nner flux

flux the

gap’s mum htly, ched

for

ty of ation

20° r gap

7° to

Fig.

Fig.

90°of t20°to aaxisactuden

7. C

Inaccmaghighthica cdem0.39timinve


. 10 Air gap m

. 11 Air gap m

on the horizthe stator. Th is as small a

a sinusoidal ws without theual measuremnsity of the cy

Conclusion

n this paperounting forgnetic field oh-temperaturckness tm andconstant magmagnetization9 (2.6 times) es) at α = 20°estigation of


magnet flux de

magnet flux de

zontal axis is he air gap maas 7% as com

wave from 66 effect of opement at the ylinder dumm

ns

r, we examinr field-weakorientation ofe environmed magnet widgnet volumen factor Cr at

at α = 0° de° by FEA (fin

f our prototy

Magnets for

ensity (measur

ensity (analysis

distorted by gnetic flux d

mpared with α6° to 72° on then slot. It is s

air gap mmy stator.

ned the optikening contf IPMSM dr

ent, changingdth Wm while. We obtainβ = 80° for β

ecreases to Cnite element a

ype. The dem

149

red).

s).

the open slotdensity of α =α = 0°, closehe horizontalsimilar to the

magnetic flux

imum designtrol obliqueiven under a

g the magnete maintainingned that theβ = 90°, Cr =

Cr = 0.23 (4.3analysis) and

magnetization

9

t = e l e x

n e a t g e = 3 d n

The Study of Demagnetization of the Magnetic Orientation of Permanent Magnets for IPMSM with Field-Weakening Control under Hot Temperature

150

resistance of the oblique magnetic orientation magnets IPMSM in the field-weakening control is further improved.

References [1] Nishiyama, N., and Honda, Y. 2016. “Development of

IPMSM for High Temperature Conditions Using Inclined Magnetic Field Orientation and V-Shape Magnet Arrangement.” In Proceedings of IEEJ Joint Technical Meeting on “Magnetics” and “Linear Drives” MAG-16-2010, LD-16-145, pp. 23-8. (in Japanese)

[2] Uemura, H., Nishiyama, N., and Honda, Y. 2017. “The Effeteness of Magnetic field directions of V shaped embedded magnets for IPMSM.” In Proceedings of 2017 Ann. Meet. Rec. IEEJ, V, p. 15. (in Japanese)

[3] Nishiyama, N., Uemura, H., and Honda, Y. 2017. “The Study of Highly Demagnetization Performance IPMSM under Hot Environments.” In International Conference on Electrical Machines and Systems 2017 Proceedings, 8056505.

[4] Asano, Y., Honda, Y., Takeda, Y., and Morimoto, S. 2001. “Reduction of Vibration on Concentrated Winding Permanent Magnet Synchronous Motors with Considering Radial Stress.” IEEJ Trans. on Ind. Appli. l21 (11): 1185-91. (in Japanese)

[5] Maeda, Y., Urata, S., and Nakai, H. 2016. “The Evaluation of Demagnetizing Characteristics of the Permanent

Magnet in Arbitrary Directions.” In Proceedings of 2016 Ann. Meet. Rec. IEEJ, II, pp. 124-5. (in Japanese)

[6] Akune, R., Akatsu, K., Kume, K., Yamamoto, T., and Saito, S. 2016. “The Anti Demagnetization Method for Permanent Magnet Synchronous Motor Focused on Magnetized Direction of Permanent Magnet and Basic Experiment.” In 2016 IEE-Japan Industry Applications Society Conference (JIASC2016), 3-54. (in Japanese)

[7] Peng, P., Xiong, H., Zhang, J., Li, W., Leonardi, F., Rong, C., Degner, M. W., Liang, F., and Zhu, L. 2016. “Effects of External Field Orientation on Permanent Magnet Demagnetization.” In Proceedings of IEEE Energy Conversion Congress and Exposition 2016, 7855067.

[8] Galea, M., Papini, L., Zhang, H., Gerada, C., and Hamiti, T. 2015. “Demagnetization Analysis for Halbach Array Configurations in Electrical Machines.” IEEE Trans. on Magn. 51 (9): 8107309.

[9] Kawano, S., Murakami, H., Nishiyama, N., Ikkai, Y., Honda, Y., and Higaki, T. 1997. “High Performance Design of an Interior Permanent Magnet Synchronous Reluctance Motor for Electric Vehicles.” In Proceedings of Power Conversion Conference, Nagaoka, Vol. 1, pp. 33-6.

[10] Nishiyama, N., Uemura, H., and Honda, Y. 2017. “The Optimum Design of the Magnetic Orientation of Permanent Magnets for IPMSM under Hot Environments.” In Proceedings of IEEE International Conference on Power Electronics and Drive Systems, pp. 380-5.

The Study of Demagnetization of the Magnetic Orientation ... · demagnetization of field weakening...

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