Study of Radial Forces of Permanent Magnetic Synchronous Motor
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Transcript of Study of Radial Forces of Permanent Magnetic Synchronous Motor
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8/9/2019 Study of Radial Forces of Permanent Magnetic Synchronous Motor
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Study of Radial Forces of Permanent Magnetic
Synchronous Motor
Claudia Martis Florin Pop Piglesan
Florin Jurca Claudiu Oprea
Universitatea Tehnica Cluj!apoca" Romania
claudia#martis$emd#utcluj#ro florin%&'(pop$yahoo#com
fjurca$mail#utcluj#ro Claudiu#Oprea$mae#utcluj#ro
Abstract The present work aims to show an comparative study of the radial forces behavior
analysis of a PMSM. For this work we used a single topology, an PMSM with ! slots and " pole pairs. To
analy#ed the radial forces, we have changed the airgap dimension, magnet shape and stator windings. The
radial forces delivered by the simulations with $%mag Studio and $%mag &esigner are e'ported in Math(ab
to process the results.
). )*T+&-T)*
Recent developments in rare earth permanent magnet )PM* materials and po+er electronics have created ne+
opportunities for design construction" and application of permanent magnet synchronous motors )PMSMs*# The
PMSMs are preferred over other motors used for ac servo drives due to their high efficiency" high tor,uetocurrent
and tor,ue -tovolume ratios" compact structure" and fast dynamic response# These motors are adopted in several
residential and industrial applications# .o+ever" many of such applications re,uire minimum tor,ue ripple" and
reduced vi/ration and acoustic noise#
Servo motor technology has moved in recent years from conventional 0C or t+ophase 1C motors drives to
ne+ maintenancefree /rushless three phase PMSM drives for motor applications +here ,uic2 response" light
+eight" and large continuous and pea2 to,ues are re,uired# The tor,ue produced /y these machines has a pulsating
component" +hich varies as a function of the rotor position" in addition to the dc component#
The tor,ue pulsation are 2no+n as tor,ue ripple# The shape of the tor,ue +aveform" thus" the fre,uency
content of the +aveform are influenced /y several factors related to motor design and construction# 1 conse,uence
of introducing PMs in the rotor is tor,ue pulsation even in the a/sence of any stator e3citation" this tor,ue is 2no+n
as cogging tor/ue#
The harmonics in the 45MF due to design imperfections also introduce tor,ue pulsations# The tor,ue ripple
content in PMSMs must /e improved through cogging tor,ue and 45MF harmonics reduction for smooth operation
of the motor#
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected] -
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Mechanical vi/ration and noise is mainly due to /earings" their defects" journal ovality" sliding contacts" /ent
shaft" rotor un/alance" shaft misalignment or rotor eccentricity" couplings etc# The rotor should /e precisely
/alanced as it can significantly reduce the vi/ration# The rotor un/alance causes rotor dynamic vi/ration and
eccentricity" +hich in turn results in noise emission from the stator" rotor" and rotor support structure# 1gain" the
rotor eccentricity causes un/alanced magnetic pull in the airgap that leads to+ard vi/ration#
)). +0&)0(F+1S)*PMSMS
The acoustic noise in PM machines is lo+er compared to s+itched reluctance and induction machines" yet
,uieter performance is desired in automotive and ro/otics applications# !oise and vi/ration of the electromagnetic
origin dominates in lo+ to medium po+er PM machines# The electromechanical energy conversion due to an
interaction /et+een the magnetic fields of PMs and armature conductors ta2es place in the airgap of these
machines# 1s a result of this interaction a strong electromagnetic force field e3ists /et+een the rotor magnets andthe stator teeth# This force field can /e decomposed into tangential and radial force components at any point in the
airgap#
The radial force density or pressure can /e +ritten as6
)%*
+here 47nand 47tare the normal and tangential components of the airgap magnetic field density# 1s the tangentialcomponent is much smaller than the normal component of the airgap magnetic field density" the magnetic pressure
results as6
)&*
The airgap magnetic flu3 density can /e +ritten as6
( ) ( ) ( )[ ] ( )t,Bt,Bt,B rsn += )'*
+ith 4s)8"t*94r)8"t* the stator9rotor magnetic field density for uniform airgap" as function of angle and time" and
:7)8* the relative permeance of the airgap#
The stator magnetic field density of a threephase symmetrical +inding fed +ith a /alanced current system
)considering only the fundamental of the supply source* can /e +ritten as6
( ) ( ) ( )[ ]tBtBtp tnrmp ""&
%"
&&
;
=
( ) ( )
0
2n
rmp2
tBtp
,
,
( ) ( )
=
=
1k6
ss ptcosBt,B
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))). 1(1T+M02*1T) 0*0(3S)S -S)*2 $%M02
The machine under study is a PMSM +ith & stator slots and B rotor poles t+olayer +inding" are analyGed for
/oth ;#@mm and %mm airgap length )Fig#%*#The main geometrical data of the machine are given in Ta/le H#
T14I5
M1H!5OM5TRHC1I01T1OFT.5STU0H50M1C.H!5S
a* /*Fig# %# & slots ' pole pairs field lines for6 a* % mm /* ;#@ mm
From fig#% it can /e deducted that the distri/ution is uniform in /oth cases#The flu3 density distri/ution is
comparatively analysed at tK;#;%B< s#
a* /*
Fig# & slots ' pole pairs9'
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The magnetic flu3 density for the motor +ith % mm airgap siGe has a ma3imum value of %#;@ T and for the
motor +ith ;#@ mm airgap siGe has a ma3imum value of %#& T#
Fig# ' Magnetic Flu3 0ensity
The airgap magnetic field density provides valua/le information on the electromagnetic machine /ehavior
)electromagnetic tor,ue" cogging tor,ue" /ac2emf" etc* /ut also on other aspects as thermal and vi/roacoustics#
The airgap magnetic field distri/ution for load regime" as +ell as the electromagnetic tor,ue developed /y the
motor is presented in Fig#
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The Space harmonic components of !odal Forces are given in Fig# @#
Fig# @# Space harmonics spectrum of the radial forces !oIoad regime
1 richer harmonic content can /e noticed for the ;#@ mm airgap length machine" +ith a higher value of the
amplitude and more harmonics" the % thand &Eth is missing from the % mm airgap length" in conclusion +ith a
smaller airgap length" +e have to,ue ripples and increased harmonics#
1nother regime of this study" that +e collect results is rated load# Hn this regime +e can notice that the
.armonic 1mplitude is smaller" than no load regime" and on the % mm airgap length is present the % thand &Eth
harmonic" +hich are missing from noload regime#
Fig# B# Space harmonics spectrum of the radial forces RatedIoad regime
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The time depending +aveform of the radial force for a virtual pro/e mounted on the stator tooth having the
coordinates )&@#@e'" ;* is given in Fig# " for /oth ;#@ and % mm airgap length#
Fig# # Time harmonic spectrum of the radial forces !oIoad regime
Hn Ta/le & is represented a comparative values of 1mplitude and Fre,uency /et+een the airgap length results#
Ne can notice that Time .armonics results has no impact and no major different values /et+een this part of
simulation +or2#
Ta/le & 1mplitude and Fre,uency results
H
Time 7armonics
0irgap lenght 8,9 mm 1irgap lenght % mm
Fre,uency 1mplitude Fre,uency 1mplitude
'
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0ifferent to space harmonics" the .armonic 1mplitude has different values for /oth regimes of +or2# For %
mm airgap length ratedload " the amplitude is smaller than the other regime /ut the same length and for ;#@ mm
airgap length ratedload " the amplitude is /igger than noload regim#
Fig# D# Time harmonic spectrum of the radial forces RatedIoad regime
1nother part of our +or2" represents the magnet shape# Hn our simulation +e change the edge of magnet to
study the influence of them on space and time harmonics# The simulation is made only for ;#@ airgap length no
load regime# Fig# E represents the shape of the magnets that +e used in our test simulation#
a* /*
Fig# E# Magnetic Shape a* rectangular /* Oval
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The Space harmonic components of !odal Forces are given in Fig# %;#
Fig# %;# Space harmonics spectrum of the radial forces !oIoad regime +ith Oval Magnets
From the spectrum +e can deduced that the harmonics have the same order li2e the other results"
+ith rectangular magnets /ut the amplitude on the % st" @thand %%th order is a little /it /igger comparative
+ith the others results#
The Time harmonic components of !odal Forces are given in Fig# %%#
Fig# %%# Time harmonic spectrum of the radial forces !oIoad regime +ith Oval Magnets
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@#