Modular Permanent Magnet Machine Based on Soft Magnetic Composite
Transcript of Modular Permanent Magnet Machine Based on Soft Magnetic Composite
8/14/2019 Modular Permanent Magnet Machine Based on Soft Magnetic Composite
http://slidepdf.com/reader/full/modular-permanent-magnet-machine-based-on-soft-magnetic-composite 1/5
ModularPermanentMagnet MachineBasedonSoft Magnetic Composite
WenOuyang*, Surong Huang**, Anne Good***, T.A. Lipo*
*Department of Electrical andComputer Engineering
University ofWisconsin-Madison
1415 Engineering Drive
Madison,WI53706
" Department ofAutomation
Shanghai University
Shanghai, 200072, P.R.China
* * B u r g e s s - N o r t o n Mfg.Co.
737 Peyton Street,
Geneva, IL , 60134
Abstract With the improvement of soft magnetic composite
(SMC) material, electric machine design i s nolonger limited to the
traditional iron lamination t e c h n o l o g y . The s i n g l e extrusion
fabrication p r o c e s s of theSMCmaterial s i m p l i f i e s construction of
machine armature core. Moreover, the isotropic material
property canbe exploited for various machine structure design,
compared with the2Dflux distribution of typical iron laminations.
In this paper, a drive system based ona novel multi phase
modular permanent magnet machine is proposed. The concentric
winding structure simplifies the stator structure with the benefit
of less end winding loss, which also offers the potential of fault
tolerant capability. The performance of the drive system is
analyzed and discussed with the simulation results provided.
Keywords Soft Magnetic Composite, Permanent Magnet
(PM), Concentric Windings, Single Phase, Multiple Phase, Fault
Tolerant
INTRODUCTION
The emergence of soft magnetic c o m po site material has
greatly changed the nature of the electrical machine
construction process. The possibility ofa "one-punch" module
reduces thework effort in lamination andstacking. Lesscopper
loss canbe achieved withthe concentric winding design dueto
the shorter end windings for the p ol e p ie ce modules.[1] The
progressive improvement of soft magnetic c o m po site (SMC)
material property as illustrated in Figure 1. The isotropic
property to create a3Dmagnetic circuit creates possibilities for
various novel electric machine designs. Someprototypes based
onSMChave been reported[2-7], with[1] illustrating typical
machine designs of surface permanent magnet motor, and [ 8 ]
small induction motors.
In this paper, novel single phase and multiphase permanent
magnet drive system based onSMCmodules are proposed and
compared. The machine stator is assembled by independent
pole pieces fabricated fromtheSMCmaterial, with each pole
piece mounted by anindependent concentric phase winding,
which also simplifies the winding efforts in machine
fabrication. The rotor structure canbe designed with surface
permanent magnet (SPM)orinternal permanent magnet (1PM)
for different application requirement.
For the single phase design, the machine winding achieves
the maximumwinding factor andminimum switching devices
at the cost of air-gap length adjustment and current
compensation for the starting and pulsating torque. For the
multiphase design, a five phase drive system is proposed with
less torque ripple and potential for the phase fault operation
capability, but at the cost of significant increase number of
switching devices in the drive circuit.
Fig. 1: Magnetic property ofSMC
I I MACHINESTRUCTURE
In order to compare the effective usage ofmachine material,
the winding factor K & is typically defined as in [ 9 ] . Ahigher
winding factor meanshigher utilization of the stator module,
which includes stator winding and stator iron volume for the
energy conversion, thus higher power density when the other
factors are same. The general expression of K,,h with
consideration ofharmonic order h is expressed as:
Kwh:::
KphK dhKXhKsh (1)
K r h . Kdh. K A h . and K ~h are factors for p i t c h , distribution, slot
opening, and skew. For the surfacePMmachine discussed in
this paper, the distribution, skew and s lot opening factors are
unity due to the concentric winding, non-skew rotor structure
andrelative small slot opening design. Thus, the winding factor
will be virtually determined by the pole pitch factor, which is
generally defined as (2) [ 9 ] :
hWzT hzTK ph s i n ( -) s i n ( )
T p2 2(2)
The quantityWenotes the concentric winding span, and - r .
is the pole pitch. For the fundamental component, the
235
S M C maeiaHCuv
--I-- -- -- a
- 4-
Authorized licensed use limited to: Chaitanya Bharathi Institute of Technology. Downloaded on July 9, 2009 at 02:54 from IEEE Xplore. Restrictions apply.
8/14/2019 Modular Permanent Magnet Machine Based on Soft Magnetic Composite
http://slidepdf.com/reader/full/modular-permanent-magnet-machine-based-on-soft-magnetic-composite 2/5
maximum w i n d i n g f a c t o r i s a c h i e v e d w h e n w i n d i n g s p a n i s
e q u a l t o t h e p o l e p i t c h , w h i c h l e a d s t o t h e s i n g l e p h a s e m a c h i n e
c o n c e p t a s i l l u s t r a t e d i n F i g u r e 2 . T h e s q u a r e w a v e o f b a c k
EMF a l s o s u g g e s t s t h e s q u a r e w a v e f o r m o f c u r r e n t s u p p l y t oa c h i e v e t h e maximum p o w e r d e n s i t y .
A
w a v e f o r m a n d t h e r e s u l t i n g m a c h i n e t o r q u e a r e p r o v i d e d i n
F i g u r e 5 f o r c o m p a r i s o n .
S I 4 4 E / 2 ~ ~ ~ ~ ~ ~ ~ ~ ~ J l l ' '- . . X . . . V . % . A . . . . . f k p L j t
XVEIL';'.'L3X'.''.'''.t=''',~~~~~~~~2c2-----------4 E ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ . E . . . L . . . g E . . . . . E .R....o ........ 2 5 . . ... - .. .......6 0 1 0 0 1 5 0 20 0 2 5 0 3M 3 5 0
F h a e Ige4 o sltt vkn
F i g . 4 : S i m u l at io n o f s q u a r e wave c u r r e n t s u p p l y a n d m a c h i n e t o r q u e
F i g . 2 : S i n g l e p h a s e s u r f a c e PMm a c h i n e c o n c e p t
H o w e v e r , t h e i n t r i n s i c s t a r t i n g p ro b le m s o f t h e s i n g l e p h a s e
PM m o t o r m a k e i t n e c e s s a r y t o a p p l y s o m e v a r i a t i o n o n t h es t a t o r t e e t h s h a p e [ 1 0 ] . One o f t h e s u g g e s t e d t e c h n i q u e s i s t o
c r e a t e a t a p e r e d a i r - g a p l e n g t h b y s h a p i n g t h e t o o t h t i p d e p t h .By m a k i n g u s e o f t h e c o g g i n g t o r q u e g e n e r a t e d b y t h ea s y m m e t r i c r e l u c t a n c e c e n t e r s a r o u n d t h e t o o t h a x i s , t h e m o t o r
c a n pass t h e z e r o t o r q u e p r o d u c t i o n p o i n t a t t h e c o s t o f
f l e x i b i l i t y i n r o t a t i o n d i r e c t i o n . F i g u r e 3 g i v e s a n e x a m p l e
d e s i g n b as ed o n t h e s i n g l e p h a s e m a c h i n e c o n c e p t w i t h t a p e r e ds t a t o r t e e t h a n d t h e c o r r e s p o n d i n g c o g g i n g t o r q u e p r o p e r t y .T h e m a c h i n e s t a t o r i s a n a s s e m b l y o f e i g h t p o l e p i e c e sf a b r i c a t e d f r o m SMC m a t e r i a l o r e v e n s t e e l l a m i n a t i o n s . T h e
a i r - g a p l e n g t h b e t w e e n r o t o r r a r e e a r t h PMs a n d s t a t o r p o l e s i s
v a r i e d f r o m 0 . 7 mm t o 1 . 3 mm.
F i g . 3 : S i n g l e ph as e m a c h i n e e x a m p l e d e s i g n a n d t h e c o g g i n g t o r q u e p r o p e r t y
When t h e PM a x e s a r e a l i g n e d w i t h t h e s t a t o r p o l e p i e c e a x e s ,w h i c h c o r r e s p o n d s t o t h e r o t o r p o s i t i o n o f 2 2 . 5 d e g r e e s , t h em a c h i n e s t i l l d e v e l o p s s i g n i f i c a n t c o g g i n g t o r q u e t o r i d e o v e r
t h e p o i n t w i t h d i f f i c u l t y i n t h e a c t i v e t o r q u e p r o d u c t i o n , w h e r e
i s u s u a l l y t h e r o t o r p o s i t i o n p o i n t f o r c u r r e n t c o m m u t a t i o n .
W i t h a r a t e d s q u a r e w a v e f o r m c u r r e n t s u p p l y , t h e m a c h i n e t o t a lt o r q u e p r o p e r t y i s s i m u l a t e d a s s h o w n i n F i g u r e 4 . A l t h o u g h
t h e a v e r a g e t o r q u e i s s i g n i f i c a n t l y h i g h e r t h a n t h e r a t e d t o r q u e
o f a t y p i c a l 3 h p i n d u c t i o n m a c h i n e ( G E - 5 K I 8 2 B C 2 1 8 A ) a t
1 7 5 5 r p m f o r t h e s a m e e f f e c t i v e m a c h i n e v o l u m e , t h e m a c h i n e
t o r q u e f l u c t u a t i o n s a n d t h e c o r r e s p o n d i n g n o i s e a n d v i b r a t i o np r o b l e m s r e d u c e i t s s c o p e o f a p p l i c a t i o n . By p u s h i n g l i m i t o f
t h e w i n d i n g f a c t o r , t h e i n t r i n s i c p u l s a t i o n p r o b l e m t h a t c o m e s
w i t h t h i s m a c h i n e s t r u c t u r e c a n b e c o m p e n s a t e d b y t h e a c t i v ec o n t r o l o n t h e c u r r e n t s u p p l y [ 1 1 ] . T h e c o m p e n s a t i n g c u r r e n t
F i g . 5 : S i m u la t i o n o f c u r r e n t c o m p e n s a t i o n a n d m a c h i n e t o r q u e
A l t h o u g h t h e m a c h i n e t o r q u e c a n b e i m pr ov e d b y c u r r e n tc o m p e n s a t i o n , t h e t o r q u e c u r v e c o n t a i n s a s ag p o i n t w h e r e t h em a c h i n e s t a t o r c u r r e n t i s i n t h e c o m m u t a t i o n p r o c e s s . By
p r o p e r d e s i g n o f t h e m a c h i n e p o l e s h a p e , t h e t o r q u e v a l u e a t
t h i s s ag p o s i t i o n c a n s t i l l b e e n h a n c e d , b u t t h i s n e c e s s i t yd e p e n d s o n t h e a p p l i c a t i o n r e q u i r e m e n t . I n m o s t c a s e s , e f f o r t sa r e u s u a l l y f o c u s e d o n t h e r e d u c t i o n o f c o g g i n g t o r q u e . W h i l e
i n t h i s c a s e , t h e c o g g i n g t o r q u e h e l p s t h e o p e r a t i o n o f m a c h i n e .
T h e c u r r e n t c o m p e n s a t i o n a l s o i n c r e a s e s t h e s t r e s s o n t h es w i t c h i n g d e v i c e s d u e t o t h e maximum v a l u e a n d t h es i g n i f i c a n t h a r m o n i c c o m p o n e n t s , w h i c h a l s o d i r e c t l y i m p a c t st h e h e a l t h o f t h e c a p a c i t o r s o n t h e DC b u s . M o r e o v e r , d u e t o t h ep u l s a t i n g MMF w h e n t h e m a c h i n e i s o p e r a t e d i n s i n g l e p h a s e
m a n n e r , t h e s y n c h r o n i s m o f t h e r o t o r a n d t h e e x c i t a t i o n p h a s e
a n g l e i s a c o nc er n . T h e i n f o r m a t i o n o n r o t o r p o s i t i o n i s
n e c e s s a r y f o r t h e p r o p e r l y a p p l i e d c u r r e n t p h a s e , w i t h t h ec u r r e n t a m p l i t u d e c o n t r o l l e d b y t h e f e e d b ac k f ro m c u r r e n t
t r a c k i n g d e v i c e s a s a common p r a c t i c e .
A s i n g l e p h a s e m a c h i n e b e n e f i t s f r o m i t s s i m p l e m a c h i n e
s t r u c t u r e b as e d o n SMC m o d u l e s . T h e p o l e p i e c e n u m b e r c a n
b e s e l e c t e d w i t h f l e x i b i l i t y f o r d i f f e r e n t p o w e r r a t i n gr e q u i r e m e n t s . From a n i n v e s t i g a t i o n o f a n e x a m p l e d e s i g n , t h eSMC b a s e d m o d u l a r s i n g l e p h a s e m a c h i n e c a n b e s h o w n t o
a c h i e v e s i g n i f i c a n t h i g h e r p o w e r d e n s i t y c o m p a r e d w i t h t h ec o m m e r c i a l i n d u c t i o n m a c h i n e . W i t h t h e l a r g e s c a l e f a b r i c a t i o nb a s e , t h e m a c h i n e co s t c a n b e f u r t h e r r e d u c e d . T h e d r i v e c i r c u i tc a n a l s o b e o p t i m a l l y i m p l e m e n t e d b y o n l y t w o s w i t c h i n gd e v i c e s . A l l t h e s e m e r i t s m a k e i t a t t r a c t i v e f o r t h e l o w c o s t
a p p l i c a t i o n s . H o w e v e r , a s m e n t i o n e d b e f o r e , t h e i n c r e a s e dc o m p l e x i t y o f c u r r e n t c o n t r o l l e r a n d t h e i n t r i n s i c m a c h i n e
t o r q u e p u l s a t i o n a n d t h e c o r r e s p o n d i n g n o i s e a n d v i b r a t i o np r o b l e m s may a l s o l i m i t i t s a p p l i c a t i o n r a n g e . T h u s , t h e
2 3 6
Authorized licensed use limited to: Chaitanya Bharathi Institute of Technology. Downloaded on July 9, 2009 at 02:54 from IEEE Xplore. Restrictions apply.
8/14/2019 Modular Permanent Magnet Machine Based on Soft Magnetic Composite
http://slidepdf.com/reader/full/modular-permanent-magnet-machine-based-on-soft-magnetic-composite 3/5
m u l t i p h a s e m od u l ar m ac hi ne s t r u c t u r e i s p r o p o s e d a n d
c o m p a r e d w i t h t h e s i n g l e p h a s e m a c h i n e .
Due t o t h e f a c t o f m o d u l a r s t r u c t u r e o f s t a t o r , e a c h m o d u l e
c a n b e w o u n d e d b y a c o n c e n t r i c w i n d i n g s e p a r a t e l y , w h i c h n o t
o n ly s i m p l i f i e s t h e l a b o r e f f o r t o n w i n d i n g s , b u t a l s o o f f e r sf l e x i b i l i t y o f m u l t i p h a s e n u m b e r a n d c o n t r o l s t r a t e g i e s . I n
F i g u r e 6 , a s t a t o r m o d u l e i s i l l u s t r a t e d b a s e d o n t h i s d e s i g nc o n c e p t . T h e m o d u l e f u r t h e r b e n e f i t s f r o m t h e SMC's
f l e x i b i l i t y o f 3D f l u x p a t h f o r i t s e x t e n s i o n o f p o l e s h o e a n d
y o k e s e c t i o n s , a s d i s c u s s e d b y o t h e r r e s e a r c h e r s . W i t h t h e s a m e
t o t a l m a c h i n e v o l u m e , t h i s s t a t o r m o d u l e c a n m a k e f u l l u s a g e o f
t h e m a c h i n e a i r - g a p s p a c e , e n h a n c i n g m a c h i n e ' s t o r q u e
p r o d u c t i o n .
F i g . 6 : S t a t o r m o d u l e c o n c e p t
I n F i g u r e 7 , a f i v e p h a s e m a c h i n e c o n c e p t i s i l l u s t r a t e db as e d o n t h e m o d u l a r m a c h i n e s t r u c t u r e . T h e t h e o r e t i c a l f l u xl i n k a g e a n d b ac k EMF c u r v e s a r e a l s o d e p i c t e d f o r t w o o f t h ep h a s e s , w i t h 2 t 5 e l e c t r i c a l a n g l e s h i f t b e t w e e n p h a s e s . T h e
f u n d a m e n t a l w i n d i n g f a c t o r 0 . 9 5 1 c a n b e d i r e c t l y o b t a i n e d
f r o m ( 2 ) .
H C S ~ ~ ~ ~ ~ ~ ) 4A - ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0. .....
F i g 7 : SxpLe iepaesraeP ahnocp
A l t h o u g h t h e w i n d i n g f a c t o r i s n o t a s h i g h a s t h e f u l l p i t c hs i n g l e p h a s e m a c h i n e s u g g e s t e d b e f o r e , t h e m a c h i n e c a n b e
o p e r a t e d m o r e e a s i l y w i t h a c c e p t a b l e p o w e r d e n s i t yp e r f o r m a n c e . ( 3 ) - ( 6 ) d e s c r i b e t h e m a c h i n e ' s g o v e r n i n g
e q u a t i o n s o f g e n e r a l o p e r a t i o n .
[ v ] = [ e ] + [ r ] [ i ] + d [ A ]dt
( 3 )
w h e r e v , e , i , i d e n o t e s t h e v e c t o r o f p h a s e t e r m i n a l v o l t a g e ,b a c k EMF ( e m f ) , c u r r e n t , a n d f l u x l i n k a g e .
[ i ] = I L I [ i d ( 4 )
L 1 l L 1 2 L 1 3 L 1 4 L 1 5
L 2 1 L 2 2 L 2 3 L 2 4 L 2 5[ L ] = L 3 1 L 3 2 L 3 3 L 3 4 L 3 5 ( 5 )
L 4 1 L 4 2 L 4 3 L 4 4 L 4 5
L 5 1 L 5 2 L 5 3 L 5 4 L 5 5 -
B a s e d o n t h e c l a s s i c e n e r g y c o n v e r s i o n , t h e m a c h i n e t o r q u e
a n d s p e e d p r o d u c t i o n e q u a l s t h e p o w e r i n p u t f r o m t h e i n v e r t e rs i d e a s ( 6 ) , i f t h e r e s i s t a n c e a n d o t h e r l o s s e s a r e n e g l e c t e d .
T e * m= [ e ] [ i ] ( 6 )
I n t h i s s t u d y , t w o t y p i c a l r o t o r s t r u c t u r e s , s u r f a c e p e r m a n e n t
m a g n e t ( S P M ) a n d i n t e r n a l p e r m a n e n t m a g n e t ( I P M ) , a r ed i s c u s s e d , a s t h e s e t w o t y p i c a l m a c h i n e t o p o l o g i e s i l l u s t r a t e d i nF i g u r e 8 . T h e SP M m a c h i n e s a r e w id el y u se d i n i n d u s t r ya p p l i c a t i o n s f o r i t s l o w c o s t a n d h i g h p e r f o r m an c e , b u t w i t h t h ed i f f i c u l t i e s i n t h e e x p e n d e d s p e e d o p e r a t i o n f o r i t s l i m i t e d f i e l d
w e a k e n i n g c a p a b i l i t y , d u e t o t h e f a c t t h e f l u x f r o m t h e PMs
c a n n o t b e t u r n e d o f f a n d t h e c u r r e n t c a p a b i l i t y l i m i t e d b y t h es u p p l y . H o w e v e r , t h e IPM m a c h i n e e x h i b i t s i m p r e s s i v e f i e l d
w e a k e n i n g c a p a b i l i t y f o r t h e r e l a t i v e l y h i g h e r m a c h i n e
i n d u c t a n c e d u e t o t h e l e s s e f f e c t i v e a i r - g a p l e n g t h .
( a ) ( b )F i g . 8 : S i x p o l e f i v e p h a s e m a c h i n e c o n c e p t . ( a ) S P M . ( b ) IP M
F o r t h e SP M r o t o r d e s i g n a s i l l u s t r a t e d i n F i g u r e 8 , t h ei n d u c t an c e m a t r i x L e x h i b i t s l o w c o u p l i n g b e t w e e n p h a s e s d u e
t o t h e l o w m u t u a l i n d u c t a n c e , w h i c h b e n e f i t s d e a l i n g w i t h
p h a s e f a u l t o p e r a t i o n . T h i s t y p i c a l d e s i g n l e a d s t o t h e L m a t r i x
( m H ) a s d e s c r i b e d i n ( 7 ) s i m u l a t e d b y s o f t w a r e p a c k a g e
M a x w e l l . O n t h e d i a g o n a l o f t h e m a t r i x L i n ( 7 ) , t h e s e l fi n d u c t a n c e e x h i b i t s q u i t e s i m i l a r v a l u e s d u e t o t h e l a r g e a i r g a p
t a k e n b y t h e P M s . W h i l e f o r t h e o f f - d i a g o n a l t e r m s , t h e m u t u a l
i n d u c t a n c e s a r e r e l a t i v e l y c o u p l e d s t r o n g e r w i t h t h e a d j a c e n tp ha s e w i n d i ng s f o r t h e s h o r t e r f l u x p a t h , a l t h o u g h t h i s k i n d o f
c o u p l i n g i s s t i l l w e a k w i t h t h e c o u p l i n g c o e f f i c i e n t o f 0 . 2 3 6 a n d
0 . 1 7 4 f o r t h e a d j a c e n t a n d n o n - a d j a c e n t p h a s e c o u p l i n g .
7 . 8 9 1 . 8 91 . 8 9 8 . 1 3
[ L S P M ] = 1 . 4 2 2 . 0 9
1 . 4 5 1 . 5 0
1 . 9 7 1 . 4 6
1 . 4 22 . 0 9
8 . 4 2
2 . 1 4
1 . 5 9
1 . 4 51 . 5 0
2 . 1 4
8 . 4 8
2 . 2 2
1 . 9 71 . 4 6
1 . 5 9
2 . 2 2
8 . 4 7
( 7 )
W i t h a n i n t e r n a l p e r m a n e n t m a g n e t d e s i g n f o r t h e r o t o r
s t r u c t u r e , t h e e f f e c t i v e a i r - g a p l e n g t h c o u l d b e r e d uc e d
s i g n i f i c a n t l y , r e s u l t i n g i n a r e l a t i v e l y h i g h e r m a c h i n e
i n d u c ta n c e m a t r i x a s s h o w n i n ( 8 ) . I t c a n b e o b se rv e d t h a t t h es e l f - i n d u c t a n c e s o f t h e IPM r o t o r d e s i g n ar e s i g n i f i c a n t l yi n c r e a s e d . M o r e o v e r , t h e s e l f i n d u c t a n c e v a r i e s n o t i c e a b l y d u e
t o t h e d - q a x i s e f f e c t , w h i c h c a n b e n e g l e c t e d i n t h e SP M r o t o rs t r u c t u r e . T h e d - a x i s i n d u c t a n c e L q = 2 6 . 2 2 m H , w i t h L d =
2 3 7
Authorized licensed use limited to: Chaitanya Bharathi Institute of Technology. Downloaded on July 9, 2009 at 02:54 from IEEE Xplore. Restrictions apply.
8/14/2019 Modular Permanent Magnet Machine Based on Soft Magnetic Composite
http://slidepdf.com/reader/full/modular-permanent-magnet-machine-based-on-soft-magnetic-composite 4/5
1 8 . 1 ImH f o r t h i s t y p i c a l d e s i g n . T h e a d j a c e n t p h as e c ou pl in g
i s q u i t e s i m i l a r w i t h SP M f o r t h e c o u p l i n g c o e f f i c i e n t 0 . 2 6 6 ,a l t h o u g h t h e i nd u c ta n ce v a l u e i s n e a r l y t r i p l e d . T h e c o u p l i n g
b e t w e e n t h e n o n- a d j a ce n t p h a se s i s f u r t h e r r e d u c e d t o a r o u n d
0 . 1 6 4 .
1 8 . 1 1
5 . 1 8
[ L I P M ] = 3 . 4 1
3 . 2 8
5 . 2 0
5 . 1 8
2 1 . 0 1
6 . 7 1
3 . 9 0
3 . 9 8
3 . 4 1
6 . 7 1
2 3 . 9 7
8 . 7 5
3 . 8 2
3 . 2 8
3 . 9 0
8 . 7 5
2 4 . 7 1
7 . 4 2
5 . 2 0
3 . 9 8
3 . 8 2
7 . 4 2
2 1 . 6 6
( 8 )
A s d i s c u s s e d b e f o r e , i t i s d i f f i c u l t t o o p e r a t e SP M m a c h i n e i n
t h e e x t e n d e d s p e e d r a n g e d u e t o t h e l i m i t e d f i l e d w e a k e n i n g
c a p a b i l i t y o f t h i s m a c h i n e d u e t o t h e l i m i t e d c o n t r o l l a b i l i t y o f
f l u x w h i c h d e p e n d s o n t h e i n d u c t a n c e a n d c u r r e n t p r o d u c t L i .
W i t h a n IPM d e s i g n , t h e hig he r i n d u c t a n c e m a k e s i t f e a s i b l e t o
o b t a i n a n e x t e n d e d s p e e d o p e r a t i o n i n f i e l d w e a k e n i n g r a n g e .
M o r e o v e r , t h e l o w e r a i r g a p f l u x d i s t r i b u t i o n f a v o r s IPMm a c h i n e f o r i n t h e h ig h s pe ed r a n g e a s s h o w n i n F i g u r e 9 . I nt h e s e t w o t y p i c a l SP M a n d IPM r o t o r d e s i g n s , r a r e e a r t h( N d F e B ) i s u s e d f o r t h e s i m u l a t i o n . T h e t h i c k n e s s o f PMs i n t h eSP M d e s i g n v a r i e s f r o m 3.5mm t o 6mm, w h i l e f o r I P M , 3mmPMs a r e i n s e r t e d i n t o t h e s l o t s . T h e a v e r a g e a i r g a p f l u x d e n s i t yp e r p o l e o f IPM d e s i g n i s n e a r l y h a l v e d c o m p a r e d w i t h t h eSP M d e s i g n . Due t o t h e e x i s t e n c e o f s a t u r a t e d b r i d g e s o n t h er o t o r s i d e s t r u c t u r e , s i g n i f i c a n t f l u x b y p a s s e d t h e m a i n f l u xp a t h a s p u r e l y l e a k a g e . To d e s i g n a n IPM r o t o r w i t h s p e c i f i e dd - q a x i s r e a c t a n c e u n d e r w i d e r a n g e o p e r a t i o n i s s t i l l ac h a l l e n g i n g t a s k f o r t h e v a r i a b l e l o a d c o n d i t i o n s a n d
c o r r e s p o n d i n g s a t u r a t i o n l e v e l . T h e s a t u r a t i o n b r i d g e s a r ed e s i g n e d w i t h c o n s i d e r a t i o n s f o r b o t h e l e c t r o m a g n e t i c a n d
m e c h a n i c a l s t r e s s e s , e s p e c i a l l y w h e n t h e m a c h i n e i s o p e r a t e d i nt h e h i g h s p e e d r a n g e .
1 - - - - - - r - - - - - - -- - t t - - - - - - T - - - -- ----- T - - - - - T - -- - - - - - - - T
O . S 0 l t - - - - - - - u - - - - + 5 - o ; \ - - - - - - - - - - - l -- - - - - - - - - -
n° ----- X---t--.-i-1
-L - --------- -X.
S M r d a f l u d e n s t5 -PM r a d r i a l f l u x e n s [ l y
0 5 1 ' 1 0 0 C C 1 5 0 2 2 0 0 1 2 5 0 C 3 0 0 1 3 5 0 2
a n g l e ( m q e c h )
F i g . 9 . A i r g a p r a d i a l f l u x d i s t r i b u t i o n f o r SPM a n d IPM
One o f t h e m a i n m e r i t s o f t h i s m o d ul ar m a ch i ne s t r u c t u r e i s
i t s f a u l t t o l e r a n t c a p a b i l i t y a n d e a s y r e p l a c e m e n t o f m o d ul es .
T h e c o n c e n t r i c w i n d i n g i s w o u n d o n e ac h s t a t o r SMC m o d u l e ,
r e s u l t i n g i n a n i n d e p e n d e n t c o n t r o l u n i t w i t h t h e f e a t u r e o f
r e p l a c e m e n t i n c as e o f u n i t f a i l u r e . E a c h u n i t i s a l s o c o n t r o l l e d
b y t h e i n d e p e n d e n t s w i t c h i n g d e v i c e s , w i t h t h e o p t i o n o f
m o u n t i n g c o n t r o l m o d u l e w i t h t h e m a c h i n e m o d u l e a t
a c c e p t a b l e c o s t . I n n o r m a l o p e r a t i o n , t h e m a c h i n e ' s s q u a r e
w a v e c u r r e n t i s i n p h as e w i th t h e b a c k EMF. I n ca s e o f p h as e
w i n d i n g f a i l u r e , a c o m p e n s a t i o n i mp le m e nt ed b y c o n t r o l
s t r a t e g y h e l p s t o m a i n t a i n t h e m a c h i n e t o r q u e .
M o s t o f t h e p h a s e f a u l t s a r e d i r e c t l y r e l a t e d w i t h t h ew i n d i n g f a i l u r e , i . e . , o p e n c i r c u i t a n d s h o r t c i r c u i t . O p e n c i r c u i t
i s q u i t e common f o r t h e t e r m i n a l c o n n e c t i o n f a i l u r e , a n d a l s o ,
t h e s w it c hi n g d e v i c e f a i l u r e . I n F i g u r e 1 0 , t h e f i v e - p h a s e SP Mm a c h i n e w i t h d i f f e r e n t o p e n c i r c u i t c a s e s a r e s i m u l a t e d .G e n e r a l l y , t h e a v e ra ge t or q ue i s d i r e c t l y p r o p o r t i o n a l t o t h ep h a s e n u m b e r i n s e r v i c e w i t h t h e s a m e c o n t r o l s t r a t e g ya s s u m e d f o r t h e n o r m a l o p e r a t i o n . I t i s a common p r a c t i c e t ob o o s t t h e t o r q u e l o s s b y a p p l y i n g c o m p e n s a t i n g c u r r e n t i n t h en o r m a l p h a s e s .
I
Ii
6~~~~~~~~
I ' I daetp e f
4 ---- -- - - - - -
- ---
-- -
l1'~~~~~~~~-----
-z -- I - -
~ ~ ~ ~ ~ ~ I - - - - I - - - -
1 2 - -- - - - - -- - - - r -- - - - - -- -- -- -- -- r - -- - - - - -- T - - -- - - - - - T - - -- - - - - - - - - - -- - - - - - -T
i\ _ f) < < ¢ /5,' % _ S' 1 ~ - --
l~~~~~~~~Tolacnphasel lo s
. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ T o n.-oae p h a e l o s s , ,0_ +______L_____X_L_______L_______L___
4 0 6 0 8 0ror p g s
1 4 0 lb 0 Th
P e g r
F i g . 1 0 : S q u a r e w a v e p h a s e c u r r e n t a n d m a c h i n e t o r q u e u n d e r v a r i o u s o p e n
c i r c u i t f a i l u r e s
H o w e v e r , w h e n t h e w i n d i n g f a i l u r e i s s h o r t c i r c u i t e d ,w h i c h i s u s u a l l y r e l a t e d w i t h t h e i n s u l a t i o n d e f e c t , i t i s s t i l l a
t o u g h t a s k t o m i t i g a t e t h e f a i l u r e f o r t h e h u g e c u r r e n t
c i r c u l a t i n g i n t h e s h o r t e d w i n d i n g . W i t h t h e IPM d e s i g n , i t i s
p o s s i b l e m a k e u s e o f t h e s p e c i f i c a l l y i n j e c t e d c u r r e n t o f t h e
n o r m a l p ha s e w i n d i ng s t o r e d u c e t h e f l u x l i n k a g e o f t h e s h o r t e d
2 3 8
11
Authorized licensed use limited to: Chaitanya Bharathi Institute of Technology. Downloaded on July 9, 2009 at 02:54 from IEEE Xplore. Restrictions apply.
8/14/2019 Modular Permanent Magnet Machine Based on Soft Magnetic Composite
http://slidepdf.com/reader/full/modular-permanent-magnet-machine-based-on-soft-magnetic-composite 5/5
w i n d i n g . T h u s , t h e f a i l u r e c o u l d b e t o l e r a t e d a n d t h e m a c h i n e
c a n s t i l l b e o p e r a t e d u n d e r l i m i t e d c o n d i t i o n s .
I I I . CONCLUSION
I n t h i s p a p e r , a n o v e l m o d u l a r PMm a c h i n e w i t h f a u l t t o l e r a n tc a p a b i l i t y i s d i s c u s s e d . T h e s i n g l e p h a s e d es ig n c an m a k e f u l l
u s a g e o f t h e m a c h i n e m a t e r i a l f o r i t s h i g h e s t w i n d i n g f a c t o r , b u t
i t i s v u l n e r a b l e t o s t a r t i n g p r o b l e m s w h i c h c a n n o t b e a v oi d e d
b y n o r m a l m a c h i n e d e s i g n . T h e m a c h i n e c a n b e o p e r a t e d w i t h at r a d e - o f f b e t w e e n s p e c i a l l y d e s i g n e d a i r - g a p l e n g t h a n d
c o m p l e x i t y o f t h e c o n t r o l c i r c u i t . T h u s , t h e m u l t i - p h a s em o d u l a r c o n c e p t i s p r o p o s e d f o r t h e a p p l i c a t i o n s r e q u i r e f a u l t
t o l e r a n t c a p a b i l i t y w i t h c o m p a r a b l e p o w e r d e n s i t y . A f i v ep h a s e m o d ul ar m a ch in e w i t h SP M a n d IPM r o t o r s t r u c t u r e i s
s t u d i e d . From t h e p r e l i m i n a r y s i m u l a t i o n r e s u l t s , 5 p h a s e
m o d u l ar m a c h in e e x h i b i t s s a t i s f a c t o r y t o r q u e c a p a b i l i t y b o t h i n
n o r m a l o p e r a t i o n c o m p a r e d w i t h a t y p i c a l 3 H I P i n d u c t i o nm a ch in e a nd u n d e r a f a u l t c o n d i t i o n w i t h o n e o r t w o p h a s e l e gl o s s . T h e p r o t o t y p e m a c h i n e i s u n d e r c o n s t r u c t i o n . T h e t e s t i n gr e s u l t s w i l l b e r e p o r t e d i n a f u t u r e p a p e r .
P o w e r E l e c t r o n i c s , M a c h i n e s a n d D r i v e s , 2 0 0 2 . I n t e r n a t i o n a l C o n f e r e n c e ,
J u n e 2 0 0 2 , p p . 6 4 4
[ 7 ] J . C r o s a n d P . V i a r o u g e , "New s t r u c t u r e s o f po l y ph as e c l a w - p o l e
m a c h i n e s " , I n d u s t r y A p p l i c a t i o n s C o n f er e n ce , 3 7 t h I A S A n n u a l M e e t i n g ,
O c t . 2 0 0 2 , p p . 2 2 6 7 , v o l . 4[ 8 ] R . Q u , G . B . K l i m a n , a n d R . C a r l , " S p l i t - p h a s e c l a w - p o l e i n d u c t i o n
m a c h i n e s w i t h s o f t m a g n et i c c o m po s i te c o r e s " , I n d u s t r y A p pl ic at io n sC o n f e r e n c e , 3 9 t h I A S A n nu al M e e t i n g , O c t . 2 0 0 4 , p p . 2 5 1 4 , v o l . 4
[ 9 ] T . A . L i p o , " I n t r o d u c t i o n t o AC M a c h i n e D e s i g n " , ( b o o k ) , U n i v e r s i t y o f
W i s c o n s i n , 2 0 0 4 .
[ 1 0 ] S . B e n t o u a t i , Z . Q . Z h u, a nd D . H o w e , " I n f l u e n c e o f d e s i g n p a r a m e t e r s o n
t h e s t a r t i n g t o r q u e o f a s i n g l e - p h a s e PM b r u s h l e s s DC m o t o r , " M ag n e t ic s ,
IEEE T r a n s a c t i o n s o n , v o l . 3 6 , p p . 3 5 3 3, 2 0 0 0 .
[ 1 1 ] T . M . J a h n s , Wen L . S o o n g , " P u l s a t i n g T o r q u e M i n i m i z a t i o n T e c h n i q u e s
f o r P e r m a n e n t M a g n e t AC M o t o r D r i v e s - A R e v e w " , I n d u s t r i a lE l e c t r o n i c s , IEEE T r a n s a c t i o n s o n , v o l . 4 3 , p p . 3 2 1 , A p r i l , 1 9 9 6 .
[ 1 2 ] B . A . W e l c h k o , J . W a i , T . M . J a h n s , T . A . ; L i p o , , " M a g n e t f l u x c o n t r o l o f
i n t e r i o r PM m a c h i n e d r i v e s f o r i m p r o v e d r e s po n s e t o s h o r t - c i r c u i t f a u l t s " ,I A S 2 0 0 4 , IEEE c o n f e r e n c e , V o l u m e 1 , p p . 3 . 2 0 0 4 .
APPENDIX5 p h a s e SP M m a c h i n e p a r a m e t e r s
P a r a m e t e r s IM ( G E / 3 H P ) 5 P h a s e SP M M o t o r
OD 190mm 120mm
I D 120mm 72mm
RPM 1 7 5 0 1 8 0 0
M a c h i n e L en g t h 7 0 mm ( i r o n ) / 15 0 mm ( f u l l ) 140mm
T o r q u e ( T ) 1 1 . 8 7 N m 1 3 . 2 6 N m
E f f e c t i v e V o l u m e 4 . 2 5 2 9 x I 0 3 m 3 1 . 5 8 3 4 x 0 - 3 m 3
T o r q u e D e n s i t y 2 . 7 9 1 x I 0 3 N m / m 3 8 . 3 7 4 x I 0 3 N m / m 3
C o g g i n g T o r q u e 0 3 . 0 1 % o f r a t e d
T o r q u e D e n s i t y R a t i o 5 ph as e PM / IM = 3 . 0
REFERENCE
[ 1 ] L . 0 . H u l t m a n a n d A . G . J a c k , " S o f t m a g n e t i c c o m p o s i t e s - m a t e r i a l s a n d
a p p l i c a t i o n s , " 2 0 0 3 . I E M D C ' 0 3 , v o l . 1 , p p : 5 1 6 , J u n e 2 0 0 3.
[ 2 ] A . J a c k , " E x p e r i e n c e w i t h u s i n g s o f t m a g n e t i c c o m p o s i t e s f o r e l e c t r i c a lm a c h i n e s " , New M a g n e t i c M a t e r i a l s - B o n d e d I r o n , L a m i n a t i o n S t e e l s ,S i n t e r e d I r o n a n d P e r m a n e n t M a g n e t s , I E E C o l l o q u i u m o n 2 8 , May1 9 9 8 p p : 3 / 1 - 3 / 4 .
[ 3 ] A . G . J a c k , B . C . M e c r o w , C . P . M a d d i s o n , a n d N . A . W a h a b , " C l a w p o l ea r m a t u r e p e r m a n e n t m a g n e t m a c h i n e s e x p l o i t i n g s o f t i r o n p o w d e rm e t a l l u r g y , " E l e c t r i c M a c h i n e s a n d D r i v e s C o n f e r e n c e R e c o r d , 1 9 9 7 ,IEEE I n t e r n a t i o n a l , p p . 1 8 - 2 1 , May 1 9 9 7 .
[ 4 ] A . G . J a c k , B . C . M e c r o w , P . G . D i c k i n s o n , D . S t e p h e n s o n , J . S . B u r d e s s ,N . F a w c e t t , a n d J . T . E v a n s , " P e r m a n e n t - m a g n e t m a c h i n e s w i t h
p o w d e r e d ir o n c o r e s a n d p r e p r e s s e d w i n d i n g s , " I n d u s t r yA p p l i c a t i o n s , IEEE T r a n s a c t i o n s o n , v o l . 3 6 , p p . 1 0 7 7 , 2 0 0 0 .
[ 5 ] Y . G . G u o , J . G . Z h u , P . A . Wat t e r s o n , a n d W. Wu, " C o m p a r a t i v e s t u d y o f
3D f l u x e l e c t r i c a l m a c h i n e s w i t h s o f t m a g n e t i c c o m p o s i t e c o r e s " , I n d u s t r yA p p l i c a t i o n s C o n f e r e n c e , 2 0 0 2 . 3 7 t h I A S A n n u a l M e e t i n g , p p . 1 1 4 7 v o l . 2
[ 6 ] B . C . M e c r o w , A . G . J a c k , D . J . A t k i n s o n , P . G . D i c k i n s o n , a n d S .
S w a d d l e , " H i g h t o r q u e m a c h i n e s f o r p o w e r h a n d t o o l a p p l i c a t i o n s " ,
2 3 9
Authorized licensed use limited to: Chaitanya Bharathi Institute of Technology. Downloaded on July 9, 2009 at 02:54 from IEEE Xplore. Restrictions apply.