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Investigation the effect of the axial
channel rotor to the out put
performance in Inset Permanent
Magnet Synchronous Machine
J.M. Ling Member of IEEE and Tajuddin Nur
Department of Electrical Engineering Southern
Taiwan University (STUT)- Taiwan
1. Introduction
2. Rotor Structure and Magnetic Theory
3. Object of Study.
4. FEMM for PMSM’s Simulation
5.Simulation Result
6. Conclusion
• Abstract
• Sometimes, for special purpose or any reason
an electrical machine is to be constructed to
have some holes or axial hollows in it’s rotor
core. The aim of this paper is to investigate
the effect of axial hole in the rotor core of the
Inset Permanent Magnet Machine ( Inset
PMSM) to the magnetic flux density in the air
gap .
• In this paper, the length and type the of
axial length in the rotor core is
determined. The Inset – PMSM is used to
investigate has eight poles and radial
pole structure type. At the beginning,
the rotor core is reconstructed, by
making some holes in rotor core.
To be continued
• The type of the holes has five sides each
as shown in thin this paper. Then it is
simulated using FEMM to investigate
the relation between magnetic flux
density of every magnet poles in the air
gap, magnetic flux losses in the rotor
teeth, density magnetic flux in the rotor
core surface and torque of the machine.
• The simulation result ( using FEMM 4.2)
then we compared to the conventional
rotor structure. From the simulation we
found that that the magnetic flux
density per pole in air gap of
reconstruction rotor is remain constant
or drop about 5% compared to the
conventional rotor core has.
•
1. Introduction
• Permanent Magnet Synchronous Machine
(PMSM) has been widely studied since the last
ten years [1]-[3]. The PMSM has advantages
such as high power density and realibility,
good efficiency, their reduced maintenance
costs. J.F Gieras (2010) has explained about
the cost production of permanent magnet
machine [2].
• Sometimes, to apply the electric
machine special purpose, any or
some electrical machine must be
constructed to have any special
design according to the system
where the electrical machine should
be applied.
• In this paper will discuss about the
axial channel in the rotor core of
inset permanent magnet electrical
machine. There are some papers has
studied about permanent magnet
electrical machine. In papers [4]-[6],
have
studied
about
rotor
modification using holes.
• M.S Widyan [7], explained the
relation between holes in rotor core
to related to the rotor mass. S.
Wang et al. [8], studied about the
relation between holes under the
rotor teeth to the rotor reactance.
Rotor Structure and Magnetic Theory
• Most of conventional Inset PMSM
have magnets mounted on the rotor
surface facing the air gap. In inset
PMSM, the magnets are placed at
rotor outer diameter, and between
poles there are any “rotor teeth”
and create circumferential saliency,
as shown in Fig. 1A and 1B.
•
(a). Outline
(b). magnetic flux distribution
Fig.1 Conventional Rotor Structure of Inset PMSM
(a). Outline
(b)Magnetic flux distribution
Fig. 2 Geometrical Cross Section of Inset- Mounted Magnet PMSM Proposed
Fig.3 Flux density in air gap of conventional machine
Fig.4 Flux density in air gap of axial channel machine
Table 1. Machine Parameter
PMSM Parameter Symbols
Rotor Diameter
Magnet Height
Magnet Length
(up)
Magnet Length
(down)
Pole arch
Rotor teeth arch
axial hollow length
air gap length
Shaft diameter
Rotor of Inset Mounted Magnet
PMSM
Machine A
Conventional
Machine B
holes (under magnet
pole )
Rd
hm
lm1
0.11622
0.00630
0.02553
0.11622
0.00630
0.02553
lm2
0.02249
0.02249
Ɵp
Ɵrt
lh
g
sd
250
50
0.0021
0.030900
2
250
50
0.0760525
0.0021
0.0309002
Table 2. Simulation Result
No.
Name of Parameters
Conventional
Rotor
0.00209674
0.770626
-8.06922
Axial channel Rotor
1
2
3
4
5
Normal flux - W
Average B.n - T
MMF drop along
contour
A-t
Average H.t- A/m
Contour length - meters
-225.395
0.0358003–
159.231
0.0358003
6
Surface Area - meter^2
0.00272083
0.00272083
7
Force in x-direction - N
-237.353 N
-237.577 N
8
Force in y-direction- N
215.923 N
215.023 N
9
Torque about (0,0)- N*m 0.763123 N*m
0.80768 N*m
10
Average (B.n)^2
0.614552 Tesla^2
0.614778 Tesla^2
0.00209599
0.770351
5.70052
Table 3. Simulation Result ( continue )
Name of parameter
Conventional Rotor Axial channel rotor
core
core
Magnetic Field energy
- (J)
0.661469
0.662173
Magnetic Field co-energy
- (J)
4.668660
4.667020
0.008368
0.005657 ( small)
Rotor block cross section area - m^2
Conclusion
• By static simulation using FEMM 4.2, we
can see that axial channel in rotor
structure can decrease a little bit the
magnetic flux density in the air gap. But,
in many cases it may be constant and
depends on the type of stator slot design.
However, it can be acceptable as long does
not reach the saturation of the rotor core.
• From the simulation we see that the torque
of axial channel rotor is a little bit higher
compared to the conventional rotor
structure.
• From the picture, we can see that the
presence of the axial channel in the rotor
core, may assist heat transfer and cooling
system of machine and reduce the wieght of
the rotor. It can and increase the output
efficiency of the machine.
• Also, the axial increases the rotor mass is
tend to decrease and improved power – mass
ration and result lower moment of inertia (
higher mechanical time constant )
•
•
•
•
•
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Thank You