Industrial Electrical Engineering and Automation Lund University, Sweden L7: Magnetic circuits Magnetic cores are used to conduct the magnetic flux and permanent magnets to produce flux eien20vt18 Industrial Electrical Engineering and Automation Avo R Design of Electrical Machines 2 Previous lectures: Design Target mech T el P T dt t i t u T P 0 1 • Energy conversion • Torque per rotor volume • Air-gap shear stress • Product of magnetic and electric loadings B l r w z K T F 2 2 2 gap RT A F l r Fr V T BK A BKwz A BIz A F gap gap gap η - efficiency σ=kBK Industrial Electrical Engineering and Automation Avo R Design of Electrical Machines 3 Industrial Electrical Engineering and Automation Avo R Design of Electrical Machines 4 Today’s goal • Scope on permanent magnet machines • Soft and hard magnetic materials • Main flux path in a magnetic circuit • Dimensioning the size of the magnetic circuit for PMSM
11
Embed
Previous lectures: Design Target - iea.lth.se · RM @ Ansys RMxprt • Aligned and unaligned flux linkage Industrial Electrical Engineering and Automation Avo R Design of Electrical
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Industrial Electrical Engineering and AutomationLund University, Sweden
L7: Magnetic circuits
Magnetic cores are used to conduct the magnetic flux and permanent magnets to
produce flux
eien20vt18
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 2
Previous lectures: Design Target
mech
T
el PTdttituT
P 0
1• Energy conversion
• Torque per rotor volume
• Air-gap shear stress
• Product of magnetic and electric loadings
B
l
r
wz K
T
F
22
2 gapRT AF
lrFr
VT
BKA
BKwzABIz
AF
gapgapgap
η - efficiency
σ=kBK
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 3
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 4
Today’s goal
• Scope on permanent magnet machines• Soft and hard magnetic materials• Main flux path in a magnetic circuit• Dimensioning the size of the magnetic circuit for PMSM
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 5
Electric machine torque and components
• Coil or winding – to produce variablemagnetic flux
• Permanent magnet – to produce invariablemagnetic flux
• Soft magnetic core – to provide an easy path for the flux
• T=ψmisy+isxisy(Lx-Ly)
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 6
Electrical machine examples
• Electrical machines with stator magnetization
– Induction machine– Reluctance machine
• Presence of magnetic core and very small air-gap are essential
• Same size, voltage and power
– Ø155/94-H120 mm– 2.2kW, 400V, 50Hz
-B-B
-B+A
+A+A
-C-C-C+B+B+B-A
-A-A
+C+C+C-B-B
-B+A
+A+A
-C -C -C +B +B +B-A
-A-A
+C+C+C47.3 7715.0
+A
-C
+C-B
+B
-A
+A
-C
+C -B
+B
-A
47.3 7715.0
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 7
Induction machine
• Induction machine is an electrical transformer– the magnetizing circuit is seen from no load test (NLT)– leakage inductances are found from locked rotor test (LRT)
• Load resistance Rr’/s consists of equivalent electromechanical load resistance Rr’(1-s)/s and actual winding resistance Rr’
• Torque, current and efficiency @ 400V from 50 to 100Hz
Characteristics
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 16
Reluctance machine
0 20 40 60 80 100 120 140 160 180-25
-20
-15
-10
-5
0
5
10
15
20
25
torq
ue, T
[Nm
]
0 20 40 60 80 100 120 140 160 1800.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0.11
0.12
indu
ctan
ce, L
[H]
position, e [deg]
Torque and flux linkage at nominal current 6.5Apk and at the doubled current level
0 20 40 60 80 100 120 140 160 180-40
-30
-20
-10
0
10
20
30
40
torq
ue, T
[Nm
]
0 20 40 60 80 100 120 140 160 1800
0.05
0.1
0.15
0.2
0.25
indu
ctan
ce, L
[H]
position, e [deg]
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 17
RM @ Ansys RMxprt
• Aligned and unaligned flux linkage
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 18
RM Tω - characteristics
IT
P
η
Industrial Electrical Engineering and AutomationLund University, Sweden
Home assignment A3
Performance estimation for a three-phase PM synchronous machine
B
Hc
Do
B A
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 20
Magnetisation
• % magnetic dimensioning• mu0 = 4*pi*1e-7; % magnetic permeability in vacuum• K_C = 1.2; % Carter's coefficient• Bgm = 0.8; % maximum flux density in the air-gap• mu_pm = 1.219; % permeability of permanent magnet• Br = 1.1; % remanence flux ensity of permanent magnet• K_m=2/3; % relative width of magnet• % fundamental space component of gap magnet flux density• Bgm1=4/pi*Bgm*sin(K_m*pi/2);
000
C
gpm
pm
rpm kgB
hBB
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 21
Multi-phase winding distribution
• Multi-phase constant balanced instantaneous power• A sinusoidal generated voltage is desirable • A sinusoidal variation of flux density round the rotor• Magnetic cores, distributed and concentrated windings In
dust
rial E
lect
rical
Eng
inee
ring
and
Aut
omat
ion
Avo R Design of Electrical Machines 22
Magnetic coupling
E=ΨmωΨmI=T
Indu
stria
l Ele
ctric
al E
ngin
eerin
g an
d A
utom
atio
n
Avo R Design of Electrical Machines 23
Main flux path
• A linear characteristicscan be assumed in materials
• μpm=1, μfe=∞,• The hysteresis and eddy
currents are neglected, if the study does not require them explicitly.
• The geometry is simplified by excluding small radii, holes etc