Additional no-load losses in inverter-fed high-speed cage induction motors |
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Authors: | Email author" target="_blank">G?Joksimovi?Email author A?Binder |
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Affiliation: | (1) Department of Electrical Energy Conversion, Darmstadt University of Technology, Landgraf-Georg-Strasse 4, 64283 Darmstadt, Germany |
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Abstract: | An analysis of additional high-frequency losses in high-speed cage induction motors with closed rotor slots under sinusoidal and inverter supply at no load is presented. Calculated losses are compared with experimental results obtained by measurement on a 270 kW, 16,200/min, prototype motor, at both the delta and star connections of the stator winding. The main additional losses of the prototype motor investigated due to inverter supply are eddy current losses in the stator winding. Both measurement and calculation show that, at the delta connection, the additional losses are higher due to the lower modulation degree of the inverter, causing higher harmonic voltage amplitudes.List of symbols
B
magnetic flux density, T
-
b
sheet
width of iron sheet, m
-
b
bar
mean width of rotor bar, m
-
b
sd
mean stator tooth width, m
-
b
Qm
mean slot width, m
-
b
LT
square wire side, m
-
f
frequency, Hz
-
h
bar
rotor bar height, m
-
h
br
rotor slot bridge height, m
-
h
sy
stator yoke height, m
-
I
current (rms value), A
-
k
ordinal number of voltage harmonic
-
k
C
Carter s factor
-
k
dHy
hysteresis deterioration factor for teeth
-
k
dFt
eddy-current deterioration factor for teeth
-
k
Fe
iron stack fill factor
-
K
l1k
first-order skin effect coefficient of stator inductance for kth voltage harmonic
-
K
l2k
second-order skin effect coefficient of stator inductance for kth voltage harmonic
-
K
1k
first-order skin effect coefficient of stator resistance for kth voltage harmonic
-
2k
second-order skin effect coefficient of stator resistance for kth voltage harmonic
-
k
yHy
hysteresis deterioration factor for yoke
-
k
yFt
eddy-current deterioration factor for yoke
-
k
w1
winding factor for fundamental space harmonic
-
l
b
length of winding overhang, m
-
l
Fe
core length, m
-
L
dc
inductance at d.c. current, H
-
L
r
rotor inductance, H
-
L
s
stator inductance, H
-
M
torque, Nm
-
m
T
number of vertically arranged coils in slot
-
m
TZ
number of vertically arranged conductors in slot
-
n
N
rated speed, 1/min
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p
number of pole pairs
-
p
Ft
eddy current losses per iron mass at 50 Hz, 1 T, W/kg
-
p
Hy
hysteresis losses per iron mass at 50 Hz, 1 T, W/kg
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P
Cu
copper losses, W
-
P
Fe
iron losses, W
-
P
Fe,Hy
hysteresis losses, W
-
P
Fe,Ft
eddy-current iron losses, W
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P
fr
friction and windage losses, W
-
Q
r
number of rotor slots
-
Q
s
number of stator slots
-
R
s
stator phase resistance,
-
R
r
rotor phase resistance,
-
R
dc
resistance at d.c. current,
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s
slip
-
s
k
slip for kth harmonic
-
U
voltage (rms value), V
-
V
volume, m3
-
N
number of turns per phase
-
z
1
average number of conductors in one turn, lying side by side
-
z
2
average number of vertically arranged conductors per turn
-
air-gap length, m
-
magnetic flux, Wb
-
electric conductivity, S/m
-
permeability (
0=4 ×10–7 H/m: permeability of vacuum), H/m
-
r
relative permeability
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Fe
mass density, kg/m3
-
s
leakage coefficient for stator winding
-
p
pole pitch, m
-
sd
stator tooth pitch, m
G. Joksimovi is on research leave from University of Montenegro, Montenegro, Yugoslavia |
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Keywords: | Induction motors Additional losses Inverter supply High speed |
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