Tài liệu High Frequency Lumped Parameter Model for AC Motor Windings
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+,*+ )5(48(1&< /803(' 3$5$0(7(5 02'(/ )25 $& 02725 :,1',1*6 G. Grandi *, D. Casadei *, A. Massarini ** * Dept. of Electrical Engineering, viale Risorgimento 2 , 40136, Bologna  Italy ** Dept. of Engineering Sciences, via Campi, 203/B, 41100, Modena  Italy Abstract. The paper describes a HF equivalent circuit for the stator winding of threephase AC motors, valid in a wide frequency range. The model fitting is based on winding complex impedance measurements. Both the phasetophase and the phasetoground impedances are considered. The proposed model can be utilized in theoretical and numerical HF analysis of inverterfed AC motors. In this case, the equivalent circuit allows to predict both differential and commonmode conducted EMI. Furthermore, also transient effects can be predicted when the analysis is performed in the time domain. The numerical results, obtained by means of PSpice, are compared with the corresponding experimental tests in both frequency and time domains. Keywords. HF model, equivalent circuit, AC winding, conducted EMI ,1752'8&7,21 6,1*/( &2,/ 02'(/ In recent years, inverter motor drives have become the most popular systems to handle electromechanical power conversion. The modern power converters are based on switching mode operation with static components of the last generation. The static switches, such as MOSFETs and IGBTs, are characterized by very fast commutations (i.e., fractions of µs). The switching frequency is usually fixed in the range of tens of KHz to avoid acoustic noise. As a consequence, undesired harmonic voltage components can range from tens of KHz to several MHz. These High Frequency (HF) voltage harmonics are responsible of HF currents. The propagation path of the current harmonics is rather unexpected owing to stray and parasitic motor parameters that take importance at high frequency. Thus, a circuit model of the motor windings is particularly useful to predict HF current components and, in general, conducted ElectroMagnetic Interferences (EMI) [1]. Since the motor frame is usually grounded, both differential and commonmode EMI must be considered. In the low and medium power range, the low voltage induction motor is the most frequently used type of motor. The windings of this type of motor are usually realized by a series connection of mush wound coils. A winding model consisting in a cascade connection of singlecoil models can be particularly useful to determine the fast fronted voltage distribution a...
+,*+)5(48(1&</803('3$5$0(7(502'(/)25$&02725:,1',1*6
G. Grandi
*
, D. Casadei
*
, A. Massarini
**
*
Dept. of Electrical Engineering, viale Risorgimento 2 , 40136, Bologna  Italy
**
Dept. of Engineering Sciences, via Campi, 203/B, 41100, Modena  Italy
Abstract. The paper describes a HF equivalent circuit for the stator winding of threephase AC
motors, valid in a wide frequency range. The model fitting is based on winding complex im
pedance measurements. Both the phasetophase and the phasetoground impedances are con
sidered. The proposed model can be utilized in theoretical and numerical HF analysis of in
verterfed AC motors. In this case, the equivalent circuit allows to predict both differential and
commonmode conducted EMI. Furthermore, also transient effects can be predicted when the
analysis is performed in the time domain. The numerical results, obtained by means of PSpice,
are compared with the corresponding experimental tests in both frequency and time domains.
Keywords. HF model, equivalent circuit, AC winding, conducted EMI
,1752'8&7,21
In recent years, inverter motor drives have become the
most popular systems to handle electromechanical
power conversion. The modern power converters are
based on switching mode operation with static compo
nents of the last generation. The static switches, such as
MOSFETs and IGBTs, are characterized by very fast
commutations (i.e., fractions of µs). The switching fre
quency is usually fixed in the range of tens of KHz to
avoid acoustic noise. As a consequence, undesired har
monic voltage components can range from tens of KHz
to several MHz. These High Frequency (HF) voltage
harmonics are responsible of HF currents. The propaga
tion path of the current harmonics is rather unexpected
owing to stray and parasitic motor parameters that take
importance at high frequency. Thus, a circuit model of
the motor windings is particularly useful to predict HF
current components and, in general, conducted Electro
Magnetic Interferences (EMI) [1]. Since the motor
frame is usually grounded, both differential and com
monmode EMI must be considered.
In the low and medium power range, the low voltage in
duction motor is the most frequently used type of motor.
The windings of this type of motor are usually realized
by a series connection of mush wound coils. A winding
model consisting in a cascade connection of singlecoil
models can be particularly useful to determine the fast
fronted voltage distribution among the coils [2][6].
Owing to the random distribution of the turns in each
coil, an analytical evaluation of the coil model cannot be
based on singleturn models such as in form wound
coils. Hence, the lumped equivalent circuit of a coil can
be defined in terms of equivalent impedance by a proper
threeterminal circuit. Both the real and imaginary com
ponents of the impedance [7] or only the impedance
magnitude [8] can be considered. In this paper the main
results obtained in [7] are summarized and extended to
the case of multicoil stator windings with reference to
threephase induction motors.
6,1*/(&2,/02'(/
A detailed analysis of singlecoil stator windings has
been presented in [7] leading to the lumped parameter
model represented in Fig. 1.
C
1
L
1
R
C1
R
L1
R
P1
C
2
L
2
R
C2
R
L2
R
P2
iron (ground)
C
g
R
g
R
g
C
g
Fig. 1: HF equivalent circuit of a mush wound coil
The coil is regarded as a series connection of N turns
having a circular cross section. The distribution of the N
turns is random in both the slot region and the overhang
region. The coil geometry and the coil cross section in
the slot region are given in Fig. A1 of the Appendix.
%DFNJURXQG
The HF circuit model of a mush wound coil proposed in
[7] considers both turntoturn and turntoiron capaci
tances. Also additional dissipative phenomena such as
skin and proximity effects in the wires, dielectric and
iron losses are taken into account. The proposed ap
proach is based on the equivalence between the coil and
the circuit model in terms of complex impedance =
c
.
Hence, both the real part (equivalent series resistance)
and the imaginary part (equivalent series reactance) of
=
c
are considered.
Experimental tests on several coils have been carried
out, showing in all cases a pair of more or less smoothed
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Tài liệu High Frequency Lumped Parameter Model for AC Motor Windings

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Tài liệu High Frequency Lumped Parameter Model for AC Motor Windings
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