Joint Detection of Stator Winding Inter-turn
Short Circuit and Rotor Bar Breaking Fault in
Squirrel Cage Induction Motors
XU Bo-qiang, LI He-ming, SUN Li-ling
Absfract-The s t a t o r winding inter-turn short a n d rotor bar
breaking a r e both frequent fault in squirrel cage induction motors.
T h e previous w o r k is inclined to detect one single fault, in other
words, to detect the s t a t o r winding inter-turn short circuit o r
rotor b a r breaking fault, separately. Hence there exists the
misdetection probability due to the inter-influence of them. To
solve t h a t problem, this paper addresses to the joint detection of
the two faults. Firstly, this paper completes the numerical
simulation by utilizing the multi-loop mathematical model.
Secondly, some creative a n d interesting conclusions, which depict
explicitly the inter-influence of the s t a t o r winding inter-turn short
a n d rotor b a r breaking fault, have been d r a w n based on the
thorough analysis of the simulation results. Finally, a series of
tests verify the necessity a n d effectiveness of the joint detection,
which reduces t h e misdetection probability to a great extent. T h e
further w o r k will focus on refining the joint detection and
applying it to t h e industrial site.
Index Terms-Detection,
fault diagnosis, induction motors,
insulation failure, rotor fault, squirrel cage motors, stator
winding fault.
proposed [9-1'1, based on the principle that when rotor bar
breaking fault occurs, a superimposed current component will
be induced in the stator at the frequency of (1 - 2 S ) f s , where
S is the per unit slip and f, is the supply frequency ["I.
Obviously, the previous work is inclined to detect one single
fault, in other words, to detect the stator winding inter-turn
short circuit or rotor bar breaking fault, separately. Unlike with
that, this paper focuses on the joint detection of the two faults
in squirrel cage induction motors.
The paper is organized as follows. Section I1 introduces the
multi-loop mathematical model of squirrel cage induction
motors, which is suitable for the joint simulation of the stator
winding inter-turn short circuit and rotor bar breaking fault. In
Section 111, quite a few creative and interesting conclusions
have been drawn, based on the thorough analysis of the
relevant simulation results. Section IV demonstrates the test
rig briefly and provides the experimental results to validate the
joint detection of the stator winding inter-turn short circuit and
rotor bar breaking fault.
11. MULTI-LOOP MODEL
I. INTRODUCTION
I
NDUCTION motors possess a very important role in a wide
variety of industrial applications. From a number of surveys
11-51, it can be deduced that, for induction motors, the stator
winding related failures account for approximately 30% of all
failures, the majority of which result from the breakdown of
the turn-to-turn insulation. Moreover, these surveys point out
that the rotor bar breaking also occurs frequently with the
probability about 10%. Therefore, early detection of the stator
winding inter-turn short circuit and rotor bar breaking fault in
squirrel cage induction motors would help avoid catastrophic
failures, reduce repair cost and outage time.
The subject to detect stator winding inter-turn short circuit
fault has been addressed by some researchers [6-81. The
technique, based on the measurement of the stator negative
sequence current, is the most practical and successful [81. At the
same time, a number of approaches to detect rotor bar
breaking fault in squirrel cage induction motors have been
Xu Bo-qiang is with North China Electric Power University, P. 0 Box 20
071003 Bao Ding China (e-mail: xbqsllxtz@163.net).
Li He-ming is with North China Electric Power University, I? 0. Box 20
071003 Bao Ding China (e-mail. lihernin:j7(~263,net).
Sun Li-ling is with North China Electric Power University, P. 0. Box 20
071003 Bao Ding China (e-mail: sllutz@sina.com).
0-7803-7459-2/02/$17.00 Q 2002 IEEE
The multi-loop model for the general induction motors with
m stator circuits and n rotor bars can be written in vectormatrix form as follows ['3,7,'4,151:
where [Us] is the stator voltage m x 1 matrix, [U,] is the rotor
voltage n x 1 matrix, [ I s ] is the stator current m x l matrix,
[f,] is the rotor current n x 1 matrix, [Ys] is the stator flux
linkage m x l matrix, [W,] is the rotor flux linkage n x l
matrix, [R,] is the stator resistance m x m matrix, [R,] is the
rotor resistance n x n matrix, [ L s s ] ,[Lrr], [L,,] and [L,] are
m x m , n x n , m x n and n x m inductance matrix
respectively.
The equations describing the mechanical part of the system
are:
-761
-
.
where Te is the electromagnetic torque, R I is the angular.
mechanical synchronous speed, wr is the angular mechanical
speed, T, is the load torque, J is the combined inertia.
It is worthy mentioning that the numbers of the stator and
rotor loop, the resistances, and the inductances should be
adjusted appropriately, to simulate stator winding inter-turn
short circuit and rotor bar breaking fault, detailed in [7, 14,151.
Tune (I)
Turn (a)
(d) Stator negative sequence current
(c) Stator c-phase current
1
111. SIMULATION RESULT ANALYSIS
A series of numerical simulation for a 3 kW squirrel cage
induction motor is completed according to the multi-loop
model in Section 11. Here cites the typical simulation results.
The simulation result under the condition that the motor is
healthy is shown in Fig. 1 .
1 J ' d
L m - A
Frvocncy (Hz)
G5
(e) Stator a-phase FFT spectrum
Fig 2 Simulation result under the condition that the inter-turn short circuit
occurs singly
The simulation result under the condition that the rotor bar
breaking occurs singly is shown in Fig. 3.
I ,10,
I
#
Tune (a)
(a) Stator a-phase current
(b) Stator b-phase current
Tune 1s)
(c) Stator c-phase current
(d) Stator negative sequence current
,
-
!
(c) Stator c-phase current
(d) Stator negative sequence current
I
--, x
!!UM
Id:
VI
The simulation result under the condition that the inter-turn
short circuit occurs singly is shown in Fig. 2.
Fiequamy (Hzl
(e) Stator a-phase FFT spectrum
Fig 3 Simulation result under the condition that the rotor bar breaking
occurs singly
Table 1 indicates the phase gaps of the stator current under
those three conditions.
TABLE 1
PHASEGAPS OF THE STATOR CURRENT
Motor State
Healthy
Inter-turn
Short Circuit
Rotor Bar
Breaking
Tunc 1,)
(b) Stator b-phase current
-
762 -
I
I
a, b phase
118.8"
95.4"
118.8"
1
I
a, c phase
-118.8"
-142.2"
-119.7"
1
I
b, c phase
118.8"
120.6"
119.7"
Based on th& quite a few creative and interesting
conclusions have been drawn, listed below.
Stator winding inter-turn short circuit fault, serious to a
certain extent, will lead to the (1 - 2S)fs component
emerges in the stator current, just like rotor bar breaking
fault, due in part to the bilateral electromagnetic induced
relationship in induction motors. It implies that the rotor
bar breaking detection approaches, presented in [9-111,
will possibly interpret stator winding inter-turn short
circuit fault as rotor bar breaking fault, incorrectly.
Rotor bar breaking- fault, serious to a certain extent, will
lead to the negative sequence component emerges in the
stator current, just like stator winding inter-turn short
circuit fault. It indicates that the stator winding inter-turn
short circuit detection approach, presented in [SI, will
possibly regard rotor bar breaking fault as stator winding
inter-turn short circuit fault, incorrectly.
Stator winding inter-turn short circuit fault will cause the
phase unbalance of the stator three-phase current.
Whereas, the stator three-phase current still remains
symmetry in the phase, and in the amplitude, under rotor
bar breaking fault. As allows stator winding inter-turn
short circuit and rotor bar breaking fault to be
distinguished.
Stator winding inter-turn short circuit fault will give rise
to the odd harmonics component in the stator current,
differently with rotor bar breaking fault. As also allows
these two faults to be distinguished, although the odd
harmonics component is rather faint.
The stator winding inter-turn short circuit detection
approach presented in [SI, and the rotor bar breaking
detection approaches presented in [9-111, still can be
utilized as the basic methods. Note that the phase balance
or unbalance of the stator three-phase current must be
taken into consideration to improve the detection
reliability.
sampling interval is 0.1 ms , i.e., 1.8" (the power supply
frequency
.
. is 50 Hz >.
I
-- n r w - b r
Tnne ( s i
01
"3
Tme (s)
0'2
04
(b) Stator b-phase current
(a) Stator a-phase current
I
8,
(d) Stator negatlve sequence current
(c) Stator c-phase current
.
-6r
,
,
(e) Stator a-phase FFT spectrum
Fig. 4 Experimental result under the condition that the inter-turn short circuit
occurs singly
IO,
.
IO,
IV. LABORATORY TEST
The test motor used in the experimental investigation is a
three-phase, 50 Hz , 2-pole, 3 kW , squirrel cage induction
motor, type YlOOL-2, rated at 380 V , 6.1 A , and 2880 rpm .
The stator winding has been modified by addition of a number
of taps connected to the stator coils, for each of the three
phases, allowing for the introduction of shorted turns at several
locations in the stator winding. At the same time, some extra
rotors, healthy or with broken bar(s), are provided in order to
model the rotor bar breaking fault.
Initially, shorted turns were introduced in the stator a-phase
winding while the rotor was normal. Subsequently, a faulty
rotor substituted for the normal one while the shorted turns
were removed. The corresponding results are given in Fig. 4,
Fig. 5, respectively. And the phase gaps of the stator current
are given in Table 11. The stator three-phase currents were
sampled by using a high-frequency multi-channel data
acquisition device, type WS-P603 16/C, and delivered to
MATLAB6.1 for thorough processing and analysis. The
4
n:
n1
.
&
U
(a) Stator a-phase current
1 0 , .
- 763 -
,
,
.
.
,
,
I
(b) Stator b-phase current
3"
4
y
-
j
(d) Stator negative sequence current
7
% I
40
no
iio
Frequency (Hz)
IF*,
zn
( e )Stator a-phase FFT spectrum
Fig. 5 Experimental result under the condition that the rotor bar breaking
occurs singly
TABLE I1
PHASEGAPSOF THE STATOR CURRENT
G. B. Kliman, W. J. Premerlani, R. A. Koegl, D. Hoeweler, “Sensitive,
on-line turn-to-turn fault detection in AC motors,” Electric Machines
and Power Systems, vol. 28, pp. 915-927, 2000.
G. B. Kilman, J Stein, R. D. Endicott, M. W. Madden, “Noninvasive
detection of broken rotor bars in operating induction motors,” IEEE
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1988.
JIANG Jian-guo. WANG Qing-sheng, YANG Bing-shou, QIU A-rui,
“Applying the adaptive noise cancellation to extract the features of
squirrel cage induction motor with rotor defects,” Transactions of
China Electrotechnical Society, No. 4, pp. 176-179, November 1996.
Qiu A-rui, “New approach of extracting rotor fault feature in induction
motors,” Journal of Tsinghua University (Sci & Tech), vol. 37, No. I ,
pp. 35-37, January 1997.
W. Deleroi, “Broken bar in squirrel cage rotor of an induction motor,
Part 1: Description by superimposed fault currents,’’ Arch. fur
Elektrotechnik, pp 91-99, 1984.
X. Luo, Y. Liao, H.A. Toliyat, A. El-antalby, T.A. Lipo, “Multiple
coupled circuit modeling of induction machines,” IEEE Trans. on
Industry Applications, vol. 31, No. 2, pp. 31 1-317, March-April 1995.
V. Devanneaux, H. Kabbaj, B. Dagues, J. Faucher, “An accurate model
of squirrel cage induction machines under rotor faults,” in Proc. 2001
Electric Machines and Systems International Conf., pp. 384-387.
QIU A m i , ZHANG Long-zhao, “Steady-state operation analysis of the
squirrel-cage induction motors with rotor-bar and end-ring faults,”
Transactions of China Electrotechnical Society, No. 4, pp. 7-12,
August 1996.
Breaking
Apparently, the above experimental results validate the
conclusions presented in Section 111, as well as verify the
necessity and effectiveness of the joint detection of the stator
winding inter-turn short circuit and rotor bar breaking fault in
squirrel cage induction motors.
V. CONCLUSION
The stator winding inter-turn short and rotor bar breaking
are both frequent fault in squirrel cage induction motors.
Previous researchers paid their attention to the detection of one
single fault, ignoring the inter-influence of the two faults. This
paper concentrates on the joint detection of the stator winding
inter-turn short and rotor bar breaking fault. Firstly, this paper
has completed the numerical simulation by utilizing the multiloop mathematical model. Secondly, quite a few creative and
interesting conclusions, which depict explicitly the interinfluence of the two faults, have been drawn based on the
thorough analysis of the simulation results. Finally, a series of
tests verify the necessity and effectiveness of the joint
detection, which reduces the inisdetection probability to a
great extent. The hrther work will focus on refining the joint
detection and applying it to the industrial site.
VI. REFERENCES
IAS Motor Re!iability Working Group, “Report of large motor
reliability survey of industrial and commercial installations, Part I,”
IEEE Trans. on Industry Applications, vol. 21, No 4, pp. 853-864,
July-August 1985.
IAS Motor Reliability Working Group, “Report of large motor
reliability survey of industrial and commercial installations, Part 11,”
IEEE Trans. on Industry Applications, vol 21, No. 4. pp. 865-872,
July-August 1985.
IAS Motor Reliability Working Group, “Report of large motor
reliability survey of industrial and commercial installations, Part 111,”
IEEE Trans. on Industry Applications, vol 23, No. I , pp. 153-158,
January-February 1987.
P. F. Albrecht, J. C. Apiarius, D. K Shanna, “Assessment of the
reliability of motors in utility applications,” IEEE Trans. on Energy
Conversion, vol. 2, No. 3, pp. 396-406, September 1987.
Olav Vaag Thorsen, Magnus Dalva, “A survey of faults on induction
motors in offshore oil industry, petrochemical industry, gas terminals,
and oil refineries.” IEEE Trans. on Industry Applications, vol. 31, No.
5, pp. 1186-1196, September-October 1995.
J. Penman, H. G. Sedding, B A Lloyd, W. T Fink, “Detection and
location of inter-turn short circuits in the stator windings of operating
motors,” IEEE Trans. on Energy Conversion, vol. 9, No. 4, pp. 652658, December 1994.
Gojko Joksimovk, Jim Penman, “The detection of inter-turn short
circuits in the stator windings of operating motors,” in Proc. 1998
IEEE Industrial Electronics Society Conf., pp. 1974-1979.
VII. BIOGRAPHIES
Xu Bo-qiang was born in Xiong County, He
Bei Province, China, on April 9, 1972 He
received the B D and M D both from North
China Electric Power University in 1994 and
1997, respectively
He has been with North China Electric Power
University from 1997, where he is currently a
lecturer in Electric Power Engineering
Department. His teaching interests cover electric
machines and power electronics. He is interested in the condition monitoring
and fault diagnostics of electric machines and working towards the Ph. D
degree of that. He has published more than I O papers in technical journals.
Li He-ming was born in Yi County, He Bei
Province, China, on September 9, 1957. He
received the B. D. from North China Electric
Power University in 1982 and M. D. from Zhe
Jiang University in 1987.
He has been with North China Electric Power
University from 1982, where he is currently a
professor in Electric Power Engineering
Department, vice president of the university
His major research interest lies in the area of
electric machine desien. monitorine and
diagnosis He has published more than 50
papers in technical journals conference proceedings
- 764 -
Y
Sun Li-ling was born in Zhao County, He Bel
Province, China, on December 15, 1972 She
received t k B D from He Bei Electromechanical Institute in 1994 and M D from
North China Electric Power University in 1997
She has been with North China Electric
Power University from 1997, where she is
currently a lecturer in Electric Power
Engineering Department Her research area is ,
the condition monitoring and fault diagnosis of
electric machines She has published more than
I O papers in technical journals