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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 3 (14)
ISSN 1843-6188
EXPERIMENTAL RESEARCH OF HARMONIC REGIME IMPACT
ON VIBRATION LEVEL OF ASYNCHRONOUS MACHINE
Ioan FELEA, Nicolae RANCOV
University of Oradea, Romania
E-mail: [email protected]
powering the motor with a six pulse inverter. Also, it
was take into account the power losses on magnetic core,
for a more precise estimation of machine parameters.
Some simple methods to estimate power losses in
magnetic core of ASM have been proposed [12, 13] and
also some models to determine power losses in magnetic
core have been developed and studied [14]. The models
take into account even the time variation of induction
motor parameters and take into consideration the skin
effect from rotor bars (squirrel-cage motor) when the
motor is powered through a converter. Also, a set of
correctional coefficients (saturation coefficient for
inductance of dispersion field, factor who establish if the
bar is high or not) have been introduced [15] to get an
equivalent circuit valid on steady state regime and also
in transitional regime.
To determine the equivalent circuit parameters of
motor it can be used finite element method [14]. This
analysis it’s based on parameters variation with
frequency and taking into account the saturation of
magnetic core and it gave good results in the case of a
response for fundamental frequency in the situation of
powering the motor with a inverter PWM [16, 17, 18].
The above mentioned analysis doesn’t take into
account the low-order harmonics, from the voltage
curve, in the case of powering the motor through an
inverter with sic pulses or in the case of magnetic core
saturation of power transformer. In [19] it’s proposed
an equivalent circuit (a new structure) of ASM, which
allows to study the behavior of ASM and to highlight
the effect or low-order harmonics from supply voltage
curve. A convenient change of parameters for the
equivalent circuit associated with the main magnetic
flux is done so the interaction between the saturation
effect of main magnetic flux and power losses from
magnetic core of dispersion magnetic flux it’s been
taken into account.
Determination method of ASM performances are,
currently, standardized through international standards
[20, 21]. It has been elaborated, also, rules for harmonics
regime measurements and to record power energy (PE)
parameters [22, 23].
Operation of ASM causes noise and vibration. The
producing mechanisms of these effects, in sinusoidal
regime of voltage and current are, mostly, well known
[24, 25, 26].
Abstract: The paper treats a very topical subject which fits
perfectly in field of investigation of the power energy quality
impact on operational performances of power systems.
Focused on the research field above mentioned, the paper is
structured in four parts. In the first part the effects of
harmonic regime (HR) of voltage and/or electrical current
on asynchronous machine (ASM) performances are
reviewed, ASM being seen as an essential component of
power systems.
In the second part the experimental research working method to
investigate the impact of HR on vibration level of ASM is
presented. The structure of experimental bench used and the
characteristics of the three regimes (supply voltages of ASM) are
given. In the third part of the paper the results are presented.
These are materialized through vibration characterization
elements such as: harmonic spectrum, vibrations amplitude and
the shifting of ASM shaft. The measurements were made in two
points of ASM and on three axes: vertical, horizontal and axial.
In the last part of the paper the conclusions of the conducted
research are synthesized.
Keywords: asynchronous machine, harmonic regime, vibrations
parameters, indicators
1. INTRODUCTION
Asynchronous machine (ASM) is the most typical power
energy consumer and therefore have a major impact on
power energy processes quality and efficiency. Field
literature [1÷10] mentions the negative effects of ASM
operation in current and voltage harmonic regime (HR):
 The increase of windings and magnetic core
temperatures;
 Electromagnetic torque changes which leads to the
reduction of ASM efficiency;
 The appearance of some oscillations of torsion torque
at the shaft of electrical machine;
 Changes of magnetic inductions in ASM air gap, due
to high-order harmonics;
 Interactions between the fundamental harmonic
magnetic flux and high-order harmonics magnetic flux.
It have been developed many methods and models[11,
12, 13] for studying ASM operating in harmonic regime,
which targets, mainly, electrically and energetically
effects. So an equivalent circuit of ASM has been
proposed, taking into considerations frequency
dependant parameters of machine for optimize the
efficiency of the motor, in the particular case of
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 3 (14)
ISSN 1843-6188
Experimental lab stand it’s composed by:
 Asynchronous Motor - DC Generator group also
named GR. M-G in figure 2;
 Harmonic regime generator (HRG) formed from a
alternative voltage variator, where we can adjust,
manually(through potentiometer), the firing angle of
thyristors (PP stands for “prescribed parameters”);
 Voltage rise autotransformer (AT) to hold the voltage
effective value between normal limits, voltage used to
supply the ASM;
 Vibration sensors for the three directions(vertical,
horizontal, axial) placed in measuring points;
 Power network analyzer(PNA) used to record the
parameters of PE used to supply ASM;
 Vibrations analyzer (VA) used to measure vibrations
parameters;
 Speed transducer (fv).
On figure 2 can be seen also excitation winding (Ex) and
loading rheostat of DCG (RL).
DC Generator (DCG) works at no-load. On figure 1 are
not seen HRG and AT, and the sensors (S1, S2) are
mounted on measurement point P2. (S3) sensor is
maintained on the same position (P1), axial vibration
being considered independent from the measurement
position.
The vibrations measurement has been done accordingly
with standard [30]. Measurement instruments (PNA,
VA) are approved and in metrological warranty period.
Used ASM is a three-phase asynchronous motor which
have the following characteristics:
- rated power Pr=4kW;
- connection schemes: Delta(∆)/Star(Y);
- rated voltages: Ur = 380 V/ 220 V;
- rated currents: Ir = 14,9 A/8,6 A;
- rated rotation speed: nr = 2840 rpm;
- rated frequency: f = 50 Hz;
- insulation class: E;
- protection degree(ingress protection) IP 54;
- mass m = 34 kg;
For the conducted analysis, ASM was supplied by three
different voltage regimes: sinusoidal (real), called also
reference regime (RR) – figure 3; harmonic regime no. 1
(RD1) – figure 4; harmonic regime no. 2 (RD2) – figure 5.
The three regimes were chosen so:
THDRR < THDRD1 < THDRD2
The present paper continues the previous works of the
authors [27, 28, 29, 31] towards of research the HR
effects on ASM performances throughout research of
HR impact on vibration level of ASM. The practical
results of this research, as presented in figures 6 ÷ 13,
comes to highlight the fact that the harmonic regime
tends to worse (as in increase) the vibration level of an
asynchronous motor which operates in HR.
2. WORKING PROCEDURE
For experimental research of HR impact on vibration
level of ASM it has been used lab stand highlighted in
figures 1 and 2.
Power network analzyer
Measurement point P2
Measurement point P1
Vibration analyzer
DC Generator(the load) Asynchronous motor ASM
Figure 1. Overview of experimental lab stand
3 × 400/ 230 V
50 Hz
R ,S ,T , O
VA
600.0
600.0
Measurement
points P1 , P2
AT
GR. M-G
ASM
HRG
fv
3~
DCG
=
400.0
400.0
Ex
+
-
RL
200.0
200.0
V0.000
0.000
PP
Ui
Ii
PNA
-200.0
-200.0
-400.0
-400.0
PC
-600.0
-600.0
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12:47:47.031
12:47:47.031
Figure 2. Electrical synoptic of used test bench
20.012
20.012 (mS)
(mS)
44 mSec/Div
mSec/Div
a) Supply voltage curve
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 3 (14)
ISSN 1843-6188
W aveform U1
409.58 Vrms, 4.39 %THD
600.0
600.0
100
90
80
400.0
400.0
70
60
50
200.0
200.0
40
30
V0.000
0.000
20
10
0
1
5
10
15
20
25
30
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35
40
45
-200.0
-200.0
50
b) Harmonic spectrum
-400.0
-400.0
Figure 3. –Features of RR
-600.0
-600.0
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12:20:20.793
12:20:20.793
600.0
600.0
1.000
1.000 (mS)
(mS)
200
200 uSec/Div
uSec/Div
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12:20:20.794
a) Supply voltage curve
400.0
400.0
W aveform U3
417.00 Vrms, 13.03 %THD
100
200.0
200.0
90
80
70
0.000
V0.000
60
50
40
-200.0
-200.0
30
20
10
-400.0
-400.0
0
1
-600.0
-600.0
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9/9/2009
12:13:26.337
12:13:26.337
20.012
20.012 (mS)
(mS)
44 mSec/Div
mSec/Div
5
10
15
20
25
30
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35
40
45
50
b) Harmonic spectrum
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12:13:26.357
Figure 5. – Features of RD2
a) Supply voltage curve
W aveform U3
387.26 Vrms, 6.80 %THD
3. MEASUREMENTS RESULTS
100
90
For the three supply voltages regimes of ASM (RR,
RD1, RD2), and with references to the two
measurements points and three measurements directions,
it has been recorded features for vibration level
parameters of ASM. As an exemplification in figure
6÷13 are given just parts of the measurements recorded.
Many more records can be found in [31].
80
70
60
50
40
30
20
10
0
1
5
10
15
20
25
30
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35
40
45
50
b) Harmonic spectrum
Figure 4. – Features of RD1
Figure 6. – Harmonic spectrum of vertical vibrations in RR, point P1
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 3 (14)
Figure 7. – Harmonic spectrum of vertical vibrations, in RD1, point P1
Figure 8. – Harmonic spectrum of vertical vibrations, in RD2, point P1
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 3 (14)
Figure 9. – Vertical vibrations amplitude in RR (P1, P2)
Figure 10. - Vertical vibrations amplitude in RD1 (P1, P2)
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 3 (14)
Figure 11. - Vertical vibrations amplitude in RD2 (P1, P2)
Figure 12. – Displacement of ASM shaft in cross-section plane, in RD1, point P1
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 3 (14)
ISSN 1843-6188
Figure 13. – The displacement of ASM shaft in cross-section plane, in RD2, in point P1
MEASUREMENTS SYNTHESIS
The measurements results were analyzed in three ways:
 Depending on harmonic spectrum;
As seen in the figures 6(reference regime), 7(harmonic
regime 1) and 8(harmonic regime 2) which represent the
harmonic spectrum of the vibrations on vertical direction,
in HR the amplitudes are higher for almost every
significant frequency (significant by its amplitudes)
mostly low order harmonics. We can observe though, for
high frequency harmonic orders the amplitudes tends to be
lower in HR than in RR but because the amplitudes are
very low these orders can be neglected. Also while in RR
some harmonics are missing or are very low (e.g. second
order harmonics, at 100 Hz) in HR they can be well
represented having important amplitude.
 Depending on vibration amplitudes (on vertical
direction);
As seen in the above figures 9(for RR), 10(for RD1) and
11(for RD2) representing the vertical vibrations for the
three mentioned regimes it’s clearly that HR have a
negative impact on ASM cause the vibrations are
significant higher than in reference regime(RR). In RR
we have obtained a mean value for the vertical vibrations
(figure 8) around 20 ÷ 30 mm/s while in HR we got
values around 70 ÷ 80 mm/s, which are a major increase
of vibration level. Also while HR is worsens, as shown in
figures 10 and 11, it’s obvious that the vertical vibrations
variations (around average value) are increasing.
 Depending on the displacement of the SM shaft.
As regarding to the displacement of ASM shaft which
is the movement of ASM shaft in a cross-section plane,
as presented in figures 12 and 13 it becomes even more
obvious the effect of HR on ASM vibration level,
meaning that while HR worsens (THD increases) the
displacement of ASM shaft increases also (vibrations
amplitudes composed on vertical and horizontal
direction in a cross-section plane) with direct action on
ball-bearings of ASM.
4. CONCLUSIONS
Identification of negative impact of HR on ASM
vibration level substantiates on the fact that, the
diagnosis through vibrations of machines, equipments
and installations operation state have as a support energy
transfer process, certain components may be mechanical
excited, causing them to vibrate.
For a full characterization of ASM vibration level it’s
necessary to measure the vibrations on all three axes:
vertical, horizontal and axial.
The increased amplitude of vibrations, caused by
operation in HR, leads to composition of horizontal and
vertical movement, on cross-section plane and so, the
increase of the displacement of ASM shaft in this plane.
This displacement has direct action on ball bearings or
bearings, respectively on ASM shaft.
Comparing vibration values of the two regimes RD1 and
RD2 against the values from RR we can assert with
certainty that, in HR, vibrations amplitude level on all
three directions; vertical, horizontal and axial are higher
than those on reference regime (RR).
Vibrations level increases significantly with the
worsening of HR, so over certain limits of it, vibrations
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 3 (14)
are beyond the limits given in standards. So ASM long
term operation in harmonic regime can lead to ASM
failure, especially the failure of mechanical sub-system
of ASM.
It is apparent a close relationship between vibrations
amplitude respectively ASM displacement of the shaft
and THD (total harmonic distortion) indicator of HR.
We have to emphasize that our analysis did not aimed to
establish an exact, numerical, correspondence between
vibrations level and the harmonic regime (THD more
precisely) on a ASM operating in HR, due to equipments
limitations (more exactly due to HRG instability at
different loads and the difficulty to maintain the effective
supply voltage ASM at the exact same rated value). For
definitive answers and analytical substantiations a
further research is required.
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