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IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 54, NO. 3, JUNE 2007
Practical Rules for Assessment of Inverter-Induced
Bearing Currents in Inverter-Fed
AC Motors up to 500 kW
Annette Muetze, Member, IEEE, and Andreas Binder, Senior Member, IEEE
Abstract—The influence of different parameters of a variablespeed drive system on the phenomena of inverter-induced bearing
currents has been studied under exactly the same conditions on
inverter-operated alternating current motors from 1 to 500 kW.
Detailed modeling may not always be applicable with practical
applications in the field, where many parameters might be unknown. Therefore, the most important correlations are summarized in the form of a flowchart that is based on the physical
cause-and-effect chains. This flowchart can serve as a tool for
engineers to estimate the endangerment of a drive system due
to inverter-induced bearing currents and select an appropriate
mitigation technique if necessary, where detailed knowledge of the
different design parameters is not available.
Index Terms—Bearings (mechanical), failure analysis, fault
diagnosis, variable-speed drives.
I. I NTRODUCTION
T
HE PHENOMENA of additional bearing currents in speed
drive systems due to fast switching insulated gate bipolar
transistor inverters have been reported for almost a decade
(e.g., [1]–[21]). So far, research has focused on the physical
explanation for a given drive system on a particular power
level. Therefore, a thorough analysis of the qualitative and
quantitative significance of the different parameters on the
bearing current phenomena was carried out on motors from
less than 1 up to 500 kW and is presented. The investigation
was done under identical conditions for all investigated drive
configurations rendering direct comparison of the obtained
results possible [22]. With respect to the present still incomplete
understanding of the endangerment of the bearing, areas of safe
operation can be identified and a drive setup can be chosen as
simple as necessary to protect the bearing without paying the
cost for unnecessary devices.
Manuscript received February 21, 2005; revised July 29, 2005.
A. Muetze was with the Institute of Electrical Energy Conversion, Darmstadt
University of Technology, 64283 Darmstadt, Germany. She is now with the
School of Engineering, University of Warwick, Coventry, CV4 7AL, U.K.
(e-mail: A.Muetze@warwick.ac.uk).
A. Binder is with the Institute of Electrical Energy Conversion, Darmstadt
University of Technology, 64283 Darmstadt, Germany (e-mail: abinder@ew.
tu-darmstadt.de).
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TIE.2007.894698
Fig. 1.
Cause-and-effect chains of inverter-induced bearing currents.
II. R EVIEW OF B EARING C URRENTS IN
I NVERTER -F ED M OTORS
A voltage-source inverter presents a common mode voltage
source. The high-frequency (HF) components of the common
mode voltage interact with capacitances of the motor that are
not of influence at line operation, thereby possibly generating inverter-induced bearing currents. Four types of inverterinduced bearing currents can be distinguished (Fig. 1). The first
two are related to the influence of the common mode voltage
vcom on the bearing voltage vb ; the last two are caused by
ground currents ig that result from the interaction of vcom with
high dv/dt and the capacitance between stator winding and
motor frame Cwf .
1) At low bearing temperature (Tb ≈ 25 ◦ C) and motor
speed n ≥ 100 r/min, the dv/dt over the bearing, along
with the bearing capacitance Cb , causes small capacitive
bearing currents in the range of ibcap,max = 5–10 mA. At
elevated bearing temperature Tb and/or low motor speed
n, where the bearing acts electrically primarily as an
ohmic resistance, the common mode voltage vcom causes
small bearing currents with amplitudes ibcap,max ≤
200 mA [15]. This type of bearing current is not discussed
any further, because of its much smaller amplitude when
compared with the other types of bearing currents.
2) At intact lubrication film, the bearing voltage vb mirrors
the common mode voltage vcom at the stator terminals
via the capacitive voltage divider “bearing voltage ratio.”
If the bearing voltage vb surpasses the threshold voltage
of the oil film between the balls and running surfaces
(approximately 5–30 V), the electrically loaded oil film
breaks down. This breakdown causes an electric discharge machining (EDM)-current pulse. Peak amplitudes
0278-0046/$25.00 © 2007 IEEE
MUETZE AND BINDER: PRACTICAL RULES FOR ASSESSMENT OF INVERTER-INDUCED BEARING CURRENTS
of the EDM-current pulse are ibEDM,max ≤ 0.5–3 A
(e.g., [8], [10], [14]).
3) The high dv/dt at the motor terminals—mainly because
of the stator winding-to-frame capacitance Cwf —causes
an additional HF ground current ig (also “common-mode
current”). This current excites a circular magnetic flux
around the motor shaft. This flux induces a shaft voltage
vsh along the shaft, and between the two bearings, of
the motor. If this voltage is large enough to puncture
the lubricating film of the bearing and destroy its insulating properties, it causes a circulating bearing current ibcir in the “stator frame–nondrive end–shaft–drive
end” loop. Peak amplitudes vary depending on the motor
size and are ibcir,max ≈ 0.5–20 A (Pr ≤ 500 kW)
(see, e.g., [5], [16], and [21]).
4) If the rotor is connected to earth potential (e.g., via the
mechanical load) with a significantly lower impedance
than the stator housing, part of the overall ground current
ig can pass the bearings as rotor ground current irg .
Bearing currents due to rotor ground currents can reach
considerable magnitudes with increasing motor size (see,
e.g., [17] and [21]) and destroy bearings within short time
of operation [5]. When such currents flow, they add to
potentially existing circulating bearing currents, where
the latter generally have the much larger dominating
amplitudes. In this case, however, the occurrence of EDM
currents is impeded, because the lubricating oil film no
longer has insulating properties. As a result, generally one
type of inverter-induced bearing current is dominating.
III. E NDANGERMENT OF B EARINGS BY
I NVERTER -I NDUCED B EARING C URRENTS
As the bearings of a machine depend on different parameters,
such as motor size, field of application, and conditions of operation, the significance of absolute values of bearing currents to
evaluate the endangerment of bearings is questionable. Therefore, in the context of “classical” bearing currents of large linefed machines that are mainly due to magnetic asymmetries, the
“apparent bearing current density” Jb is taken. Jb is defined by
Jb = ib,max /AH
(1)
where ib,max is the maximum amplitude of the total bearing
current, and AH is the Hertzian contact area given by the
elastic deformation of the balls or rolls of the bearing under
the mechanical pressure in practical operating conditions [23],
[24]. The calculation of AH is a complex task. However, for a
given machine, the value of AH can generally be obtained from
the bearing supplier.
In the context of direct current (dc) and low-frequency
alternating current applications (50/60 Hz), limits of apparent
bearing current densities have been taken from experience.
Summarizing different reports [25]–[29], bearing current densities Jb ≤ 0.1 A/mm2 do not influence the bearing life, and
bearing current densities Jb ≥ 0.7 A/mm2 may significantly
reduce the bearing life. As explained above, the frequencies of
inverter-induced bearing currents range from several hundred
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Fig. 2. Fluting of a bearing race as a result of inverter-induced bearing
currents, time of operation 1275 h, apparent bearing current density Jb ≤
2.0 A/mm2 , switching frequency fs = 10 kHz, squirrel-cage induction motor
with 11-kW rated power, and bearing type 6209 C3.
Fig. 3. Investigated parameters of a variable-speed drive system.
kilohertz to several megahertz and are thus much higher than
50/60 Hz. These bearing currents, too, can cause bearing fluting, thereby reducing the bearing life or causing bearing failure.
Fig. 2 shows the fluting of a bearing race that was caused by
inverter-induced bearing currents.
In [6], the bearing life with EDM and dv/dt currents is
projected by converting “classical” bearing current density
limits based on a mechanical model of the bearing contact
area. According to these authors, bearing current densities Jb ≤
0.4 A/mm2 do not degrade, Jb ≤ 0.6–0.8 A/mm2 probably do
not degrade, and Jb ≥ 0.8 A/mm2 can significantly endanger
the bearing life. A series of 22 test runs for bearing damage
assessment was carried out by the authors to further investigate
the influence of bearing current amplitude and type, calculated
apparent bearing current density, time of operation, and inverter
switching frequency on the bearing damage [30]. In these tests,
the degree of melting of the bearing race surface and the grade
of reduction of the carboxylic acid, which is an indicator of
the deterioration of the grease, were found to correlate with the
product of inverter switching frequency, time of operation, and
bearing current density. However, no clear correlation between
either the bearing current density, time of operation, or the
inverter switching frequency and the generation of a fluting
pattern is identified. Yet, the “conventional” threshold to failure
of Jb ≤ 0.1 A/mm2 was not shown to be wrong in these tests.
Except for these, statements on the mechanism of damage and
a threshold to failure under inverter supply are still missing, and
further research is needed.
In the meantime, as little is known about the dielectric and
tribologic explanations of the mechanism of damage inside
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IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 54, NO. 3, JUNE 2007
Fig. 4. Structure of the flowchart for bearing current determination.
the bearing, the “conventional” threshold to failure Jb ≤
0.1 A/mm2 is suggested as a rule of thumb, until further
knowledge is available.
IV. R ULES FOR S AFE M OTOR O PERATION
A. Introduction to the Developed Flowchart
Due to the cause-and-effect chains of the different types of
inverter-induced bearing currents, it is not a single parameter of
the drive system but the interaction of several parameters that
can cause flow of inverter-induced bearing currents. In practical
application in the field, many parameters can be unknown. In
such a context, extensive modeling can be impossible. Yet, it
is important to identify the flow of inverter-induced bearing
current as soon as possible, in order to predict the possible
endangerment of the drive system due to these phenomena, and,
if necessary, select appropriate mitigation techniques.
Numerous measurement results were obtained in the context
of a research program for systematic investigation of inverterinduced bearing currents [22]. This program included several
motors and inverters with power levels from 11 to 500 kW as
well as operation with numerous cables, filters, and bearings.
The investigations were conducted under exactly the same test
conditions for all configurations, using identical measurement
techniques and test setups. The measurement results obtained
in the frame of this research program are presented in a tutorial
way both quantitatively and qualitatively in [21]. The different
investigated parameters are summarized in Fig. 3.
In this paper, the measurement results of the research program are used as a starting point to propose a flowchart that
can serve as a tool to estimate the endangerment of a drive due
to inverter-induced bearing currents, where complex modeling
is not possible. Here, the problem identification is rewritten in
such a manner as to allow identification of the influence of
the different parameters of a given drive system and, thus, to
pave the way through the complex existing correlations. The
flowchart strongly builds on the fact that one out of the different
types of bearing currents will tend to dominate in a given drive
system, and identification of this current is therefore a critical
and decisive task. Fig. 4 shows an overview of the structure of
the flowchart, of which the individual blocks will be discussed
in detail subsequently.
Whereas the flowchart constitutes an alternative to physical
modeling of the phenomena, the relationships that underlie the
correlations outlined are supported by modeling that is based on
different physical parameters of the machines and their orders
MUETZE AND BINDER: PRACTICAL RULES FOR ASSESSMENT OF INVERTER-INDUCED BEARING CURRENTS
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Fig. 7. Checking of the influence of motor size.
Fig. 5.
Checking of the rotor grounding configuration.
Fig. 6. Measured bearing currents for grounded and ungrounded rotor with
use of shielded and unshielded motor cables of two 110-kW squirrel-cage
induction motors, bearing temperature Tb ≈ 70 ◦ C, motor cable length lc =
50 m, and 560-Vdc voltage-source inverter.
of magnitudes. The flowchart also summarizes possible means
to prevent bearing damage.
The focus of the proposed flowchart on the assessment of
inverter-induced bearing current should not confuse a broader
view of such an approach. As a matter of fact, it could serve as
a starting point for the development of an even more comprehensive tool for assessment including other inverter-related parasitic phenomena, such as electromagnetic interference (EMI)
and winding insulation failure.
B. Influence of the Rotor Grounding Configuration
The rotor grounding configuration is the first parameter of
influence considered because it determines whether harmful
ground currents can flow (Figs. 5 and 6). If the rotor is
not grounded, the flowchart has to be continued at step 2.
Otherwise, the type of motor cable, shielded or unshielded
motor cable, is of importance. If a shielded motor cable is
used and properly connected at both motor and inverter sides
with a 360◦ connection, the impedance of the stator housing
is generally low enough that hardly any rotor ground current
flows. If the grounding of the rotor cannot be eliminated and
shielded motor cable cannot be used, or if the shielded motor
cable is several hundred meters long, mitigation techniques for
bearing currents due to rotor ground currents should be applied
(Fig. 15). Otherwise, the flowchart can be continued at step 2.
Fig. 8. Measured bearing currents for variable motor speed n and bearing
temperature Tb , 11-kW squirrel-cage induction motor, 50-m unshielded motor
cable, and 560-Vdc voltage-source inverter.
C. Influence of the Motor Size
If no bearing currents due to rotor ground currents occur,
the size of the motor determines strongly whether EDM or
circulating bearing currents can occur (Figs. 7–10). This strong
significance of the motor size is due to the fact that the voltage
induced along the motor shaft vsh that can cause the flow of
the circulating bearing currents increases with the cube of the
motor frame size H [31], i.e.,
vsh = ig lfe ∼ H · H 2 = H 3
(2)
where the frame size H is defined as the distance between the
bottom of the motor housing feet and the center of the motor
shaft. As a matter of fact, vsh is proportional to the HF ground
current ig and the length of the stator core lfe , where lfe is
proportional to the machine size. The common mode current
ig is approximately proportional to the stator winding-to-frame
capacitance Cwf , which is proportional to the square of the
machine frame size H [32].
Drawing from analytical modeling of the flux distribution
and voltage generation [31], where the results are in line with
the experimental data, the machine frame sizes of 100 and
280 mm can be considered as rules of thumb for thresholds
to identify the bearing current type of likelihood. Accordingly,
for small machines with frame sizes of below approximately
100 mm, only EDM currents occur. For larger machines with
frame sizes of above 280 mm, circulating bearing currents
dominate, where the largest amplitudes occur at low motor
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IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 54, NO. 3, JUNE 2007
Fig. 9. Measured bearing currents for variable motor speed n and bearing
temperature Tb , 110-kW squirrel-cage induction motor, 50-m unshielded motor
cable, and 560-Vdc voltage-source inverter.
Fig. 11.
Estimation of the amplitude of circulating bearing currents.
Fig. 10. Measured bearing currents for variable motor speed n and bearing
temperature Tb , 500-kW squirrel-cage induction motor, 10-m unshielded motor
cable, and 560-Vdc voltage-source inverter.
speed. Both types of bearing currents can occur at machines
with frame sizes between 100 and 280 mm, but the general
tendency is for circulating bearing currents to increase with
frame size.
The amplitude of the circulating bearing current ibcir,max
can be estimated from the HF ground current ig of the motor.
This is done in step 3 of the flowchart (Section IV-C). The
situation is different in the case of EDM bearing currents, where
further calculation requires knowledge of many parameters
of the drive. Generally, the endangerment of the bearings is
likely to increase with the reduction of the motor size because
of the decrease of the contact area AH in the bearings. No
further estimations are possible at this point, and it has to be
decided whether mitigation techniques should be applied or
not (Fig. 15).
D. Estimation of the Amplitude of the Circulating Current
With the HF ground current ig being the driving force of
the circulating bearing current, the circulating bearing current
ibcir,max can be estimated from the amplitude of the ground
current ig,max . To this aim, the analytical model for the flux
distribution can be extended to derive an equivalent circuit
for the HF circulating bearing current generation including the
influence of electrically insulated bearings of different thick-
Fig. 12. Measured bearing currents with use of different bearings, 500-kW
squirrel-cage induction motor, bearing temperature Tb ≈ 70 ◦ C, 2-m shielded
motor cable, and 560-Vdc voltage-source inverter; measured HF ground current
105 A (pk-to-pk) (DE/NDE: drive/nondrive end).
nesses [32]. From this circuit, upper limits for the amplitude of
the circulating bearing current as a function of the HF ground
current are derived (Fig. 11) as follows:
• two conventional bearings
ibcir,max ≤ 0.4 · ig,max
(3)
• one insulated, one conventional bearing
ibcir,max ≤ 0.2 · ig,max
(4)
• two insulated bearings
ibcir,max ≤ 0.1 · ig,max
(5)
• one or two hybrid bearings
ibcir ≈ 0.
(6)
It has to be noted that these relationships are upper limits,
and the occurring ratios ib,max /ig,max are often much smaller
by more than a factor of two (Fig. 12).
MUETZE AND BINDER: PRACTICAL RULES FOR ASSESSMENT OF INVERTER-INDUCED BEARING CURRENTS
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Fig. 13. Estimation of the amplitude of the ground current.
If the amplitude of the ground current ig is unknown, it has
to be measured by experts or estimated; otherwise, the use of
mitigation techniques for circulating bearing currents has to
be considered (Fig. 15). As a rule of thumb, the estimation of
the amplitude of the HF ground current ig,max can be done as
follows (Fig. 13): The amplitude ig,max depends strongly on
the Cwf and the dv/dt of the line-to-ground voltage vLg at the
motor terminals [32]. The value of Cwf can either be measured
or estimated using
Cwf = 0.00024 · H 2 − 0.039 · H + 2.2
(7)
where Cwf is given in nanofarads, and H is the machine frame
size in millimeters.
If the value of dv/dt of the line-to-ground voltage vLg is
unknown, it needs to be measured or estimated. The exact
calculation of the HF ground current is difficult, as the HF
behavior of the machine needs to be known. However, for the
present context, only an estimation of the HF ground current
amplitude is aimed for. Thus, the extensive set of measurement
data obtained in the context of the research program [22]
is used to experimentally derive correlations between ig,max ,
Cwf , and dvLg /dt. In this approach, the cases with dvLg /dt
larger, equal, or smaller than 0.5 kV/µs are distinguished.
In addition, “electrically long” and “electrically short” motor
cables are differentiated. A cable is considered as “electrically
long” if the cable length lc is equal or larger than the “critical
cable length” lc,crit , i.e., lc ≥ lc,crit . The critical cable length
lc,crit is given by the velocity of electromagnetic waves in the
cable (“cable velocity”) vcable and the rise time of the voltage
pulse tr , i.e.,
lc,crit = 0.5 · vcable · tr
(8)
where the value of the cable velocity vcable is approximately
150 · 106 m/s. With these preliminary distinctions, the amplitude of the HF ground current ig,max can then be estimated as
follows:
• dvLg /dt > 0.5 kV/µs
–
electrically long motor cable
ig,max ≤ 1.5 · 2/3 · dvLg /dt · Cwf
(9)
Fig. 14. Measured ground and bearing currents with use of different filters
of two 500-kW squirrel-cage induction motors, motor speed n = 15 r/min,
bearing temperature Tb ≈ 70 ◦ C, 10-m shielded motor cable, and 560-Vdc
voltage-source inverter.
–
electrically short motor cable
ig,max ≤ 1.5 · dvLg /dt · Cwf
(10)
• dvLg /dt ≤ 0.5 kV/µs
ig,max ≤ dvLg /dt · 2 · Cwf .
(11)
E. Mitigation Techniques
As the cause-and-effect chains of the different bearing current phenomena are different, mitigation techniques have to
be chosen according to the type of bearing current that shall
be reduced or eliminated. With the common source of all
inverter-induced bearing currents being the HF common-mode
voltage of the inverter, all mitigation techniques that eliminate
the common-mode voltage of the inverter eliminate inverterinduced bearing currents. In a similar way, if the number of
occurrences of inverter-induced bearing currents is reduced by
filter or control patterns that reduce the common mode voltage,
the bearing damage can possibly be delayed [30].
Brushes and conductive bearing grease have also been suggested to reduce EDM bearing currents. However, the maintenance of the brushes in order to maintain good electrical contact
at high frequencies can be difficult. In a similar way, it has to be
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IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 54, NO. 3, JUNE 2007
Fig. 15. Mitigation techniques for different types of inverter-induced bearing currents.
assured that the conductive lubricating grease also has adequate
mechanical properties.
Bearings other than conventional steal bearings, hybrid or
ceramic bearings with ceramic rolling elements eliminate all
inverter-induced bearing currents, because the whole rolling
element diameter is electrically insulating. It provides an impedance in the bearing current paths that is high enough to
completely eliminate the inverter-induced bearing currents.
Electrically insulated bearings with sufficient thickness of the
insulating layer (at least 250 µm) can effectively reduce circulating bearing currents and bearing currents due to rotor ground
currents, but not EDM bearing currents.
Filters that do not eliminate the common-mode voltage can
mitigate circulating bearing currents and bearing currents due to
rotor ground currents, but not EDM bearing currents (Fig. 14).
Fig. 15 summarizes different mitigation techniques for different
types of inverter-induced bearing currents as they have been
suggested in the literature and in the aforementioned research
program (see, e.g., [2], [5], [7]–[11], [13], [14], [17]–[21],
[33], and [34]). Condition monitoring techniques, such as, for
example, proposed in [35] and [36], are beyond the scope of this
figure and of this paper, as we focus on practical rules that are
to be applied before a drive is installed and taken into operation.
V. C ASE E XAMPLE
A case example is included in this paper in order to illustrate
the use of the proposed method. The case example lends itself
to one of the many inquiries of field engineers who investigate
the possibility of occurrence of bearing damage-prone inverterinduced bearing currents.
Given is an inverter-driven 200-kW four-pole squirrel-cage
induction motor with a frame size of 315 mm. The field
engineer has been offered electrically insulated bearings by the
bearing manufacturer. Thus, he would like to investigate the
possible use of this mitigation technique both with regard to
necessity and adequacy.
First, the grounding configuration of the rotor is determined.
As the load is coupled to the drive via an insulated coupling, and
no other grounding connections of the shaft can be identified,
the possibility of occurrence of bearing currents due to rotor
ground currents is excluded. Because of the frame size of the
machine, EDM bearing currents are not likely to cause any
bearing damage, but the endangerment of the bearings due to
circulating bearing currents is investigated in more detail.
The field engineer cannot measure the stator winding-toframe capacitance. However, the dv/dt of the line-to-ground
voltage at the motor terminals is measured to be dvLg /dt =
1.7 kV/µs. The stator winding-to-frame capacitance is calculated from the motor frame size, where Cwf = [0.00024 ·
(315)2 − 0.039 · 315 + 2.2] nF = 13.7 nF according to (7).
The machine is connected with short motor leads of less than
2 m, so that the motor cable is electrically short. Using these
preliminary results, the HF ground current is estimated from
(10), i.e., ig,max ≈ 1.5 · 1.7 · 13.7 A = 35 A. Using (3)–(5),
the upper bound for the bearing current amplitude is determined as ib,max ≈ 14, 7, and 3.4 A with none, one, and
two insulated bearings, respectively. The bearing manufacturer
has supplied the calculated value of the Hertzian contact
area AH = 17 mm2 from which the upper bound for the
apparent bearing current density is calculated, i.e., Jb,max ≈
0.82, 0.41, and 0.21 A/mm2 for the different choices of bearings, respectively. According to these calculations, the bearing
current density is larger than Jb = 0.1 A/mm2 . However, these
calculations give upper limits, and often the values are smaller
by a factor of two. In addition, the switching frequency of the
inverter is as low as 2 kHz. Thus, the field engineer decides
to operate the drive with two electrically insulated bearings,
MUETZE AND BINDER: PRACTICAL RULES FOR ASSESSMENT OF INVERTER-INDUCED BEARING CURRENTS
anticipating that the set of parameters will not push the bearing
load beyond the threshold to failure.
VI. S UMMARY
A flowchart that can serve as a tool to assess the endangerment of bearings due to inverter-induced bearing currents
is proposed, where many parameters of a drive are unknown
and complex modeling is not possible. The flowchart draws
from numerous measurement results that have been obtained in
the context of a research program for systematic investigation
of inverter-induced bearing currents, identification of key parameters via analytical approaches, and results that have been
published in the literature.
First, the grounding configuration of the rotor is classified in
order to determine whether bearing currents due to rotor ground
currents can flow. Next, the size of the motor is considered,
because this parameter largely determines whether EDM or
circulating bearing currents can flow. This step is followed
by an assessment of the amplitude of the circulating bearing
current as a function of the HF ground current. A rule of thumb
for the estimation of the HF ground current is also given. At the
end, the chart summarizes the different mitigation techniques
to prevent bearing damage due to inverter-induced bearing
currents.
The flowchart can be very useful when first discussing the
bearing current phenomena and identifying if a given drive
system, including the given operating conditions, falls into an
area where bearing damage due to inverter-induced bearing
currents can occur. In the future, drawing from the numerous
results presented in the literature on other phenomena that are
related to inverter operation, such as EMI and winding insulation failure, the flowchart can be extended to include assessment
of these phenomena. Thus, the flowchart can serve as a starting
point for the development of an even more comprehensive tool
for the assessment of inverter-related parasitic phenomena in
inverter-based drive systems.
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1622
Annette Muetze (S’03–M’04) received the
Dipl.-Ing. (diploma) degree in electrical engineering from Darmstadt University of Technology,
Darmstadt, Germany, the diploma in general engineering from Ecole Centrale de Lyon, Lyon,
France, in 1999, and the Dr. Tech. (Ph.D.) degree
in electrical engineering from Darmstadt University
of Technology in 2004 (under the supervision of
Prof. A. Binder).
From 2004 to 2006, she was an Assistant Professor
in the Department of Electrical and Computer Engineering, University of Wisconsin, Madison. Since January 2007, she has been a
Lecturer in the School of Engineering, University of Warwick, Coventry, U.K.
Prof. Muetze was the recipient of the FAG Innovation Award 2004 for her
work on inverter-induced bearing currents and a National Science Foundation
CAREER Award in 2005.
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 54, NO. 3, JUNE 2007
Andreas Binder (M’97–SM’04) received the
Dipl.-Ing. (diploma) and Dr. Tech. (Ph.D.) degrees
in electrical engineering from the University of
Technology, Vienna, Austria, in 1981 and 1988,
respectively.
From 1981 to 1983, he was with ELIN-Union AG,
Vienna, where he worked on the design of synchronous generators. From 1983 to 1989, he was with
the Department of Electrical Machines and Drives,
Technical University, Vienna. After this, he joined
Siemens AG, first in Bad Neustadt, Germany, then
in Erlangen, Germany. His main tasks included the development of dc and
inverter-fed ac drives. Since October 1997, he has been the Head of the
Institute of Electrical Energy Conversion, Darmstadt University of Technology,
Darmstadt, Germany, where he is also a Full Professor.
Dr. Binder was the recipient of the Power Engineering Society (ETG)
Literature Award in 1997.