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IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
Arc Movement Inside an AC/DC Circuit Breaker
Working With a Novel Method of Arc Guiding:
Part I—Experiments, Examination, and Analysis
Harald Hofmann, Christian Weindl, Malik I. Al-Amayreh, and Ove Nilsson
Abstract—Within this project, the mode of operation of the
circuit breaker and its new innovative method of arc guiding were
analyzed and verified. The solution refers to a switching device
that is able to deal with both ac switching loads and bidirectional
dc switching loads. It is primarily intended for use in UIC-capable
switching units for voltages up to 3 kV and currents up to 800 A.
The concept uses a combination of permanent and electromagnetic
blowout fields. This completely new and innovative approach
is intended to permit activation of the blast coils by the arcs
themselves to generate the electromagnetic blowout fields without
need for additional electrical switching contacts. The combining
of a newly developed optical data acquisition system together
with the conventional recording of electrical parameters made the
verification of the working hypothesis of the switching process
possible. A numerical model is used for the simulation of the
later stage of the extinguishing process, where the arc is driven
toward the arcing chamber by the superposed magnetic fields of
permanent magnets and blast coils, until it is extinguished due
to elongation and cooling by the arc splitter stack. The results
of the measurement data analysis and theoretical modeling and
simulation of the extinguishing process led to the identification of
critical operational areas and resulted in a successful optimization
of the contactor.
Index Terms—Arc guiding, circuit breaker, electrical contactor,
ionized gas guiding, thermal plasma.
I. I NTRODUCTION
F
OR a long time, requests for the development of circuit
breakers that are able to break ac currents as well as dc
currents have been made. The difficulty herein is to achieve a
complete extinction of the arc at shutoff cycle for both types of
load. Within dc circuit breakers, permanent magnets are usually
used to generate a specific magnetic field that forces the arc to
move toward the arcing chamber. In the arcing chamber, the
elongation or splitting of the arc and its extinction by cooling
are achieved by the use of fan-shaped plates made of ceramic
Manuscript received December 22, 2011; accepted February 20, 2012. Date
of publication June 18, 2012; date of current version August 7, 2012. This
work was supported by the Bavarian Research Foundation under the reference
number AZ 746-07.
H. Hofmann and C. Weindl are with Lehrstuhl für Elektrische Energieversorgung, Universität Erlangen, 91058 Erlangen, Germany (e-mail:
hofmann@eev.eei.uni-erlangen.de; weindl@eev.eei.uni-erlangen.de).
M. I. Al-Amayreh is with Lehrstuhl für Strömungsmechanik, Universität Erlangen, 91058 Erlangen, Germany (e-mail: malik.amayreh@lstm.
uni-erlangen.de).
O. Nilsson is with Schaltbau GmbH, 81829 München, Germany (e-mail:
nilsson@schaltbau.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/TPS.2012.2200697
or metal [1]. Due to the use of permanent magnets, the function
of the circuit breaker depends on the polarity of the current.
If a reverse current were to be applied to the switch, the arc
would move into the opposite direction, away from the arcing
chamber. AC circuit breakers, on the other hand, generally use
an electromagnetically generated blowout field because, at ac
currents, the polarity of the current changes with every half
sine wave. The coils used to produce this blowout field are
connected to the same electrical circuit as the contactor itself
so that the magnetic field and the arc oscillate in phase because
→ −
−
→ −
→
of the resulting electromagnetic force F = B × I . The result
of this approach is that the arc is driven into the arcing chamber,
regardless of the polarity of the current. A disadvantage of the
electromagnetic blowout in normal operation, however, is the
permanent current conduction and the resulting heating of
the blast coils. Another problem arises for the breaking of small
currents because the strength of the magnetic field generated is
not strong enough to drive the arc into the arcing chamber [2].
The problem of the permanent activation of the coils can be
solved by using leading contacts [3]. This design can achieve
the activation of the blast coils shortly before the release of the
main contacts. Unfortunately, this technical approach has not
performed very reliably in practice. Here, the development of a
contactor with a novel method of arc guiding is managed, which
is able to deal with both ac switching loads and bidirectional
dc switching loads [4]. It is primarily intended for use in UICcapable switching units for voltages up to 3 kV and currents
up to 800 A. The concept uses a combination of permanent
magnetic and electromagnetic blowout fields. This completely
new and innovative approach is intended to permit the activation of the blast coils by the arcs themselves to generate
the electromagnetic blowout fields without need for additional
electrical switching contacts.
Fig. 1 illustrates the basic working hypothesis of the contactor. The moving contact separates from the two fixed contacts,
and an arc arises between the moving contact and each of the
fixed contacts. The two fixed contacts are mounted in a defined
distance to the arc-guiding rails. The two arcs are deflected horizontally in the same direction by the permanent magnetic fields
[5]. The arc moving inward commutes from the fixed contact to
the arc-guiding rail and activates the first electromagnetic blast
coil, which generates an electromagnetic field that deflects the
arc in vertical direction. The arc commutates to the opposite
arc-guiding rail, whereby the second blast coil, which generates
an electromagnetic field with the same direction, is activated.
The arc moving outward extinguishes due to the contact link
0093-3813/$31.00 © 2012 IEEE
HOFMANN et al.: ARC MOVEMENT INSIDE AN AC/DC CIRCUIT BREAKER—PART I
Fig. 1.
Stages of the switching operation. Phase 1: Ignition. Phase 2: Commutation. Phase 3: Migration.
Fig. 2.
Regions and associated positions of the optical fibers.
going dead. The remaining arc is accelerated in the vertical
direction and driven into the arcing chamber [6], where it is
extinguished due to elongation and cooling. The aim of this
project was to verify the movements of the arcs and to optimize
the design of the contactor.
II. E XPERIMENTALS
A. Test Setup
The task includes the detection and modeling of the arc
movement inside the circuit breaker resulting from the switching process and the verification of the working hypothesis of
the contactor. The voltage and current waveforms as well as
the positions of the arcs have to be recorded at any time of the
switching process to be able to prove the functional principle by
experiment. Light detectors in conjunction with optical fibers
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have shown very good performance for the investigation of arc
position and arc movement [7]. A new optical measurement
system, based on photodetectors with transimpedance amplifiers, which are connected to the device via optical fibers, was
developed and successfully tested. For the first time, the recording of the position, intensity, and propagation characteristics
of the arcs within the switch with high temporal and spatial
resolution could be achieved with this device. Holes had to be
drilled into the case of the circuit breaker at defined positions
where the optical fibers are inserted. The positions of the holes
were selected to achieve maximum technical and scientific
knowledge from the readings of the photodetectors as well as
minimum possible attenuation of the magnetic field. The device
had to be divided into defined regions, each of them assigned to
a specific stage of the switching process, to simplify the evaluation of the different stages of the switching process (see Fig. 2).
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Fig. 3. Tapping of the electrical and optical signals.
For preliminary investigations, the power for the test circuit
was supplied by the battery system of the Institute for Electrical
Energy Supply of the University of Erlangen, which has a noload voltage of 436 V and a short-circuit current of 5800 A. Due
to the limited voltage of the battery system, the existing highpower ac system at the department, which provides a threephase adjustable output voltage in the range of 52–250 V with a
maximum output current of 40 kA, has been extended to supply
the voltages and currents needed for the inspections and tests.
An additional transformer is used to convert the output voltage
range of the high-current system to the operating voltage range
of the contactor. Depending on the wiring, voltages up to 8 kV
at currents up to 1.4 kA or 4 kV at currents up to 2.8 kA
can be provided. The current limitation is done via external
impedances on the primary side of the transformer. To be able to
use the large current and voltage range of this configuration for
dc tests as well, a diode bridge rectifier was developed, which
is composed of 24 single high-power diodes and matching heat
sinks. Each diode is rated for a continuous current of 830 A at
a reverse voltage of 5 kV. The three-phase construction of the
rectifier with four diodes per string allows the interconnection
of the diodes either for maximum reverse voltage (5 kV ×
4 = 20 kV), maximum current (830 A × 4 = 3.32 kA), or
combined (10 kV, 1.66 kA). The output voltage can be adjusted
in the range of 1–11 kV and has a ripple of less than 13.4%
without smoothing. The entire system is protected by surge and
overvoltage arresters at the input and output.
B. Data Acquisition
Measurement systems, which are able to acquire the voltage
and current waveforms as well as the light emissions at specific
points of the device, are used to determine a correlation between
the electrical parameters and the migration of the arc within
the specimen. The electrical parameters are recorded with an
IMC Polares universal meter for power measurement, and
light emissions are recorded with photodetectors and a highspeed camera. All measurement systems are synchronized by a
common trigger signal to provide synchronized time stamps for
data acquisition. A LabView application is used for recording,
visualization, and analysis of the measured data. The measurement setup is shown in Fig. 3.
It is essential to record electrical measurement data from
inside the switch to be able to do a detailed analysis of the
switching process. Thus, the internal connections from the blast
coils to the arc-guiding rails are cut and redirected to the
outside. High-voltage dividers are used to adapt to the inputvoltage range of the data acquisition system. Because of the
potential-free current measurement via Hall effect transducers
and the common ground of the high-voltage dividers, there is
no need to use isolating amplifiers. The waveforms of the coil
currents and voltage potentials of the coils and arc-guiding rails
as well as the overall current and voltage can be determined
with this test setup. Additional data such as arc voltage and arc
power as well as the strength and shape of the magnetic field
can be derived from the measured values [8].
The measurement of light emissions is performed via Si PIN
photodetectors, which are connected to the device under test via
optical fibers. A total of 96 holes are drilled into the case of the
test sample at defined positions to hold the optical fibers. Due
to the very low output voltages and the large internal resistance
of the photodetectors, transimpedance amplifiers are used for
coupling with the data acquisition system. Two 16-channel data
acquisition systems with a sampling rate of 50 kHz are used
for capturing of the signal shapes, so up to 32 photodetector
signals can be recorded simultaneously. Both the intensity of
the arc and its propagation speed can be determined from the
acquired data. The advantages of the optical measurement by
HOFMANN et al.: ARC MOVEMENT INSIDE AN AC/DC CIRCUIT BREAKER—PART I
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and then, the speed decreases continuously until the arc finally
stays at the position of the permanent magnet (see Fig. 6).
The different voltage levels in Fig. 6 result from the different
spatial distances between the arc and the optical fiber head of
the corresponding hole.
Stage 2: Commutation of the Inner Arc Into the Coil Channel
Fig. 4.
Current and voltage characteristics of the switching process.
photodiodes are short response time (< 50 ns), which allows
good temporal resolution of the signals, and a wide dynamic
range, so that very weak signals still can be resolved well,
whereas very bright signals do not lead to saturation. However,
the number of input points is limited due to the fact that
each photodetector requires a separate amplifier and a separate
channel on the data acquisition system. In order to overcome the
disadvantage of limited spatial resolution due to the small number of photodetectors, parallel recording of the arc migration is
performed with a high-speed camera. The camera used is capable of recording 10 000 images per second with a resolution of
512 × 192 pixels. Thereby, the arc migration can be observed,
but a detailed analysis of the intensity and propagation speed
of the arc is only possible to a limited extent due to the limited
dynamic range and smearing effect of the camera.
III. R ESULTS
Several sets of experiments with different types of voltage
and current loads were performed. The load was varied to be
able to determine the switching characteristics over the entire
operating range. For detailed analysis of each stage of the
switching operation (ignition, commutation, migration, and extinction), it is necessary to assign a defined area of the contactor
to each of the stages. The contactor is divided into different
regions, in which a particular stage of the switching process can
be observed (see Fig. 2). Each area of the specimen is visualized
in a separate window within the LabView application. This
allows the direct observation of the influence of load and parameter changes to the different stages of the switching process.
In Fig. 4, the curves of breaking a current of 280 A at 3.6 kV ac
are shown. The contacts of the switch separate at t = 80 ms.
Stage 1: Ignition of the Arcs and Deflection by the Permanent
Magnetic Field
The ignition and vertical migration of the two arcs can be
observed within regions 1A and 1B (see Fig. 5). The deflection
of the two arcs is solely caused by the permanent magnetic
field in the horizontal direction. The inward shifting arc (region
1B) initially moves with a speed of 20 m/s, which raises up
to 40 m/s at commutation to the arc guide rail. The outward
shifting arc (region 1A) moves at first with a speed of 20 m/s,
The inner arc commutes onto the arc guide rail and is
expanding into the right coil channel (region 2AB; see Fig. 7).
The propagation speed is initially at 90 m/s and decreases until
the arc reaches the blast coil at a speed of 45 m/s (see Fig. 8).
By reignition, the regions are also passed several times. Fig. 8
displays the first reignition within this switching process.
Stage 3: Expansion of the Arc Into the Arc Splitter Stack
The arc in the coil channel has died out because the voltage
on the blast coils has dropped below the required arc voltage.
Because of the electrical potential between the arc-guiding
rails, the arc ignites in area B. Now, the total current is flowing
through both of the blast coils and the arc and produces a
magnetic field that deflects the arc horizontally toward the
splitter plates. The propagation speed is about 120 m/s in
the range of the sensors. At this point, it becomes plainly
visible that the propagation characteristics of the arc can only
be determined with access to a high temporal and spatial
resolution. Despite the very high frame rate of the high-speed
camera of 10 000 frames/s and the very short exposure time of
50 μs, the position of the arc is no longer uniquely determined
within single frames (see Fig. 9). The arc migration, however,
can still be resolved well by the photodetectors with their short
response and decay time and the high sampling rate of the data
acquisition system (see Fig. 10).
IV. I DENTIFICATION OF C RITICAL
O PERATING C ONDITIONS
Due to the fact that the electromagnetic blowout force is
directly dependent on the current flowing through the blast
coils and because of the current dependence of the arcs’ own
magnetic field [9], it becomes evident that the force on the arc
is very limited at low currents. Only a small arc was observed
in the test when breaking low currents (< 10 A) at a voltage of
2.5 kV dc. After raising the voltage to 3.6 kV, slowly moving
arcs were detected within the region of the contacts, sometimes
commuting to the coil channels. The arcs moved along the
edge of the contact bridge, as described in [10], and led to the
outgassing of the plastics at the inner walls of the contactor
housing. As a result, the switching times and, thus, the time
that the arcs resided at the predamaged walls increased from
time to time until it finally led to a fire exit from the vent of the
circuit breaker due to burning plastic (see Fig. 11).
V. O PTIMIZATION OF THE C ONTACTOR
The results of the investigation of the critical operational conditions required a modification of the test object,
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IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
Fig. 5. Deflection of the arcs caused by the permanent magnetic field.
Fig. 6. Photodetector signals of regions 1A and 2A.
Fig. 7. Migration of the inner arc within the coil channel.
particularly to ensure that the switch is not damaged while cutting off low currents. As a solution, a ceramic plate was placed
at those areas of the switch where outgassing of the plastic
had occurred. To ensure that the modification of the contactor
has no adverse effects on the ultimate breaking capacity, the
measurements taken with the unmodified version were repeated
with the modified version. It was observed that, within the
measurement accuracy, the modification has no effect on the
switching process when breaking high currents. The analysis
of the performance at low currents showed that the switching
times increased even after the modification from time to time.
The switching operations were performed at 5-min intervals
with a voltage of 3.6 kV dc and a current of 10 A. The switching
time increased from 50 ms initially to over 1 s at the eighth
switching operation. After an idle time of 3 h, the experiment
was repeated. The first breaking also took 50 ms, and further
operations again showed a significant increase in switching
times. Further experiments showed that low switching times
can be achieved again by blowing out the test item. After each
switching operation, compressed air was blown through the
HOFMANN et al.: ARC MOVEMENT INSIDE AN AC/DC CIRCUIT BREAKER—PART I
Fig. 8.
Photodetector signals of region 2AB.
Fig. 9.
Migration of the arc within the expansion channel.
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Fig. 10. Photodetector signals of regions B and C.
sample for 30 s, and the switching times were back at 50 ms.
Apparently, the blowing will remove conductive substances that
accumulate inside the device with every breaking operation, so
further improvement of the contactor may be achieved by using
an improved arc gas venting system [11].
VI. M ODELING AND S IMULATION
Fig. 11. Fire resulting from a nonmoving arc at a switching operation with
critical current.
The mathematical modeling of flow and heat transfer within
the contactor is based on the basic equations of fluid mechanics
(Navier–Stokes equations) and the energy balance equations.
These equations contain different mass, momentum, and
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IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
energy transport processes, including the convective transport
of mass, momentum, and energy, the diffusive transport of
mass, momentum, and energy, and the thermal radiation. Moreover, the Maxwell equations in conjunction with the covering of
chemical effects are taken into account. The numerical solution
of these equations is calculated by means of the finite volume
method. The results of the modeling and the simulation are
shown in part 2.
ACKNOWLEDGMENT
The authors would like to thank R. Kralik who invented
the contactor studied and his colleague A. Ignatov for the
prototypes and advice regarding the experiments.
Christian Weindl was born in Nürnberg, Germany,
in 1965. He received the Dipl.Ing. degree in electrical
engineering from the Friedrich-Alexander University
Erlangen-Nürnberg, Erlangen, Germany, in 1993 and
the Dr. Ing. degree (cum laude) from the Institute
of Electrical Power Systems at the University of
Erlangen-Nürnberg, Erlangen, in 1999/2000.
He worked in the High-Voltage Transmission and
Distribution Department (Group System Planning)
of Siemens AG, Erlangen, from 1993 to 1995 and
joined the Institute of Electrical Power Systems at
the University of Erlangen-Nürnberg in 1994. His primary research interests
are harmonic stability, control of converters and FACTS equipment, and the
interactions of these devices with the surrounding network. Since 2005, he has
headed an international project in the field of the artificial aging of power cables
and the estimation of the remaining lifetime of electrical distribution systems.
In 1999, one of his papers won the literature award of ETG/VDE, and in
2002, his Ph.D. work was awarded a research price by a major German utility
(E-ON Bayern AG).
R EFERENCES
[1] K. Nakano and K. Takemura, “Circuit breaker with an arc suppressor,”
Eur. Patent FR2 465 308, May 13, 1981.
[2] J. G. J. Sloot and G. M. V. Bosch, “Some conditions for arc movement
under the influence of a transverse magnetic field,” Holectechniek, vol. 3,
pp. 98–106, 1972.
[3] F. Hollmann, “Mittelspannungs-Lasttrennschalter,” Eur. Patent
DE3 332 684, Oct. 9, 1983.
[4] R. Kralik, “Schütz für Gleichstrom- und Wechselstrombetrieb,” Eur.
Patent DE 102 006 035 844, Feb. 6, 2008.
[5] T. E. Browne, Circuit Interruption—Theory and Technique. New York:
Marcel Dekker, 1984, pp. 641–679.
[6] N. Behrens, “Arc motion between opening and diverging electrodes,” in
Proc. Conf. Elect. Contact Phenom., 1978, pp. 243–247.
[7] J. W. McBride and P. M. Weaver, “High speed and medium resolution arc
imaging,” in Proc. 17th ICEC, 1994, pp. 113–119.
[8] P. M. Weaver and J. W. McBride, “Magnetic and gas dynamic effects on
arc motion in miniature circuit breakers,” in Proc. 39th IEEE Holm Conf.
Elect. Contacts, 1993, pp. 77–85.
[9] R. Michal, “Theoretical and experimental determination of the
self-field of an arc,” in Proc. 26th Holm Conf. Elect. Contacts, 1980,
pp. 265–270.
[10] P. E. Secker and A. E. Guile, “Arc movement in a transverse magnetic field
at atmospheric pressure,” Proc. Inst. Elect. Eng. A—Power Eng., vol. 106,
no. 28, pp. 311–320, Aug. 1959.
[11] J. W. McBride and P. A. Jeffery, “The design optimisation of current
limiting circuit breakers,” in Proc. IC-ECAAA Conf., 1997, pp. 354–360.
Harald Hofmann was born in Nürnberg, Germany,
in 1968. He received the Dipl.Ing. degree in electrical
engineering from the Friedrich-Alexander University
Erlangen-Nürnberg, Erlangen, Germany, in 2002.
In the same year, he was recruited by the Modern
Drive Technology GmbH as a Designing Engineer
and became the Head of development in 2005. He
joined the Institute of Electrical Power Systems at
the University of Erlangen-Nürnberg in 2008. His
primary research interests are electrical measurement engineering, switching behavior of ac/dc circuit
breakers, and novel measurement methods for the estimation of the remaining
lifetime of electrical distribution systems.
Malik I. Al-Amayreh was born in Erlangen,
Germany, on October 09, 1981. He received the B.S.
degree and the M.S. degree (with honor) from the
Mechanical Engineering Department, University of
Jordan, Amman, Jordan, in 2004 and 2007, respectively. He is currently working toward the Ph.D.
degree in the Institute of Fluid Mechanics, University of Erlangen-Nürnberg, Erlangen, and is awarded
with an Alexander Mayer scholarship.
In 2007 to 2008, he was a Lecturer in the Engineering Technology College at AlBalqa Applied
University, Salt, Jordan. In 2008 to 2010, he worked as a Researcher in the
Institute of Fluid Mechanics (LSTM) at the University of Erlangen-Nürnberg.
His research interests include the applications of the flow field ionized gases
and gasification of oil shale using plasma.
Mr. Al-Amayreh is a member of the European Mechanics Society.
Ove Nilsson was born in Tavelsjö, Sweden, in 1956. He received the B.Sc.
degree in material physics from the University of Umeå, Umeå, Sweden, in
1980 and the Ph.D. degree from the Department of Experimental Physics,
University of Umeå, in 1986.
At the Department of Experimental Physics at the same university, he did
his doctorate developing a new hot-wire method for the determination of
thermal conductivity and heat capacity under high pressure. From 1987 to
1991, he was a Post-doc at the University of Würzburg, Würzburg, Germany,
continuing in the field of thermal physics. In 1992, he joined the newly founded
Bavarian Center of Applied Energy Research, Würzburg, where he worked as
an Administration Manager and Scientist until 1998. After a period as Sales
Manager for Vitec GmbH, Würzburg, he joined Schaltbau GmbH, Munich,
Germany, in 2001, where he currently works as a Research Engineer. The
company produces contactors, snap-action switches, connectors, and master
controllers.