IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
2035
Arc Movement Inside an AC/DC Circuit Breaker
Working With a Novel Method of Arc Guiding:
Part II—Optical Imaging Method and
Numerical Analysis
Malik I. Al-Amayreh, Harald Hofmann, Ove Nilsson, Christian Weindl, and Antonio R. Delgado
Abstract—This paper aims at understanding the design concept
and behavior of the ionized gases inside a new electrical contactor.
The switching device is designed for ac and dc operations up to
3.5 kV and nominal currents up to 800 A. The contactor consists of
five electrodes: two anodes, two cathodes, and a moving electrode
or bridge which works as an anode and a cathode simultaneously.
In order to increase the safety, the electrical contactor includes
two contact points. The line current can be diverted into an arc
between the electrode and the bridge and an arc between the runner electrodes. The movement of the ionized gases is controlled by
two permanent magnets and two coils installed near the electrodes.
The arc plasma itself feeds the coils with current. The arc plasma
velocity increases if more current is allocated in the arc plasma.
The dynamics of ionized gases in the contactor is analyzed using
two optical methods, viz., optical imaging method and high-speed
camera (HSC). The optical imaging software has been developed
to generate dynamic images of the high-speed ionized gases at a
rate of 50 000 frames/s. The results of this method have been compared with those obtained using an HSC. A transient numerical
model has been developed to simulate the arc plasma inside the
main runner for the case of dc current. The properties of the air
plasma are considered variable with temperature and pressure.
The calculation shows the position and temperature of the arc
plasma as a function of time.
Index Terms—Arc plasma simulation, electrical contactor,
optical imaging method.
N OMENCLATURE
A
B
Vector magnetic potential (in volt seconds per
meter).
Magnetic flux density (in teslas).
Manuscript received December 22, 2011; revised March 12, 2012; accepted
May 8, 2012. Date of publication June 18, 2012; date of current version
August 7, 2012. This work was supported by the Bayerische Forschungsstiftung
under project AZ 746-07.
M. I. Al-Amayreh and A. R. Delgado are with the Institute of Fluid
Mechanics (LSTM), Friedrich-Alexander University of Erlangen–Nuremberg,
D-91058 Erlangen, Germany (e-mail: malik.amayreh@lstm.uni-erlangen.de;
Antonio.Delgado@lstm.uni-erlangen.de).
H. Hofmann and C. Weindl are with the Institute of Electrical Power
Systems, Friedrich-Alexander University of Erlangen–Nuremberg, 91058
Erlangen, Germany (e-mail: hofmann@eev.eei.uni-erlangen.de; weindl@
eev.eei.uni-erlangen.de).
O. Nilsson is with Schaltbau GmbH, D-81829 Munich, 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.2012.2200698
cP
D
Specific heat (in joules per kilogram kelvin) .
Dielectric displacements (in ampere seconds per
square meter).
E
Electrical field (in volts per meter).
F
Lorentz force (in newtons).
I
Current (in amperes).
j
Electric current density (in amperes per square
meter).
H
Magnetic field intensity (in amperes per meter).
k
Thermal conductivity (in watts per meter kelvin).
N
Number of turns.
P
Pressure (in pascals).
P0
Atmospheric Pressure = 101.325 kPa.
q
Electric charge density (in coulombs per cubic
meter).
R
Electrical resistance (in ohms).
Rspecific Specific gas constant (in joules per kilogram
kelvin).
Magnetic reluctance (in ampere-turns per weber).
Rm
r
Covered distance of the arc plasma (in millimeters).
T
Temperature (in kelvins).
Ambient temperature = 300 K.
To
t
Time (in seconds).
Δt
Time required for the arc plasma to move from a
point to another (in milliseconds).
Cartesian velocity components where i = 1, 2, 3.
Ui
Velocity of the arc plasma (in meters per second).
Varc
xi
Cartesian coordinates (x, y, z)
Greek Symbols
ρ
Fluid density (in kilograms per cubic meter).
α
Stefan–Boltzmann
constant
(α = 5.67057 ∗
10−8 W · m · K−4 ).
μ
Dynamic viscosity (in newton seconds per square
meter).
Magnetic permeability of free space (μ0 = 4π ×
μ0
10−7 N · A−2 ).
Magnetic permeability (in newtons per square
μm
ampere).
φ
Electrical potential (in volts).
ε
Permittivity of free space (ε ≈ 8.8541 × 10−1 F ·
m−1 ).
σ
Electrical conductivity (in siemens per meter).
Kronecker’s delta (δij = 1 if i = j and δij = 0 if i = j).
δij
0093-3813/$31.00 © 2012 IEEE
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IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
Fig. 1. Illustration of the new contactor model.
Abbreviations
ac
Alternating current.
CAD
Computer-aided design.
CV
Control volume.
dc
Direct current.
HSC
High-speed camera.
FFT
Fast Fourier transform.
I. I NTRODUCTION
T
HE OPTICAL imaging and numerical analysis are investigated in this paper which is a follow-up to the experimental work in Part I. The electrical contactor under discussion
in this paper was designed for the use in ac and dc railway
networks. The possibility for both ac and dc operations is very
much in demand for the interoperability, i.e., when the trains
go through countries with different operating system, ac, or dc.
This was accomplished using a new blowout technique combining permanent magnets and electromagnetic blowout coils. The
single-pole contactor enables switching of both extremely low
and very high loads and can also be used in several industrial
applications. The breaker contacts are separated from each
other, thus allowing an electrical potential difference between
the contacts, which leads to the establishment of arc plasma
[Part I]. The applied magnetic field forces the arc plasma to
move in a certain path or runner until it is finally divided by
splitting plates as shown in Fig. 1.
An effective electrical contactor should be able to decrease
the switching time as well as the thermal stresses of the arc
plasma on the electrodes and the splitter plates. One technique
toward achieving this goal is to elongate the arc plasma in the
divergence runners of the contactor [2]. Other methods involve
stretching of the arc plasma between splitting plates [3], [4].
Use of many splitter plates leads to a reduction of thermal
stresses inside the body of the contactor [5]. The fast blowout
of the ionized gas can be achieved by using external magnetic
field sources such as the magnets and the coils. The former
case was studied in detail by Lindmayer and Springstubbe [6],
where a simple model of two parallel ferromagnetic materials
adhered to the arc chamber. The metallic vapor and gassing
material of the electrodes decrease the temperature and thermal
stresses of the arc plasma [7]. In this paper, the arc plasma
feeds the coils with current, which means that a part of the arc
plasma energy dissipates into the coils as a magnetic energy and
thermal energy. The desired magnetic field has been generated
using the coils described in Fig. 1 and in the patent [8]. The
magnetic field accelerates the arc plasma, thus reducing the
breaking times.
As the contactor starts to switch, the bridge in the middle of
the contactor moves downward. Consequently, the current flows
between these electrodes due to the arc plasmas established
at contact points 1 and 2. The first arc moves along line 1
between electrode A1 and the bridge and then between the
electrode B1 and the bridge until it finally elongates between
B1 and B2 to continue its path to the splitter plates. It should be
noted that there is no current in the coils, when the arc is only
burning between electrodes A1/A2 and the bridge. During the
arc motion between plates B1 and B2, a current passes through
the coil 1 then the coil 2. This would induce a magnetic field
normal to the flow direction of the arc. The second arc plasma
moves along line 2, as shown in Fig. 1, and dies out as the bridge
gets zero current.
Recently, many methods have been developed to study the
movement of ionized gases. Optoelectronic devices were used
to study the movement and structure of the arc plasma inside
the divergence region of the electrical breaker [2] or inside
narrow insulating channels [4]. The root of the arc plasma in
low-voltage electrical contactors was successfully visualized
using this method [9]. Measuring the electric arc induction
using Hall-effect probes is another option to study the dynamic
behavior of the arc [5]. Similarly, HSCs are another optical diagnostic method used by many authors [10]–[12]. In the present
study, an optical imaging method has been used in addition
to the HSC to visualize the movement of the ionized gases
between the five electrodes inside the body of the contactor.
The thermal arc plasma heats the contact material after many
shots with a high repetition rate that produces a microscopic
damage of the contact surfaces. Sometimes, the contacts weld,
thus causing damage to the contactor [13]. The design of the
electrical contactor incorporates the use of two contact points.
In case that one of the contacts welds, the electrical contactor
still continues to work.
II. O PTICAL I MAGING M ETHOD
With the purpose to study the movement of the arc plasma in
the body of the contactor, 112 holes were drilled into one side of
the contactor. Fig. 2(a) shows a map of the holes and the fiberoptic heads, whereas Fig. 2(b) shows these fiber-optic heads
embedded in the body of the contactor. The light is converted
into an electrical signal using a photodetector amplifier circuit
explained and shown in Fig. 3. The illumination of the silicon
photodiode causes a current to flow through the amplifier’s
circuit. Resistance R3 prevents the photodetector amplifier’s
circuit from overload in the case of high-energy plasma arcs.
The photodiode circuit in Fig. 3 was calibrated by supplying
a fixed-amplitude light pulse to the photodiode. The output
voltage was adjusted using the variable resistance R1 to set
a level equal to the amplitude of the inlet light pulse. This
AL-AMAYREH et al.: ARC MOVEMENT INSIDE AN AC/DC CIRCUIT BREAKER—PART II
2037
Fig. 2. Map of the hole numbers and the fiber-optic heads inside the body of the contactor. (a) Shaded holes filled with fiber-optic heads. (b) Thirty-two fiber-optic
heads embedded inside the contactor.
Fig. 3. Fiber-optic head through the walls of the contactor connected to the photodiode circuit. r = 4 mm, R2 = 2 kΩ, R3 = 5 kΩ, R4 = 1 kΩ, R5 = 2 kΩ,
C2 = 100 nF, and C1 = 100 μF.
procedure was repeated for all the photodiodes. The photodiode
signals are recorded by a National Instruments data acquisition
device at a sample rate of 50 kHz. A LabVIEW program has
been developed to control the work of all the sensors and the
storage of the data. A C++ software has been developed to
postprocess the optical readings which yield the positions and
light emissions of the ionized gases. The HSC is capable of
capturing 10 000 frames/s and fixed in front of the contactor
(for more details refer to Part I).
III. R ESULTS OF THE O PTICAL M ETHODS
The optical imaging and the HSC results are shown in
Figs. 4–7 for the case 280 A ac and 3.5 kV. The curves of the
breaking current and voltage as a function of time alongside
the calculation of the arc speed for this example were discussed
in Part 1. The optical imaging results present the strength of
the signals measured by the photodiodes, and the HSC results
show the light from the arc shining through the drilled holes.
Fig. 4(b) shows that the right and left arc plasmas are ignited
near to the holes 144 and 190, respectively. The gray-scale bar
shows that the light emission ranges from black shades (no
emission) to white shades (high emission). The magnetic field
in this contactor base arises due to the magnets. The magnetic
field is applied perpendicular to the plasma field and is shown
in the simplified model [Fig. 4(a)]. The right arc plasma moves
toward the vertical runner, whereas the left arc plasma moves
out of the contactor. As the right arc plasma in Fig. 5 reaches the
beginning of the vertical runner (i.e., when the right arc appears
between the bridge and the electrode B1), the current appears
in coil 1. In addition, the arc plasma shows an oscillation in
this region. Then, the right arc plasma, which appears in Fig. 6
between the electrodes B1/B2, carries the current between these
electrodes. Consequently, the current passes between the two
coils. The crescent arc plasma in Fig. 7 shows an elongation
before reaching the splitter plates.
The previous example shows that the contactor can be used
for ac currents. Next paragraphs illustrate an example for case
dc current to show the calculation of arc speed. Later in this
paper, these results will be compared with the numerical results.
The curves of the arc current and arc voltage for this example
appear in Fig. 8 for an operating current of 750 A and voltage of
400 Vdc . The ignition occurs at the time 41 ms, and the current
appears in the first coil then in the second coil.
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IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
Fig. 4. Ignition of the arcs for case line current of 280 A ac and 3.5 kV at t = 78.1 ms. (a) Arc plasma in the contactor base. (b) Optical imaging results.
(c) HSC results.
Fig. 5. Movement of the right arc plasma from the contactor base to the vertical runner for case line current of 280-A ac and 3.5 kV at t = 82.2 ms. (a) Deflection
of the right arc. (b) Optical imaging results. (c) HSC results.
Fig. 6. Right arc plasma runs between the electrodes B1/B2 for case line current of 280 A ac and 3.5 kV at t = 82.6 ms. (a) Right arc between electrodes B1/B2.
(b) Optical imaging results. (c) HSC results.
Fig. 7. Elongation of the right arc plasma for case line current of 280 A ac and 3.5 kV at t = 82.9 ms. (a) Arc lengthening. (b) Optical imaging results. (c) HSC
results.
The signals of four photodiodes measured along the centerline of the contactor are shown in Fig. 9. It should be noted that
these results display the first arc ignition within this switching
process. Also, all curves are filtered with FFT low-pass filter to
decrease the noise. The arc speed can be calculated as
Varc =
r
Δt
(1)
where r is the covered distance by the arc plasma; in this
example, r is the distance between the two fiber-optic heads.
Δt is the shift time between the peaks of the curves that
are marked in Fig. 9. The arc speed calculation results in
Table I show an acceleration of the arc plasma along the
centerline.
The velocity of the arc plasma increases if more current is
allocated in the arc plasma and the coils, since the Lorentz force
AL-AMAYREH et al.: ARC MOVEMENT INSIDE AN AC/DC CIRCUIT BREAKER—PART II
2039
source, and i, j, k = 1, 2, 3. The values of these variables in
each equation are summarized in Table III, where Fj is the
Lorentz force j × B.
The heat radiation Qradiation defined by Karetta and
Lindmayer [16] is given as
k T 4 − To4
Qradiation = 4α
Fig. 8. Measured currents in the coils, arc plasma, and the arc voltage for
750 A/400 Vdc .
(3)
where k = 13 [m−1 ] · p · p−1
0 is the absorption coefficient. The
viscous dissipation Qdissipation is given by
∂Uj
∂Ui
2 ∂UK ∂Ui
Qdissipation = μ
+
− δij
.
(4)
∂xi
∂xj
3 ∂xK ∂xj
The resistive heating or ohmic heating is the energy spent
through the arc written as
Qohmic = j • E.
(5)
The equations governing the electric and magnetic fields are
the Maxwell’s equations which are
= − ∂B
∇×E
∂t
= j +
∇×H
Fig. 9. Example used to show the calculation of the arc plasma speed between
selected fiber-optic heads for 750 A and 400 Vdc .
=q
∇•D
TABLE I
C ALCULATION OF THE A RC P LASMA S PEED FOR C ASE L INE C URRENT
750 DC AT 400 Vdc
∂D
∂t
(Faraday’s law)
(Ampere’s law)
(Poisson’s law)
=0
∇•B
(6)
(7)
(8)
(9)
where
= εE
D
and
= μH.
B
is proportional to the current. The results for different current
loads are shown in Table II, where the velocity of the arc plasma
Varc_152,153 was measured between the two fiber-optic heads
152 and 153.
In this mathematical model, the displacement current in Am
pere’s law ∂ D/∂t
and the electric charge density q in Poisson’s
law are neglected [18]. These simplifications in Maxwell’s
equations often are considered for describing a low-frequency
phenomenon [19]. Ohm’s law can be used to calculate the
current density inside the ionized gas fluid flow
IV. M ODELING AND D ISCRETIZATION
+U
× B).
j = σ(E
The flow of ionized gases and heat transfer inside the vertical
runner of the contactor are governed by Maxwell’s equations
and the compressible Navier–Stokes equations [14]–[17], [23].
Some simplifications were considered in order to simulate the
plasma. The mathematical model does not consider the ablation
of the contact material, and the air plasma is assumed to be in a
local thermodynamic equilibrium. The governing equations can
be represented in differential form as
∂Φ
∂(ρΦ) ∂(ρUi Φ)
∂
+
=
ΓΦ
+ QΦ (2)
ζ
∂t
∂xi
∂xi
∂xi
The relation between the electrical potential φ and the elec is written as
trical field E
where ζ and Φ represent the transported quantities in each
equation, ΓΦ is a diffusion coefficient, QΦ is a distributed
= grad φ.
E
(10)
(11)
The current continuity is the divergence of the current density
div j = 0.
(12)
correlates with the magnetic
The vector magnetic potential A
as follows:
induction flux B
= curl A.
B
(13)
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IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
TABLE II
S PEED OF THE A RC P LASMA B ETWEEN THE O PTICS 152 AND 153 A LONG THE C ENTERLINE
FOR D IFFERENT DC C URRENTS AND A VOLTAGE OF 400 Vdc
TABLE III
D ESCRIPTION OF THE Q UANTITIES AND S OURCES U SED IN (2)
Fig. 10. Mathematical model. (a) Structural grid and the coordinates. [(b)–(f)] Boundary conditions used in the mathematical model.
and the magnetic vector potential
The magnetic field H
relation can be written as
= curl
curl H
1
+ B).
curl A = σ grad φ + σ(U
(14)
μo
The resistance of the arc is Rarc = h/ Sa σds, where h is
the separation distance between the electrodes B1/B2 and Sa
is the section corresponding to the conducting zone [17]. The
equation of state is given in the form
P = ρRspecific T.
(15)
The thermodynamic coefficients of thermal plasma are
very sensitive to the temperature and pressure. In this paper,
the thermodynamic and transport properties are defined as a
function of temperature and pressure and obtained from [1]
and [20].
Fig. 11. Average arc voltage drop and average currents in the coils are taken
from the experiments as input data for the numerical model.
The mathematical model described earlier has been solved
using the finite volume method. This method transforms the
partial differential equations into linear continuous equations
AL-AMAYREH et al.: ARC MOVEMENT INSIDE AN AC/DC CIRCUIT BREAKER—PART II
2041
Fig. 12. Simplified magnetic circuit. (a) Description of the magnetic circuit. (b) Magnetic field calculated from the magnetic circuit for case 750 A at 400 Vdc .
and enables to solve even complex geometries. The geometry
of the calculation domain was generated in the CAD program
ProEngineer. Fig. 11 shows the calculation domain which is
divided into about 350 000 structured hexahedral cells; each cell
represents a CV, and all the cells describe the geometry of the
contactor. The complex geometry in the base of the contactor
has not been included. The 3-D domain has been discretized
using the program ANSYS ICEM. The computational model is
divided into 22 blocks to handle the geometry. The commercial
CFD program ANSYS CFX [21] has been used to solve the system of partial differential equations with Fortran subroutines to
implement the sources. The shear stress transport k − ω-based
model was used to simulate the turbulent flow and near walls
[21], [22]. The high-resolution advection scheme is applied in
the computations.
As shown in Fig. 10, adiabatic and no-slip conditions are
assumed at the walls. Zero static pressure and the average of the
temperature are considered in the case of opening conditions,
whereas a zero electric field flux is defined at the nonmetallic
wall. Furthermore, it is assumed that the ignition position is
at the lower point between the electrodes B1/B2. A voltage
drop is given between the electrodes B1/B2 to treat the transfer
of current [23]. The arc voltage drop and currents in the coils
are taken from the experiments as input data for the numerical
model. In order to smoothen the experimental data, about
16 experimental results are averaged for a current of 750 A
dc and a voltage of 400 V. These curves are shown in Fig. 11.
The external magnetic field is applied in the z-direction and
perpendicular to the symmetry plane.
All computations involved in this study were performed by
using 16 parallel processors. To start with, the task was solved
as a steady-state calculation with zero external magnetic fields.
This steady-state case was, in turn, used as an initial condition
for the unsteady case. The computing time for the unsteady
solution was 11 h.
The external magnetic field imposed in the plasma domain is
generated by the permanent magnets and the two coils. With the
aim of generating a more homogeneous magnetic field which
is acting perpendicular to the plasma domain, the coils and
the magnets were connected with pole plates [see Fig. 12(a)].
Without operational current, a constant magnetic field from
the permanent magnets was measured with a Gauss meter to
Fig. 13. Numerical calculation of the temperature profiles along the centerline
at different times.
Fig. 14. Comparison between the numerical and experimental results of the
arc speed along the centerline for 750 A and 400 Vdc .
be 12 mT at contact points 1 and 2, as shown in Fig. 1. The
magnetic fields from the coils change with the coil current.
Fig. 12(a) shows a coil of 200 turns and a magnetic core of
mean length L = 44 mm and diameter D = 16 mm. The core
of the coil is connected to two pole plates. The distance between
the pole plates is the length of the coil core. This system can
be modeled as a simplified magnetic circuit. Assuming that the
size of the device and the operation frequency are such that
the displacement current in Maxwell’s equations is negligible,
the magnetic flux in webers can be written as
φm = Bgap Agap =
NI
.
2Rm plate + Rm coil + Rm Gap
(16)
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IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
Fig. 15. Temperature and speed contours in the contactor for a line current of 750 A and a voltage of 400 Vdc .
The magnetic reluctance Rm can be calculated from the
equation
Rm =
L
.
μm A
(17)
The materials of the plates and the core of the coils are steel.
The values of the magnetic permeability μm can be calculated
from the magnetic induction current equation
μm =
ΔB
.
ΔH
(18)
The relation between the magnetic field B and the magnetic
field intensity H for steel becomes nonlinear for H > 500 A/m
as described by the B–H curve in the manufacturer’s datasheet.
Fig. 12(b) shows the results of (16) obtained by using the
fitting of the coil current in Fig. 11. First, the magnetic field
is generated by the magnetic circuit of the first coil, and the
magnetic field from the magnetic circuit of the second coil is
delayed.
V. R ESULTS
A. Mathematical Model Verification
To verify the mathematical model, the arc voltage drop and
currents in the coils were taken from Fig. 8 as input data for
the numerical model. Fig. 13 shows the temperature profile
in the centerline of the contactor which changes with time due
to the propagation of the arc plasma and the decrease of the arc
current. Assuming that the position of the arc plasma coincides
with the peak of the temperature profile, the velocity of the
arc can be calculated from the shift of the peak temperature
position r in time. It should be noted that the amplitude of
the temperature profile decreases as the arc plasma moves
along the centerline. The comparison between the numerical
and experimental results is shown in Fig. 14, which shows
the speed of the arc plasma at different times for a current of
750 A and a voltage of 400 Vdc . The numerical results agree
well with the measurements. These results show that the arc
plasma accelerates due to the rise of the magnetic forces.
However, the acceleration or the slope of the curve decreases
with time due to the reduction of the arc current.
B. Arc Plasma Propagation
A visualization of the arc plasma propagation is made in
Fig. 15, which shows the variation of the temperature contours
at the symmetry plane. The right side of Fig. 15 shows the
velocity distribution at the midplane at different times. The
highest temperature is seen in the lower point of the vertical
runner at time 43.5 ms with a value of more than 12 500 K.
At this particular time, the external magnetic field from the
coils is very low, and the source of external magnetic field is
only from the magnets in the contactor base. The arc plasma
temperature decreases with time due to the decrease of the arc
current, stretching of the arc, and the cooling by radiant heat.
The transient response of the arc root position to the
imposed magnetic field is shown in Fig. 16. The position of
the arc plasma root is defined by the center of the highest
temperature at the surface of the runners using the following
equation:
y • T dydz
surface
.
(19)
ya = T • dydz
surface
The magnetic force from the first coil is greater, because the
current first appears in that coil. As a result, the vertical position
AL-AMAYREH et al.: ARC MOVEMENT INSIDE AN AC/DC CIRCUIT BREAKER—PART II
2043
R EFERENCES
Fig. 16. Calculated vertical position of the arc plasma root determined at
the highest temperature at cathode (electrode B2) and anode (electrode B1),
respectively.
of the arc root in the anode is higher than that of the arc root in
the cathode. Consequently, the curvature and stretching of the
arc plasma increase with time due to the unbalanced applied
magnetic fields as well as the shape of the electrode runners.
VI. C ONCLUSION
Optical imaging software has been developed to generate
50 000 frames/s to study the movements of the ionized gases inside a new electrical contactor. The optical results show that the
position of the plasma arcs inside the body of the contactor can
be controlled by using two coils and two magnets. The results
clearly indicate that the ionized gases accelerate in the vertical
runner. In addition, the velocity of the arc plasma increases with
the increase of the total current. The optical imaging results
have been compared with the results of the HSC.
Furthermore, a 3-D numerical study of an industrial electrical
contactor has been carried out. Here, the arc plasma itself feeds
two coils beside the runner with electrical current in order
to generate a magnetic pressure. This pressure moves the arc
plasma from the contactor base to the splitter plates. The arc
plasma accelerates inside the runner due to the magnetic field of
the coils. The magnetic field from the first coil is higher than the
magnetic field from the second coil, which leads to a curvature
of the arc plasma.
However, the results of the numerical simulations should be
taken with caution. Apart from the simplifications assumed in
Section IV, the numerical model has neglected the influence of
the bridge inside the contactor base which works as anode and
cathode at the same time. The simulations of the arc plasma
can be improved by studying the ablation and evaporation of
the contacts. Further experimental and numerical investigations
need to be carried out in order to examine the factors underlying
these phenomena. This would lead to a better understanding in
the future.
ACKNOWLEDGMENT
The authors would like to thank H. Weber for the technical
assistance as well as design engineers at Schaltbau GmbH,
R. Kralik and A. Ignatov, for help and advice.
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2044
Malik I. Al-Amayreh was born in Erlangen,
Germany, on October 09, 1981. He received the
B.S. degree and M.S. degree (with honors) from
the Department of Mechanical Engineering, University of Jordan, Amman, Jordan, in 2004 and
2007, respectively. He is currently working toward
the Ph.D. degree at the Institute of Fluid Mechanics (LSTM), Friedrich-Alexander University of
Erlangen–Nuremberg, Erlangen.
In 2007–2008, he was a Lecturer with the Engineering Technology College, Al-Balqa’ Applied
University, Amman, Jordan. In 2008–2010, he was a Researcher with the
LSTM, University of Erlangen–Nuremberg. 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. He was a
recipient of the Alexander Mayer scholarship.
Harald Hofmann was born in Nuremberg,
Germany, in 1968. He received the Dipl.-Ing.
degree in electrical engineering from the FriedrichAlexander University of Erlangen–Nuremberg,
Erlangen, Germany, in 2002.
In the same year, he was recruited by the Modern
Drive Technology GmbH as a Design Engineer and
became the Head of Development in 2005. Since
2008, he has been with the Institute of Electrical
Power Systems, Friedrich-Alexander University of
Erlangen–Nuremberg. 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.
Ove Nilsson was born in Tavelsjö, Sweden, in 1956. He received the B.Sc.
degree in material physics from Umeå University, Umeå, Sweden, in 1980
and the Ph.D. degree from the Department of Experimental Physics, Umeå
University, in 1986, with a thesis on 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 Postdoctoral Researcher with the University
of Würzburg, Würzburg, Germany, where he continued in the field of thermal
physics. In 1992, he joined the newly founded Bavarian Center of Applied
Energy Research, Würzburg, where he was an Administration Manager and
a Scientist until 1998. After a period as a Sales Manager for Vitec GmbH,
Würzburg, he joined Schaltbau GmbH, Munich, in 2001, where he is a Research
Engineer. The company produces contactors, snap-action switches, connectors,
and master controllers.
IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 40, NO. 8, AUGUST 2012
Christian Weindl was born in Nuremberg,
Germany, in 1965. He received the Dipl.-Ing.
degree in electrical engineering and the Dr.-Ing.
degree (cum laude) from the Friedrich-Alexander
University of Erlangen–Nuremberg, Germany, in
1993 and 1999/2000, respectively.
From 1993 to 1995, he was with the High-Voltage
Transmission and Distribution Department (Group
System Planning), Siemens AG, Erlangen, and since
1994, he has been with the Institute of Electrical
Power Systems, Friedrich-Alexander University of
Erlangen–Nuremberg. Since 2005, he has headed an international project in
the field of the artificial aging of power cables and estimation of the remaining lifetime of electrical distribution systems. His primary research interests
are harmonic stability, control of converters and FACTS equipment, and the
interactions of these devices with the surrounding network.
Dr. Weindl was a recipient of the Literature Award of ETG/VDE in 1999, and
in 2002, his Ph.D. work was a recipient of a research price by a major German
utility (E-ON Bayern AG).
Antonio R. Delgado was born in Sevilla, Spain,
on April 17, 1956. He received the Diploma (with
honors) in process technology and the Dr.-Ing. degree (1986) from the University of Duisburg–Essen,
Essen, Germany.
In 1987–1992, he was the Head of “Fluid Mechanics and Exploitation of Microgravity” with the Center of Applied Space Technology and Microgravity
(University of Bremen, Bremen, Germany), in which
he also achieved the postdoctoral lecture qualification (1993). Then, he became the Head of Predevelopment in industry (1992–1996) and got offered two chair professorships
(1994) for thermofluid dynamics (University of Stuttgart, Stuttgart, Germany)
and for fluid mechanics and process automation (Technical University Munich,
Munich, Germany). In the latter, he was a Full Professor Chair (1995–2006)
as well as the Head of the Information Technology Group, the Study Dean,
the First Pro Dean, and the Director of the Department of Food and Nutrition
Sciences. Since 2006, he has been a Full Professor with the Institute of Fluid
Mechanics (LSTM), Friedrich-Alexander University of Erlangen–Nuremberg,
Erlangen, Germany. His research interests in different areas include those that
are connected to particle technology, nucleation of nanoparticles in supercritical
gases, and the fluid mechanical transport of particulate drugs in the human body.
He has a track record of more than 120 publications in peer-reviewed journals
and books and is the holder of more than 30 patents. He is a Member of the
Editorial Board of the “Journal of Fluid Mechanics” and a Peer Reviewer in
more than ten scientific journals and cooperates with leading research groups in
the fields of fluid mechanics and critical phenomena. Twenty Ph.D. candidates
finished their thesis under his guidance. He supervises 18 Ph.D. students and
13 postdoctoral students.