∗
†
†
∗
‡
Berlin University of Technology
‡
Einsteinufer 19, D-10587 Berlin, Germany
†
ABB Switzerland Ltd.
Fabrikstrasse 3, CH-5300 Lenzburg, Switzerland
‡
ABB Industrie AG
Austrasse, CH-5300 Turgi, Switzerland
∗
Abstract — This paper describes the design, experimental investigations and the characteristics of 10 kV IGCTs for 6 kV - 7.2 kV applications. Compared to a series connection of two or three
IGCTs and inverse diodes in a three level neutral point clamped voltage source converter 10 kV IGCTs and diodes offer several attractive characteristics such as drastically increased reliability due to a substantially reduced component count, a simpler and more compact mechanical and thermal design and thus reduced converter costs. The design of 10 kV IGCTs as well as the test set up are discussed. Measurements of the blocking-, on-state- and switching behaviour are the basis for a detailed description of the device performance. The technology trade off of 10 kV IGCTs is addressed to enable an application specific optimization of the
IGCT design for low and high switching frequency applications
(e. g. railway interties and Medium Voltage Drives).
I. I NTRODUCTION
Fig. 1.
Engineering Sample of 10 kV IGCT
The Integrated Gate Commutated Thyristor (IGCT) has gained ever more importance on the market since its introduction in 1996. Low on-state voltages and fast switching transients cause minimum semiconductor losses for maximum silicon utilization in medium voltage applications [3]. The low component count in the reliable press pack and the high utilization of silicon enable the design of low cost, reliable, compact and explosion free converters. Today 4.5 kV, 5.5 kV,
6 kV and 6.5 kV IGCTs are available. IGCT based converters
Fig. 2.
Voltage Definitions of IGCTs dominate in industrial Medium Voltage Drives (MVDs) as well as Railway Interties and other Energy Management systems.
One clear technical trend of medium voltage pulse width modulated (PWM) converters is the increase of converter voltage and power. Using 5.5 kV IGCTs per switch position in a three-level neutral point clamped voltage-source converter
(3L-NPC VSC), a converter terminal voltage of V ll
, n
,
RMS =
4.16 kV can be achieved. Generally MVDs are offered in voltage classes of V ll
, n
,
RMS = 2.3 kV, 3.3 kV and 4.16 kV today. A 10 kV IGCT or a series connection of two 4.5 kV and 5.5 kV IGCTs respectively have to be applied per switch position of a 3L-NPC VSC in order to increase the converter voltage to V ll , n , RMS
= 6.0 kV - 7.2 kV. Pragmatic solutions for the IGCT series connection have been described in detail in the references [3], [4] and [5]. Therefore this paper considers the design and the characteristics of the world-first 10 kV IGCTs.
Fig. 1 shows a sample of a 68mm 10 kV IGCT.
II. M OTIVATION FOR THE 10 K V IGCT
A. Voltage requirements of IGCTs
Table I and Fig. 2 depict the voltage requirements of power semiconductors in 3L-NPC VSCs, which is currently the dominating topology in medium voltage applications (e.g. Medium
Voltage Drives, Railway interties, power quality products, etc.)
[7].
IGCTs and diodes are designed for a long term DC stability
V
DC NOM which corresponds to the nominal DC half-link voltage of a 3L-NPC VSC at 15% overvoltage of the feeding mains. (The total DC-link voltage of a 3L-NPC VSC is equivalent to 2 times the half-link voltage.) The cosmic ray withstand capability is 100 FIT (1 FIT is equivalent to one

Nominal RMS line voltage
V
TABLE I
D EVICE V OLTAGE R ATINGS IN 3L-NPC VSC ASSUMING ONE DEVICE PER SWITCH POSITION
RMS
2.3
3.3
4.16
6
6.6
6.9
7.2
(kV)
Nominal DC half-link voltage
(1.15
V
RMS ; 100 FIT; long-term DC stability)
V
DC NOM (kV)
1.9
2.7
3.4
4.9
5.4
5.6
5.9
Maximum DC half-link voltage
(1.33
V
RMS for max. SOA; short-term
DC stability)
V
DC MAX (kV)
2.2
3.1
3.9
5.6
6.2
6.5
6.8
Required semiconductor repetitive blocking voltage
V
DRM / RRM
3.3
4.5
5.5
8
9
9.5
10
(kV) failure in
10 9 voltage
V hours of operation) at the nominal device
DC NOM . The short term DC stability (about 15 s at maximum junction temperature) and the limit of the Safe
Operating Area (SOA) is achieved at maximum DC halflink voltage of a 3L-NPC VSC at 33% mains overvoltage.
The maximum repetitive forward blocking voltage of the
IGCTs and diodes
V
DRM
/
RRM is required due to dynamic overvoltages at turn-off transients caused by stray inductances of the stack and the demagnetization of the IGCT clamp circuit respectively [4].
The references [3], [4] and [5] show that a useful design of two (N=2) series-connected 4.5 kV IGCTs / diodes per switch position is possible, if a voltage derating of the converter of about 10% compared to an ideal series connection of the devices is taken into account due to imperfect voltage symmetry of series-connected devices. Table II shows the number of series-connected devices per switch position for
2.3 kV - 7.2 kV 3L-NPC VSCs if a voltage derating of
10% due to the device series-connection is assumed. A 6 kV
3L-NPC VSC could be realized using two series-connected
4.5 kV IGCTs / diodes per switch position (N=2). Two seriesconnected 5.5 kV IGCTs / diodes (N=2) or three seriesconnected 4.5 kV IGCTs / diodes (N=3) are required for
6.6 kV - 7.2 kV 3L-NPC VSCs. Alternatively 10 kV IGCTs / diodes can be applied without series connection in the voltage classes of
V ll , n , RMS
= 6.0 kV - 7.2 kV.
B. Loss considerations, number of components and reliability of 10 kV devices and a series connection of 4.5 kV and 5.5 kV devices
The depiction of the turn-off losses as a function of the on-state voltage – the so called trade-off curve or technology curve – is usually applied to evaluate and to compare the losses of power semiconductors. The technology curve is shown in
Fig. 3 for 5.5 kV IGCTs, an ideal series connection of two
5.5 kV IGCTs and 10 kV IGCTs.
Obviously the technology curves of the ideal series connection of two discrete 5.5 kV IGCTs and 10 kV IGCTs at the stationary DC-half link voltage of a 6.9 kV 3L-NPC
VSC show, that similar losses can be expected in both switch
TABLE II
N UMBER OF N SERIES CONNECTED DEVICES PER SWITCH POSITION FOR
2.3
K V - 7.2
K V MVD S ON THE BASIS OF THE 3L-NPC VSC
Nominal RMS converter line voltage
V
RMS
2.3
(kV)
3.3
4.16
6
6.6
6.9
7.2
N of
4.5 kV
IGCTs /
Diodes
3
3
2
3
1
1
-
N of
5.5 kV
IGCTs /
Diodes
2
2
-
2
-
-
1
N of
10 kV
IGCTs /
Diodes
1
1
1
1
-
-
configurations. Loss simulations in various operating points of a 6.9 kV drive applying a switching frequency of f s = 1 kHz proved that the total losses of 10 kV IGCTs / diodes and an ideal series connection of two 5.5 kV IGCTs / diodes per switch position respectively deviate only marginally in the inverter operation [6].
However, there are always additional losses in a real IGCT series connection caused by the necessary voltage balancing network. If an RC snubber is applied, there are additional snubber losses caused by the recharge of the RC snubber at turn-on and turn-off transients (e. g.
E for 4.5 kV IGCTs @ ohmic losses
P snub , R
V
DC =4500V,
I snub
,
C ≈ 0.15
E off
,
IGCT lout =2 kA) as well as of the static voltage balancing resistor if the devices blocks voltage [4].
It should be noted however, that if 10 kV and 5.5 kV devices with the same silicon area per device are applied, one
10 kV device can transfer only 50% of the losses of two series connected 5.5 kV devices if one heatsink per device is used.
Thus a 6 kV-7.2 kV 3L-NPC VSC applying 10 kV IGCTs can convert only about 50% of the power of a comparable series connection of 4.5 kV and 5.5 kV IGCT / diodes respectively if the same silicon area per device and similar

TABLE III
N UMBER OF MAIN POWER COMPONENTS AND RELIABILITY OF 6 K V-7.2
K V 3L-NPC VSC S APPLYING ONE 10 K V IGCT/ DIODE OR A SERIES
CONNECTION OF TWO DISCRETE 4.5
K V / 5.5
K V IGCT S / DIODES PER SWITCH POSITION
Components
3
10kV IGCTs/Diodes
Number of components of
∼ single
3L-NPC VSC
Number of components of two
(parallel)
3 ∼ 3L-NPC VSC
Series connection of two discrete
(4.5 kV or 5.5 kV) IGCTs/ Diodes
Number of components of single
3 ∼ 3L-NPC VSC
Main switches
•
•
•
•
IGCTs
Gate Units
Diodes
Heatsinks
RC Snubber of Main Switches
•
•
•
R
C
R stat dyn dyn
12
12
18
30
-
-
-
24
24
36
60
-
-
-
24
24
36
60
36
36
36
Clamp
•
•
•
•
•
L cl
C cl
R cl
D cl
Heatsinks
2
2
2
2
2
4
4
4
4
4
2
2
2
4
4
RC Snubber of
D cl
•
•
•
R stat
C
R dyn dyn
Total absolute number of components
-
-
-
82
-
-
-
164
Total relative number of components
FIT / FIT
∗ reference
29% 59%
44% 88%
FIT
∗ reference: FIT (Failure in Time where 1 FIT is equivalent to one failure in 10
9
4.5 kV and 5.5 kV IGCTs/diodes respectively
4
4
4
278
100%
100% hours) of a 3L-NPC VSC using a series connection of losses are assumed. Simulations showed, that a 6.9 kV 3L-
NPC VSC with a switching frequency of f s
=1 kHz applying
10 kV 91mm IGCTs / diodes can convert a power, S, of about
≤ 5.5 MVA in the inverter mode [6].
The number of the main components of the power part of one and two decoupled 6 kV-7.2 kV 3L-NPC VSCs applying discrete 10 kV devices and a series connection of two discrete
4.5 kV or 5.5 kV IGCTs / diodes per switch position is shown in Table III.
For converter powers of S ≤ 5.5 MVA, one 3L-NPC VSC with 10 kV devices has to be compared with one 3L-NPC
VSC applying a series connection of two 4.5 kV and 5.5 kV
IGCTs / diodes respectively. Assuming a useful design of both converters, the series connected 4.5 kV and 5.5kV IGCTs / diodes have a distinctly smaller silicon area per device than the 10 kV IGCTs / diodes. Obviously the 3L-NPC VSC with the series connection of two 4.5 kV and 5.5 kV IGCTs / diodes requires double the amount of semiconductors, gate units and heatsinks as well as additionally two resistors and one capacitor per device (RC snubber). If 10 kV IGCTs / diodes are applied, the total number of components of the 3L-
NPC VSC is only 29% of that of the comparable 3L-NPC
VSC with two series-connected 4.5 kV or 5.5 kV IGCTs / diodes respectively. It is clear, that the use of 10 kV IGCTs / diodes enables a remarkable reduction of both material and manufacturing costs. Additionally the maintenance concept directly profits from the simpler mechanical stack design. The reliability was calculated on the basis of the FIT-data published in reference [7].
A FIT rate of 100 was assumed for one balancing RC snubber consisting of two resistors and one capacitor. The use of 10 kV devices enables an improvement of the reliability figures by 56% due to the reduced part-count especially of gate units, gate unit supplies and semiconductors which contribute to 80% of the total FIT rate of the 3L-NPC VSC with the
IGCT series connection.
Since the losses and the thermal resistance of discrete 91mm
10 kV devices limit the maximum converter power of a 6.9 kV

Fig. 4.
One dimensional model of the 10kV IGCT
Fig. 3.
Trade-off curves for an ideal series connection of 5.5 kV IGCTs and
10 kV IGCTs (
T j =
117 ◦
C, Current density: J = 20A/cm
2
)
3L-NPC VSC to S=5.5 MVA for f s
=1 kHz, two decoupled
3L-NPC VSCs (e.g. [3]) using 10 kV devices have to be compared with one 3L-NPC VSC applying a series-connection of two 4.5 kV and 5.5 kV IGCTs / diodes respectively for converter powers of S > 5.5 MVA. In this case the use of
10 kV IGCTs leads to a reduction of the number of the main power part components by 41%. The simpler stack design and the not required RC snubbers lead to reduced material and manufacturing costs. The reduced componentcount corresponds to an improvement of the reliability by 12% and a simpler maintenance concept.
C. Potential of 10 kV IGCTs and diodes
The comparison of 3L-NPC VSCs with 10 kV IGCTs / diodes and two series connected 4.5 kV and 5.5 kV IGCTs / diodes per switch position of a 6 kV-7.2 kV 3L-NPC VSC showed, that the use of 10 kV devices enables a drastic reduction of the number of the main power part components
(by 71 % for S ≤ 5.5 MVA , by 41% for S > 5.5 MVA).
The reduced part-count also enables an essential reduction of the material and manufacturing costs. Furthermore the use of
10 kV devices substantially improves the reliability (by 56% for S ≤ 5.5 MVA , by 12% for S > 5.5 MVA). Measurements and simulations show, that the losses of 10 kV devices and a corresponding series connection of 4.5 kV and 5.5 kV devices respectively are comparable in a switching frequency range of f s
= 200 Hz – 1 kHz if an application-specific 10 kV device design is chosen. Since 10 kV devices do not require a voltage balancing network (e.g. an RC snubber or an active clamp
[3]), the simpler stack design additionally enables a simpler maintenance concept. Furthermore device selection as in the case of series connection, is not required.
III. R EQUIREMENTS AND D ESIGN OF 10 K V IGCT S
A. Requirements
It can be taken from Table I and Fig. 2, that 10 kV IGCTs are designed to feature a cosmic ray withstand capability of 100 FIT and a long term DC stability at the nominal
DC voltage of
V
DC NOM
=5.9 kV. The nominal DC voltage
V
DC NOM corresponds to a 15% overvoltage of the 7.2 kV mains. The maximum DC voltage
V
DC MAX
=6.8 kV (33% overvoltage of a 7.2 kV mains) limits the Safe Operating Area
(SOA) and characterizes the short-term dc stability (about 15 s at maximum junction temperature).
T
V j
The maximum repetitive forward blocking voltage
V
DRM
=10 kV is defined due to the dynamic overvoltages in IGCT converters. A maximum junction temperature of
=125
◦
C, small leakage currents at the blocking voltages
DC NOM
,
V
DC MAX and
V
DRM to allow a high silicon utilization.
, a wide Safe Operating
Area as well as on-state and switching losses according to the calculated technology curve are important requirements
B. Design
10 kV IGCTs require a wide neutral region to support the high blocking voltage. The device design will have to take all requirements into account, continuous DC voltage, maximum
DC voltage and repetitive blocking voltage. As a consequence, design considerations have to include breakdown voltage and its temperature dependence, leakage current after carrier lifetime engineering, cooling condition in the application and cosmic radiation withstand capability. On the other hand, it is obvious, that a minimum device thickness is mandatory to minimize the device losses.
This complicated optimization problem is somewhat simplified by the fact, that both, breakdown voltage and cosmic ray withstand capability are most stringent at lowest temperatures or temperature independent and do not depend on complicated thermal stability considerations. It therefore looks reasonable to first find a design, that fulfills these criteria with minimum thickness, and then optimize carrier lifetime engineering and maximum operating temperature for best operational performance in a second design phase, where e.g. improved thermal engineering using low temperature bonding may enter.
Cosmic ray withstand capability has become an important design criterion for power devices. Typically, a FIT rate of
2 FIT/cm
2 is considered to be acceptable. There is still some controversy regarding the model being used for estimation.

It can be taken from reference [6], that a design applying a substrate doping level of 4.2
· 10
12 cm
− 3
, which corresponds to a silicon resistivity of 1000
Ω cm , would be suited to fulfill the above mentioned criteria with a minimum n-base thickness of
700 µm . But newer estimates have led to a more conservative first design, where a 900 µm n-base thickness is required for the same FIT rate. This reflects, how incisive the cosmic ray withstand capability eventually is for high voltage devices, and how important it is to get new unified and accurate design criteria to progress along this path.
For the first 10 kV wafers, silicon of a thickness of 1050 µm and 1000
Ω cm was used. The manufacturing process of the
10 kV wafers are in line with the standard IGCT / GTO process for 4.5 kV – 6.5 kV devices. Thus also the 10 kV
IGCT features a double diffused p base layer, a heavily doped cathode emitter, a buffer layer for field stopping and a lowefficiency - transparent - anode emitter layer (Fig. 4).
Comparing the new 10 kV structure with the 4.5 kV –
6.5 kV standard devices, the main difference is a reduction of the n base doping and a considerable increase of its width. Both changes have the effect, that the standard boronaluminum double diffused p base profile becomes a more abrupt main junction if applied to the 10 kV design. This is known to be detrimental mainly to the main junction dynamic avalanche robustness. To compensate for this, samples with an especially deep aluminum profile have been made, having a main junction depth of 190 µm compared to 120 µm for the standard profile. The ratio between the n-base width and the low concentration p-base width is therefore approximately maintained. This measure is expected to be beneficial to the
SOA of the devices if switching against a high voltage. First dynamic tests up to a dynamic blocking voltage of 5.7 kV have indeed confirmed a much-improved switching performance with the deeper profile.
Fig. 6.
Waveforms of leakage current measurements the resistor
R
SC which limits the short circuit current in the case, that the DUT fails during the measurement. The value of the resistor
R
SC was chosen to be smaller than 10% of the blocking resistance of the device. The leakage current was measured with a storage oscilloscope using the shunt
R
M .
The parallel resistor
R
P enables the discharge of the DC link capacitor when the power supply is turned off. The measurements of the blocking characteristics for various IGCTs, DC link voltages and junction temperatures were automated by the use of the measurement and automation software LabVIEW.
Fig. 6 shows the corresponding waveforms.
IV. C HARACTERISTICS OF 10 K V IGCT S
A. Blocking Characteristics
The test circuit depicted in Fig. 5 was used to measure the blocking characteristics of the devices. A high voltage power supply charges the DC link capacitor to the desired blocking voltage. The device under test (DUT) is measured in series to
Fig. 7.
Forward blocking characteristic of a 68mm 10kV IGCT at T j
= 25 ◦ C
Fig. 5.
Test circuit for the investigation of the blocking characteristics
The measured forward blocking characteristic of a 68mm
10 kV IGCT is depicted in Fig. 7. The device is seen to avalanche at 25
◦
C at about 11.2 kV (lower trace). Magnifying this curve by a factor 1000 enables us to see that the 25
◦
C leakage current at 10 kV (device rating) is only 17 microamps
(upper trace).
Fig. 8 shows the blocking characteristics of four 68mm
10 kV IGCTs with different diffusion profiles and irradiation levels (e-dope only). For all devices the leakage current
I
DR is smaller than 14 mA at a device voltage of
V
AK junction temperature of
T j
=125
◦
=7 kV and a
C . Thus the blocking losses of 10 kV IGCTs are distinctly smaller than that of the static voltage balancing resistor of a comparable 4.5 kV and 5.5 kV

IGCT / diode series connection.
Fig. 8.
Forward blocking characteristic of 68mm 10 kV IGCTs at T j
= 125 ◦ C
B. On-state Characteristic
Fig. 10.
Test Circuit for the investigation of the switching behaviour of
10 kV IGCTs
T j
=85
◦
C are shown in Fig. 11. After the fast commutation of the cathode current to the gate during an interval of less than 1 µs the anode voltage of the IGCT starts to rise during a homogeneous turn off transient. When the IGCT voltage reaches the DC-link voltage, the anode current starts falling and the stray inductance of the IGCT stack causes a voltage spike due to the stray inductance of the stack.
The tail current is reached after a fall time t f =1 µs . The tail current of the IGCT decays to zero during an interval t tail
=6 µs . An instantaneous peak power of p=4.6 MW and a
Fig. 9.
On-state characteristic of a 68mm 10 kV IGCT at T j
= 125 ◦ C
T j
The on-state characteristic of a 68mm 10 kV IGCT at
=125
◦
C is depicted in Fig. 9.
The IGCT realizes an on-state voltage of 4.5 V at the maximum turn-off current of
I
TGQ = 1000 A. To calculate the on-state losses the approximation: with :
V
V
T
T
= V
T 0
+ r d
· I
A
: IGCT on − state voltage
V
T 0
: Threshold voltage ( V
T 0
= 3 .
5 V r d
: IGCT on − state resistance ( r d
)
= 1 m
Ω)
(1) can be applied (Fig. 9).
C. Turn-off Characteristic
The switching behaviour of 10 kV IGCTs was investigated in a buck test circuit in single-shot operation (Fig. 10).
V
The turn-off waveforms of a 68mm 10 kV IGCT at
DC
=5.7 kV and
I
A
=900 A at a junction temperature of
Fig. 11.
Turn-off waveform of a 68mm 10 kV IGCT
(
V
C cl
DC = 5.7 kV;
= 1 µF ,
R cl
I
A = 900 A;
= 2.3
Ω
)
T j =
85 ◦ C
,
E off = 11 Ws,
L cl = 13.6
µH ,

Fig. 13.
Technology trade off of 68mm 10 kV IGCTs
(
T j = 125
◦
C,
V
DC = 4.5 kV,
I
A = 1 kA)
TABLE IV
C ONCEPT SPECIFICATION OF 68 MM 10 K V IGCT
Characteristics
V
DRM
V
DC
I
DR
V
GR
V
TM
I
TGQ
E
OFF
R th J − C
T
J MAX
I
TSM
10 kV
6 kV
20 mA
22 V
4.5 V
1000 A
11 Ws
13 K/kW
125 ◦
C
10 kA
Conditions
T j
= 0 − 125 ◦
C for 100 FIT, 100 % DC
7 kV DC, 125
◦
C
-
-
1 kA ( r d
V
DC
= 1 m
= 6 kV
Ω
;
V
TO
I
A
= 1000 A,
V
DC
= 3.5 V)
= 6 kV
-
T = 1ms
Fig. 12.
Turn-off waveform of a 68mm 10 kV IGCT
(
V
V
DC
DC
= 2.5 kV,
= 4.7 kV,
I
T j = 85
◦ C
,
L cl
I
A
A = 800 A /
V
DC
= 880 A /
V
DC
= 13.6
µH ,
C cl
= 3.6 kV,
I
= 5.7 kV,
I
= 1 µF ,
R cl
A
A = 850 A /
= 900 A;
= 2.3
Ω
) turn off energy of
E off =11 Ws was measured. The overvoltage which occurs some microseconds after the voltage spike and reaches a maximum value of
V
AK =6.7 kV is caused by the demagnetization of the IGCT clamp (e. g. [4], [5]).
Fig. 12 shows the turn-off waveforms of the 68mm 10 kV
IGCT in a voltage range of
V
DC
= 2.5 kV - 5.7 kV at anode currents of
I of
T j
=85
◦
A
=800 A - 900 A at junction temperatures
C. Obviously the duration of the tail current substantially decreases with increasing voltage
V e. g. from t tail
=11 µs @
V
DC
=3.6 kV to t tail
=6 µs @
V
DC
DC
=5.7 kV.
D. Technology Trade-Off and Target Specification
An application-specific optimization of the IGCT design is an important factor for an optimal silicon utilization and minimal semiconductor costs in a converter. The technology trade-off in Fig. 13 shows, that there is a substantial degree of freedom in the IGCT design. A maximum silicon utilization and a minimum of semiconductor losses and costs can be achieved, if low on-state voltage IGCTs (with increased turnoff losses) are applied in low switching frequency applications
(e.g.
f s
=200 Hz–400 Hz in railway interties) and fast switching IGCTs (with low turn-off losses and increased on-state voltages) are used in high switching-frequency applications
(e. g.
f s
= 800 Hz - 1kHz in MVDs).
Table IV summarizes selected data of the concept specification of 68mm 10 kV IGCTs which enable a competitive converter design of 6.0 kV - 7.2 kV 3L-NPC VSCs without device series connection. Of course 10 kV IGCTs could be designed and manufactured in different wafer sizes e. g. 38mm, 51mm,
68mm, 91mm or even larger devices. Also other medium voltage converter topologies which currently use an IGCT or
GTO series connection per switch position will profit from
10 kV IGCTs / diodes.
V. C ONCLUSIONS
This paper describes the requirements, the semiconductor design and the characteristics of the first 10 kV IGCTs for
6 kV - 7.2 kV three level NPC Voltage Source Converters.
It is shown, that the use of 10 kV IGCTs / diodes enables a reduction of the total number of the main power components by 71% - 41% compared to a series connection of 4.5 kV or
5.5 kV devices leading to a substantial reduction of material and manufacturing costs. Furthermore the reliability of a converter applying the 10 kV IGCTs / diodes is increased by about 56% - 12%. Measurements of 10 kV IGCTs enable a consideration of blocking, on-state and switching characteristics. Finally the trade-off curve and the concept specification of 10 kV IGCTs are presented. The paper clearly shows, that
10 kV IGCTs are very attractive devices which enable an extension of the voltage range of IGCT 3L-NPC VSCs from
V ll , n , RMS
=4.16 kV to
V ll , n , RMS
= 6.0 kV - 7.2 kV without

device series connection at low costs and high reliability. In a low on-state form (2.5 V @ 1 kA), these devices will be ideally suited for the emerging markets for fast static breakers in Traction and Medium Voltage Networks.
A CKNOWLEDGMENTS
The authors would like to thank S. Kolb, Berlin University of Technology, for the support in the design of the test set up and the support of the measurements.
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Rom
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6.9 kV Medium Voltage Drives , IEEE-ISPSD 2001, Santa Fe
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Applications of IGCTs , VDE (ETG) Conference: Power Semiconductors and their Applications 2002, Bad Nauheim
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Meeting 2000, Rom
[5] A. Nagel, S. Bernet, P. K. Steimer, O. Apeldoorn, A 24 MVA Inverter using IGCT Series Connection for Medium Voltage Applications , IEEE
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Rom
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Medium Voltage Drive based on the robust IGCT and DTC technologies
IEEE IAS Annual Meeting 1999, Poenix, pp. 1505-1512