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Posted on 01 December 2019

Power Semiconductors Take the Lead for Pulse Power Applications

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Solid State Switches from ABB for pulse power applications

Pulse power applications have for long been dominated by electron tubes like thyratrons and ignitrons. Due to the increased performance, the controllability and the long life time of power semiconductor devices, the tubes are gradually being replaced by power semiconductor assemblies The improved power semiconductor devices also enables the use of pulse power equipment in new applications, where tubes are not a viable solution.

By Adriaan Welleman and Björn Backlund, ABB Switzerland Ltd, Semiconductors

 

ABB Switzerland Ltd, Semiconductors in Lenzburg has been successfully producing power semiconductor devices for several years which are optimized for pulsed power applications. These components will replace in the near future most of the high power electron tubes like thyratrons or ignitrons in various applications. Most of the applications are for pulse modulators switching very short high energy pulses.

The speciality of these optimized semiconductor devices of ABB is the very fast switch-on capability, in micro second range, the high current rise rate, and the capability to handle high peak currents. This is often realized by combining a GCT-semiconductor device with a special designed driver unit which is optimized for fast switch-on operation, but has no switch-off capability. Therefore it can be used for capacitor discharge applications for pulse forming networks for pulse modulators. With these devices it is possible to pulse very high energy into a load, which can be a Pulse Transformer or a Klystron. Using this type of devices ABB is making complete switch assemblies which combine the IGCT (Integrated Gate Commutated Thyristor) semiconductor devices, often in series connection, an isolated clamping system, integrated power supply, optical triggering and air or water cooled heat sinks. Other devices, like thyristors or IGBTs, are also used for these applications depending on the specific application requirements. The following two examples show how BiPolar as well as BiMOS-devices have successfully been implemented in different pulsed power systems.

296 Units of this type, completely assembled with air cooled heat sinks

Power Supplies for Airport Approach Radar Systems

For several years a complete solid state switch assembly with optimized semiconductor devices was developed for the Massachusetts Institute of Technology (MIT) in Boston/USA, and these switches are in the meantime the key component for the modernization of Airport Approach Radar Systems. After long term tests, type tests and field tests, MIT recommended the ABB technology to the FAA (Federal Aviation Administration) who has in turn recommended this to an equipment maker in USA, who is the producer of the airport radar systems. In 2007 ABB Switzerland Ltd received an order for a total of several hundred complete switch assemblies, each containing 3 IGCT devices. The order is one of the largest of its kind for this application and is a clear breakthrough for the technology itself. This new technology was used to refurbish the existing radar systems at all 132 civil airports in the US and replace the relative unreliable thyratron tubes. Per airport at least two systems are used and including some spares, a total quantity of 296 switches has been supplied. The customer and end-user are both very happy with the technical and logistic performance of ABB.

The IGCT Component complete with driver unit

Advantages for the end-user

The solid state semiconductor switch has, compared with thyratrons, a clear longer life time and is practical maintenance free. Despite higher initial costs of the switch, the solid state design is cheaper during operation and already paid back after a few years. This because thyratron tubes have to be regularly adjusted and replaced which results in cost for the tube, the maintenance person and the down period of the system. It is expected that further new developments will be direct equipped with solid state switches. Because the ABB switch is built up with bipolar monolithic – one wafer per device - IGCT components, it shows a very high reliability compared with other semiconductor technologies, especially for pulsed applications. This is good for radar system users, but also other application areas like medical systems, safety systems and environmental protection systems are benefiting from this technology since the last years. ABB is actually involved in several other projects and deliveries in the application field of pulsed energy and the world wide customer base recognizes the long term collected know-how. The demand for solid state technology in pulsed power is rapidly increasing and beside the standard semiconductor component business a new market segment can be served.

Simplified circuit diagram for the assembly used for the US Airport Radars

Technology and Data

The solid state switch used for the Airport Approach Radar Systems is built-up with three IGCTs in series connection. The devices are reverse conducting, and have a switching part (with GTO structure) and a freewheeling diode monolithic integrated on one silicon wafer. The result is a practical induction free construction. The driver unit is special designed for very fast turn-on and because the application is for capacitor discharge, there is no need for turn-off. As the driver unit is direct assembled around the semiconductor device again very low induction is the result.

Wave form from the type testing with increased voltage and current

Three components each with a blocking voltage of 4500V are sandwiched between air cooled heat sinks. All three driver units are powered by one 25 kHz / 4A current source, with a HV cable through an inductive coupling. The triggering of the driver units is done by an optical signal which is transferred from a light distribution box. The safe operation area for this type of switch is in the range of 6.5kVdc, Peak Current 1.4kA, Pulse duration 2.5μs, Current Rise Rate 6kA/μs, Pulse Repetition Rate 1200Hz and ambient temperature of -10 to 50°C.

Outline of the canal with fish barrier, electrodes and the switch gear building

Power supply with BiMos devices for large fish barriers

To clean a number of rivers and canals in the US from excessive vegetation, Asian carps were released in these waters some years ago. Since the carps have no natural enemies, they could grow in size, some grow up to 1.5 m length, their numbers are beyond what was expected, and their ability to jump up to 1 meter above the surface has made them even dangerous to people. Especially for the Chicago Sanitary & Shipping Canal, a 50 m wide and 9 m deep canal that carries a quite big portion of waste water, thus enhancing the vegetation growth, the carps became a serious problem. To avoid that the carps spread to other rivers and lakes, measures had to be taken, and in support, the state of Illinois funded solutions to control the carps without poisoning or exterminating them. A US company got the assignment to build electric fish barriers that are able to repel the carps from passing certain sections of the canal. This is done by installing electrodes in the riverbed that sends electrical impulses in the water. The impulses can be sensed early by the carps and hence they avoid approaching them and turn back instead, thus staying within the boundaries set by the fish barriers.

Image 6

Technology and Data

To realize this project the US Company turned to ABB to take advantage of the experience gathered in the pulsed power field. The required power was larger than any other installed fish barrier which made it a real challenge just to define and specify the project. The final design was a switch that can deliver short rectangular pulses from a 650 kJ capacitor bank with an amplitude of 30 kA at 3.4 kV DC at a nominal frequency of 15 Hz into a 42 μH load. The pulse repetition frequency can be set between 0.5 and 100 Hz.

IGBT Modul ABB P-N - 5SNA 1200E330100. 32 pieces are used per switch

To realize the switch assembly, standard HiPak IGBT-modules were used. Due to the high voltage and high current 32 pieces of the 3.3 kV, 1.2 kA module 5SNA 1200E330100, that normally are used in traction applications, were used with 16 pieces in parallel and 2 pieces in series connection. Each fish barrier has two switches making a total of 64 IGBT-modules per barrier. The first barrier is since some time in operation and when the results have been evaluated it will be decided if this kind of electric barriers will be also installed in more rivers and canals in other parts of the country.

 

 

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