Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2002-06-20
2004-12-14
Berhane, Adolf (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S060000, C363S071000
Reexamination Certificate
active
06831845
ABSTRACT:
The invention relates to a high-voltage transformer arrangement for converting a first, relatively low direct voltage supplied by a direct-voltage source to a second, relatively high direct voltage. A high-voltage transformer arrangement of this type can be used, for example, for charging a capacitor with high capacitance over a short period of time.
Different designs are known for high-voltage transformer arrangements. The essential elements of a high-voltage transformer arrangement involve a current inverter connected to the direct current source and generally formed by an arrangement of power-electronic switches, a transformer with primary coil and secondary coil on a transformer core, a switch control for triggering the current inverter, an output rectifier that is connected to the secondary coil of the transformer and a filter connected to the output rectifier.
For nearly all applications of a high-voltage transformer arrangement of this type, the most compact transformer design possible is normally desired. The size of the transformer above all is critical for the structural volume of the high-voltage transformer arrangement. Essential elements for dimensioning a transformer designed for a high-voltage operation are the required insulation between the transformer components, namely the primary coil or coils, the transformer core and the secondary coil or coils.
When viewing a traditional transformer, for example, where a voltage of 40 kv develops against ground on the secondary side, an insulation designed for 40 kv must be provided between the location of the secondary coil where the 40 kV voltage appears and the adjacent location, which has ground or mass potential, e.g. the transformer coil that is connected to ground potential. As a result, narrow limits are set for a compact geometric dimensioning of the transformer.
It is the object of the invention to provide a high-voltage transformer arrangement for which the transformer design can be simplified considerably as compared to known high-voltage transformer arrangements.
This object is solved according to the invention for this high-voltage transformer arrangement in that the transformer core is provided with several interruption points on the magnetic path, in which insulation sections are located, and in that the transformer core sections formed by the interruptions, which are preferably controlled by potential, together with associated coils or coil sections of primary and secondary coils, form separate primary and secondary systems that are separated with respect to potential.
The creation of several “interruption points” in the transformer core creates two insulated sections of the transformer core that are completely separate with respect to potential. The term “several” means that at least two interruptions are necessary in order to create two sections that are separate with respect to potential.
The separation of the transformer core into several sections is accompanied by a complete spatial separation of the transformer into a primary system and a secondary system. This spatial separation makes it easier to insulate the area between the primary coil and the corresponding core sections or the secondary coil and the corresponding core sections. Separating the transformer according to the invention into primary and secondary systems that are insulated against each other results in an increase in the stray inductance with simultaneous tapping of the main inductance. This effect, which may not be favorable per se, can be utilized for optimizing the high-voltage transformer arrangement operation with a corresponding design for the current inverter connected to the primary system or the output rectifier connected to the secondary system.
The high-voltage transformer arrangement according to the invention can be used in power supplies with a direct-current voltage intermediate circuit.
For one special embodiment of the invention, a continuous insulator is arranged between primary system and secondary system. Starting with this basic measure, the primary systems of a plurality of transformers can subsequently be combined, in particular inside a joint housing, which then contains the transformer core sections for the individual transformers and the associated primary coils. The secondary system can be treated in the same way. The primary systems and the secondary systems can be disposed in separate housings or in a joint housing. The use of a suitable arrangement or external wiring makes it possible to control the individual sections of the transformer core or cores with respect to potential, such that the lowest maximum potential differences result between the potentials of respectively one coil and the potential of the core section assigned to this coil. The insulator disposed between the core sections must then insulate the different potentials of the core sections against each other. For this, individual core sections of the transformers can be interconnected with specific switching components (of the current inverter(s) or the output rectifier(s)), such that the interfering emission from the high-voltage transformer arrangement is minimized.
It is particularly advantageous if the energy in the inventive high-voltage transformer arrangement of a special embodiment is transmitted without intermediate storage in the transformer and based on the flux converter principle from the primary system to the secondary system. A storage choke coil with thereto-connected output capacitor is preferably connected downstream of the output rectifier. A storage choke coil can also be provided in each output branch of the output rectifier to reduce the voltage stress for the single choke coil.
Comments relating to special, advantageous embodiments of the invention are provided in the following, wherein these embodiments can be used separately or in any combination considered useful or obvious to the person skilled in the art.
The inventive concept of separating the transformer core into several sections, electrically insulating these sections and the associated creation of a primary system and a secondary system make it possible to have a variety of high-voltage transformer arrangement designs. One or several primary coils or primary coil sections can be assigned in the known manner to a transformer. In the same way, one or several secondary coils or secondary coil sections can also exist. The high-voltage transformer arrangement can be provided with one or several individual transformers.
In principle, the primary coils of several transformers can be parallel connected, wherein these primary coils are then supplied by the same direct-current source via a joint current inverter. However, the primary coils of each transformer can also be triggered separately with a separate current inverter. In addition, the primary coils can be connected in series.
The secondary coils of several transformers in the secondary system can be connected in series, wherein each secondary coil is assigned a separate output rectifier that has a separate output filter or is connected to a joint one. Also possible is a series connection of the secondary coils of the high-voltage transformer arrangement, which is then connected to a joint output rectifier.
In the following, several circuit variants for connecting the primary system or systems of a special embodiment of the high-voltage transformer arrangement are explained.
The transformer or the interconnected transformers are advantageously connected on the primary side with one terminal to the center tap of a half bridge, consisting of power-electronic switches that do not block in return direction, and with the other terminal to a capacitor.
The transformer of an alternative embodiment is connected on the primary side with each terminal to a center terminal of a
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consisting of power-electronic switches, which do not block in return direction. The power-electronic switches in particular comprise transistors. These transistors either comprise a hybrid integrated or parasitic diode, or the diode is antipa
Berhane Adolf
Kinberg Robert
Magnet-Motor Gesellschaft fur Magnetmotorische Technik mbH
Venable LLP
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