Electricity: power supply or regulation systems – Including a transformer or an inductor – Potential transformer
Patent
1997-09-05
1999-03-16
Wong, Peter S.
Electricity: power supply or regulation systems
Including a transformer or an inductor
Potential transformer
324126, H01F 3824, G01R 114
Patent
active
058835083
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a voltage transformer with a voltage divider for measuring the voltage in medium high voltage and high voltage installations, having a combined arrangement of an ohmic divider resistor and means for compensating ambient electromagnetic effects.
Such voltage transformers with voltage dividers are known from DE 29 30 672 C2 or DE-OS 29 30 767. The known voltage divider consists of lens-shaped resistor elements which each have a central opening. With their central openings the resistor elements have been placed on a common threaded bolt, by means of which they are maintained together and fastened. Capacitively effective electrodes are also fastened on the same threaded bolt by being clamped between the lens-shaped resistor elements. The electrodes keep interferences by capacitive influences of the surroundings away from the voltage divider. The known device is expensive to produce, since the individual resistor elements must be individually produced and assembled. This applies even more so in connection with the coating of the resistor elements by means of a thick film resistance paste suggested by the mentioned references. This coating must be applied individually to each resistor element.
SUMMARY OF THE INVENTION
It is the object of the invention to disclose a voltage transformer which is insensitive to ambient electromagnetic influences, is simply constructed and can be produced with small outlay.
This object is attained in accordance with the invention in that a divider resistor is made of one piece with a measuring resistor and with taps and is sputtered in the form of a metal material on a supporting material or is produced in accordance with thick film technology, wherein at least one tap is connected with at least one compensation element. In connection with the subject of the invention, the voltage divider can be advantageously produced in a simple way in a single process step by coating a supporting material, wherein the measuring resistor and the taps for the compensation elements are simultaneously produced. It is merely necessary to connect the compensation elements with the said taps to form the voltage transformer.
A voltage transformer in accordance with the invention can be considerably smaller and lighter, and can be produced with less effort. In addition, because of its small size and the production methods it is possible to integrate further additional components, circuit connections and passive components in the course of the thick film process. When using the voltage transformer in switchgear, it is possible to design the entire switch cell smaller and more compact.
A further important advantage is the low-output design, because of which an effective cooperation with modern versions of information processing, for example in switchgear technology, is assured. Furthermore, with the technically uniform embodiment of the high and low voltage resistor of the divider, a uniform coefficient of temperature expansion and a uniform temperature are obtained, with the advantage of a very small temperature dependence of the divider ratio.
In connection with a particularly simple production a preferred embodiment is recommended, wherein the divider resistor is arranged on a flat supporting plate and the taps at the edges of the supporting plate. Other components can be connected particularly easily to the lateral taps.
In order to keep interferences by ambient capacitive effects particularly effectively away from the voltage divider, it is recommended to employ electrodes as the compensation elements which, in respect to their capacitance, are of such a size that accidental capacitive effects and those based on the environment can be defined or compensated to a large extent by a definite electrode design. The capacitive effects on the transmission behavior are compensated by dimensioning a capacitance at the low voltage resistor so that it has a defined relationship with the capacitance at the high voltage resistor.
In this way the transmission
REFERENCES:
patent: 5220495 (1993-06-01), Zulaski
patent: 5241260 (1993-08-01), Beland
Ermisch Jochen
Georgi Axel
Duromer Kunststoffverarbeitungs-GmbH
Striker Michael J.
Vu Bao Q.
Wong Peter S.
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