Inductive Voltage Transformer Primary Coil Capacitance
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Solution Overview
Problem
Inductive voltage converters used in low and medium voltage networks suffer from natural oscillations in the frequency range relevant to harmonics, limiting their ability to accurately measure harmonics and THD values, especially above 1.5 kHz, due to capacitors' aging and high dielectric strength requirements, making them impractical for maintaining voltage quality.
Innovation Solution
A voltage converter design where capacitance is connected in parallel to a smaller number of layers of the primary coil, with a lower dielectric strength, ensuring almost linear transmission behavior across a wide frequency range, using cast resin insulation and an exchangeable capacitance to minimize production deviations and aging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitors with high dielectric strength are used in the voltage converter, then the natural oscillations can be suppressed and transmission behavior improved, but the capacitors are exposed to high voltage causing aging and capacitance changes, which deteriorates measurement accuracy over time
Solution Approach 1:
The patent changes the operating parameters of the capacitor by connecting it to a reduced number of coil layers (e.g., only the outermost layer or a few layers), thereby reducing the voltage stress on the capacitor. This parameter change allows using capacitors with lower dielectric strength ratings, reducing aging effects while maintaining adequate oscillation suppression for measurement accuracy
Solution Approach 2:
The patent applies capacitance locally to specific coil layers rather than distributing it across all layers. By connecting the capacitor to only certain layers (local quality approach), the voltage burden on the capacitor is reduced, minimizing aging effects while still achieving sufficient suppression of natural oscillations to maintain measurement precision
2Reliability
If capacitors are connected in parallel to multiple layers of the primary coil, then natural oscillations are better suppressed, but the dielectric strength requirement increases, making the capacitors more expensive and maintenance-intensive
Solution Approach 1:
The patent changes the connection parameter by reducing the number of coil layers to which the capacitor is connected. This parameter change reduces the voltage rating requirement for the capacitor, making cheaper capacitors with lower maintenance needs suitable for the application while maintaining adequate oscillation suppression
Solution Approach 2:
The patent applies capacitance to only a partial set of coil layers rather than all layers. This partial action is sufficient to suppress the critical natural oscillations while significantly reducing the voltage stress on the capacitor, thereby lowering cost and maintenance requirements
3Measurement precision
If the voltage converter is designed for accurate harmonic measurement up to 2.5 kHz, then measurement precision is improved, but the device complexity increases due to requirements for constant transmission behavior and aging compensation
Solution Approach 1:
The patent changes the capacitor connection parameter to a reduced number of layers, which reduces aging effects and capacitance drift over time. This parameter change simplifies the need for complex compensation mechanisms while maintaining measurement precision through more stable capacitor performance
Solution Approach 2:
By reducing the voltage stress on the capacitor through connection to fewer layers, the capacitor itself provides longer stable service with minimal aging. This self-service approach maintains transmission behavior stability without requiring external compensation systems, reducing device complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design allows for accurate measurement of harmonics and THD values up to 2.5 kHz with less than 5% error, reducing maintenance needs and costs by using less expensive capacitors and allowing for easy replacement, ensuring reliable voltage quality assessment throughout the converter's lifetime.
Implementation Method 1
a capacitance (6) connected in parallel to lowermost layers of the primary coil (2), with the capacitance (6) being selected in such a way that pole-zero compensation of the first resonance of the coil arrangement of the voltage converter is achieved
Implementation Method 2
inductive voltage converters are known as voltage converters. These work on the principle of the transformer
Implementation Method 3
using cast resin insulation
Data Source
Figure 1
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Figure 3
AI summary
The invention relates to inductive voltage converters, particularly for low and medium voltages. The voltage converter (1) according to the invention comprises a primary coil (2), at least one secondary coil (3), and a coil core (4), wherein the at least one secondary coil (3) is arranged around the coil core (4) and the primary coil (2) is arranged around the at least one secondary coil (3). Furthermore, a capacitor (6) is provided in parallel with the layers of the primary coil (6), wherein the capacitor (6) is connected in parallel with the lowest layers of the primary coil (2). The number of the lowest layers is less than half the total number of layers of the primary coil (2).