Inverter Voltage Metering Circuit Using Passive RC Summation
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Solution Overview
Problem
Conventional methods for regulating output voltage in voltage inverters require complex measurements involving voltage and current summation, which can be cumbersome and prone to magnetic material saturation issues.
Innovation Solution
A simplified measuring device using passive components, including capacitors and resistors, to provide a weighted sum of voltage and an image voltage of current, eliminating the need for magnetic elements and enabling efficient regulation of voltage switches in inverters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional voltage and current measurement devices are used with summing amplifier, then voltage regulation measurement is achieved, but device complexity increases and magnetic saturation issues occur
Solution Approach 1:
The patent extracts the measurement function from complex conventional devices (current transformers, summing amplifiers) and implements it using only passive RC components. The measuring device comprises simply a first resistor R1, a second capacitor C2, and a second resistor R2 connected in specific configurations, eliminating magnetic elements and complex active components while maintaining measurement capability.
Solution Approach 2:
The patent replaces the mechanical/electromagnetic measurement system (current transformers with magnetic cores) with an electronic RC circuit system. The current transformation function previously achieved through magnetic induction is replaced by RC time constant-based voltage division and differentiation, eliminating magnetic saturation issues entirely.
2Measurement precision
If conventional current transformer and summing amplifier are used, then current and voltage measurements are obtained, but magnetic saturation and non-linearity occur
Solution Approach 1:
The patent uses simple, inexpensive passive RC components (resistors and capacitors) instead of expensive and problematic magnetic measurement devices. These passive components have no magnetic saturation, no non-linearity, and maintain stable characteristics over time and temperature, providing reliable measurement without the harmful effects of magnetic materials.
3Device complexity
If passive RC components are used for measurement, then device complexity is reduced and magnetic saturation is avoided, but measurement functionality must be maintained
Solution Approach 1:
The patent carefully selects and adjusts the parameters (resistance values and capacitance values) of the RC components to achieve the desired measurement function. The time constant τ = R1×C2 is specifically designed to be much smaller than the period of the fundamental frequency, ensuring that the circuit responds appropriately to the input signals while maintaining measurement accuracy for both voltage and current components.
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
The solution allows for precise voltage regulation across capacitors, avoiding magnetic saturation and non-linearity, while being cost-effective and easily integratable into inverter devices for both low and high power applications.
Implementation Method 1
a differentiator filter (FD) mounted in parallel with the first capacitor (C1) comprising a second capacitor (C2) and a first resistor (R1) mounted in series with the second capacitor (C2)
Implementation Method 2
a differentiator filter (FD) mounted in parallel with the first capacitor (C1) comprising a second capacitor (C2) and a first resistor (R1) mounted in series with the second capacitor (C2)
Implementation Method 3
The DM measuring device further includes a second resistor R2 of value r2 mounted in parallel with the second capacitor C2 so that the first resistor R1 and the second resistor R2 form a voltage divider
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a measuring device (MD) configured to deliver a voltage corresponding to the superposition of an input voltage applied across the terminals of the measuring device (MD) and a voltage representing a current flowing through a first capacitor (C1) across whose terminals the input voltage is applied. The measuring device comprises: - a differentiator filter (DF) intended to be connected in parallel with the first capacitor (C1) and comprising a second capacitor (C2) and a first resistor (R1) connected in series with the second capacitor (C2), - a second resistor (R2) connected in parallel with the second capacitor (C2). Figure for the abstract: Fig 2