Multiphase Circuit Power Measurement Without Neutral Conductor
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Solution Overview
Problem
Existing methods for measuring electrical quantities in multi-phase alternating current systems without a neutral conductor, such as the Aron circuit, are limited to sinusoidal voltages and symmetrical loads, and cannot accurately measure power in asymmetrical or non-sinusoidal conditions.
Innovation Solution
A method involving synchronous sampling of phase-to-phase voltages and currents in polygon or star circuits, using products of instantaneous values to calculate effective values and subsequently determining electrical quantities like power, which can handle asymmetrical loads and non-sinusoidal voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Aron circuit is used for measuring electrical quantities, then power measurement is possible in circuits with capacitive or inductive loads, but the method can only be used with sinusoidal voltages and symmetrical loads
Solution Approach 1:
The patent changes the measurement parameters from instantaneous values (which require sinusoidal conditions) to effective values (RMS values) calculated over complete periods. By integrating the product of instantaneous voltages and currents over a full period T, the method obtains accurate power measurements for any waveform shape and any load symmetry condition, thus resolving the contradiction between adaptability and measurement precision.
2Ease of operation
If phase control with leading or trailing edge is used for setting load power, then power adjustment is achieved, but power measurement with the Aron circuit becomes impossible
Solution Approach 1:
The patent ensures continuous measurement capability by integrating over complete periods regardless of phase control timing. The method continuously samples instantaneous values and integrates them over full periods, maintaining measurement continuity even when phase control disrupts the waveform symmetry, thus preserving both ease of operation and measurement precision.
Solution Approach 2:
The patent transitions from instantaneous power measurement (which fails under phase control) to periodic integration of instantaneous values. By calculating the integral of u(t)·i(t) over complete periods, the method obtains accurate effective values and power measurements that are independent of phase control timing, resolving the measurement impossibility under phase control conditions.
3Device complexity
If the Aron circuit is used for determining electrical quantities, then measurements can be carried out without a neutral conductor, but the power of individual loads can only be determined if the load is symmetrical
Solution Approach 1:
The patent segments the measurement process into individual phase measurements. By measuring the instantaneous voltage and current for each phase separately and integrating their products over complete periods, the method determines the power of individual loads independently, without requiring overall load symmetry, thus maintaining device simplicity while improving measurement precision for individual loads.
Data Source
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AI summary
Method for determining electrical quantities at loads (R1, R2, R3) in a polygon circuit or a star circuit without a neutral conductor of a multiphase AC system with P phases, wherein the polygon circuit or the star circuit is set up and wherein instantaneous values up,p+1 of line-to-line voltages up,p+1(t) and instantaneous values ip of line currents ip(t), with 1 ≤ p ≤ P and P as an element of the natural numbers, are measured by means of a measuring device by synchronous sampling of - instantaneous values up,p+1 of line-to-line voltages up,p+1(t) and - instantaneous values ip of line currents ip(t), with 1 ≤ p ≤ P and P as an element of the natural numbers, wherein for - the polygon circuit the RMS values of the load currents I1,2,...,IP-1, P, IP,1 or - the star circuit the RMS values of the load voltages U1N ,...,UPN are calculated using products hp = up,p+1 · ip ..., hP = uP,1· iP , the instantaneous values of the line-to-line voltages up,p+1 and the instantaneous values of the line currents ip.