Three-Phase Load Impedance Measurement Without Neutral Reference
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Solution Overview
Problem
Current three-phase power control devices cannot determine the real branch impedance of each load in star (3S) or delta (3D) configurations without an electrical neutral reference.
Innovation Solution
A three-phase power control device with current sensors, voltage taps, and a processor that synchronizes thyristor or SCR firing to calculate impedance between phases, allowing determination of real branch impedance without a neutral reference by measuring voltages and currents across phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If power control is managed without electrical neutral reference, then device complexity is reduced and ease of operation is improved, but the ability to determine real branch impedance of each load is lost
Solution Approach 1:
The patent uses equivalent impedance as an intermediary measurement that can be obtained without neutral reference, then applies mathematical transformation to derive real branch impedance. The equivalent impedance serves as a mediator between the easily measurable quantity (without neutral) and the desired quantity (real branch impedance).
Solution Approach 2:
The patent transforms the measurement parameter from direct branch impedance (which requires neutral reference) to equivalent impedance (which can be measured without neutral), then uses mathematical relationships to convert between these parameters. This parameter transformation allows measurement without the restrictive neutral reference condition.
2Adaptability or versatility
If equivalent impedance is given instead of real branch impedance, then measurement capability is maintained without neutral reference, but measurement precision and accuracy are reduced
Solution Approach 1:
The patent uses the measured equivalent impedance as feedback to calculate the real branch impedance through established mathematical relationships. The equivalent impedance measurement feeds into the calculation process, allowing derivation of the more precise real branch impedance value from the indirectly measured equivalent impedance.
Solution Approach 2:
The patent moves the measurement problem from the direct voltage-current relationship in each phase (which requires neutral) to the relationship between line-to-line voltages and currents (which doesn't require neutral), then uses mathematical transformation to recover the original phase information in a different dimensional space.
Data Source
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AI summary
In accordance with an example embodiment of the invention, a three-phase power control device is configured to synchronize firing thyristor or SCR sets in consecutive combinations of two of the three phases, to supply current to consecutive combinations of two of the three loads in a three-phase load configuration, to determine real branch impedance of each load from three combinations of two supplied loads, without need of any electrical neutral reference.