Three-Phase Power Measurement for Unknown Rotation and Phase Shifts
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Solution Overview
Problem
Existing three-phase power supply measurement systems face high costs due to the need for multiple sensors and cannot determine the direction of rotation accurately when it is unknown, leading to incorrect measurements.
Innovation Solution
A measurement system that includes voltage and current measurement units for three phases, with a determination unit to compute the direction of rotation and verify the installation error of current measurement units, allowing phase shift computation at low cost even when the rotation direction is unknown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are installed to measure voltage and current for all three phases, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent extracts only the necessary measurements to determine phase rotation direction and current phase shifts, eliminating the need for complete three-phase voltage and current sensing. By using selective measurement of line voltages and currents, the system achieves accurate measurement at reduced cost.
Solution Approach 2:
The measured line voltages and currents serve multiple functions: determining phase rotation direction, calculating current phase shifts, and verifying sensor installation correctness. This multi-functionality reduces the need for separate dedicated measurement circuits for each purpose.
2Power
If two wattmeters are installed to measure three-phase power, then power measurement capability is improved, but the system cannot determine direction of rotation accurately
Solution Approach 1:
The patent uses line voltage measurements as an intermediary to resolve the ambiguity in phase rotation direction. By measuring the phase relationship between line voltages and currents, the system can determine the correct rotation direction and adjust measurements accordingly, eliminating the need for trial-and-error sensor installation.
3Ease of operation
If sensors are installed without knowing the direction of rotation, then installation flexibility is improved, but measurement accuracy deteriorates
Solution Approach 1:
The patent performs preliminary determination of phase rotation direction using line voltage and current measurements before finalizing the measurement configuration. This preliminary action allows the system to automatically adjust subsequent measurements to account for the actual rotation direction, ensuring accuracy regardless of installation orientation.
Solution Approach 2:
The system uses feedback from line voltage and current measurements to determine phase rotation direction and verify sensor installation correctness. This feedback mechanism allows the system to automatically correct for installation variations and maintain measurement accuracy without requiring precise pre-installation alignment.
Data Source
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Figure 2A~2B
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AI summary
A measurement system includes: a first voltage measurement unit, which measures a first voltage as a line voltage between a first phase and a second phase of a three-phase power line configured by three phases including the first phase, the second phase, and a third phase; a first current measurement unit, which measures a first current as a current of the first phase; a third current measurement unit, which measures a third current as a current of the third phase; a determination unit, which determines a direction of rotation of the three phases on the basis of the first voltage and the first current; and a computation unit which, on the basis of at least the determination of the direction of rotation by the determination unit, computes a change in a current phase due to a load device in each of the first current, the third current, and a second current as a current of the second phase.