Open-Phase Detection Circuit Using Negative-Phase Current
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Solution Overview
Problem
Conventional open-phase detection methods fail to accurately distinguish between a simple low output operation and an actual open phase in power conversion apparatuses, leading to potential erroneous detection.
Innovation Solution
A power conversion apparatus that generates a two-phase negative-phase current from its three-phase AC output and uses the amplitude of this current to detect an open phase, allowing for accurate differentiation between low output operations and open phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional open-phase detection methods are used, then the detection process is simple, but the detection accuracy is poor and cannot distinguish between low output operation and open phase
Solution Approach 1:
The invention changes the detection parameter from simple voltage phase difference to negative-phase current amplitude. By transforming the detection basis from voltage characteristics to current characteristics, the system can accurately identify open-phase conditions while distinguishing them from low output operations, thereby improving detection accuracy without requiring complex additional hardware
Solution Approach 2:
The invention replaces the conventional voltage-based detection mechanism with a current-based detection mechanism. By using negative-phase current amplitude as the detection parameter, the system achieves more reliable open-phase detection that is not affected by output level variations, effectively substituting one detection approach with a superior alternative
2Reliability
If voltage phase difference detection is used, then the detection method is straightforward, but it cannot accurately distinguish low output operation from open phase
Solution Approach 1:
The invention transitions from detecting voltage phase difference to detecting negative-phase current amplitude. This parameter change fundamentally improves reliability because negative-phase current amplitude inherently reflects the actual load condition, allowing the system to reliably distinguish between genuine open-phase faults and normal low output operations
Data Source
AI summary
A power conversion apparatus includes a power conversion circuit configured to convert DC power into three-phase AC power; and a control device configured to generate a two-phase negative-phase current from a three-phase AC current output from the power conversion circuit, and to detect an open phase on an output side of the power conversion circuit based on a magnitude of an amplitude of the two-phase negative-phase current. The control device may be configured to determine an occurrence of the open phase when the magnitude of the amplitude of the two-phase negative-phase current increases, and an electric current of at least one phase of the three-phase AC current decreases.