Dual-Circuit Current Transformer for Common-Mode Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current transformers face challenges in accurately measuring differential-mode currents due to interference from common-mode currents, which affects the accuracy of direct current arcing detection in photovoltaic power generation systems.
Innovation Solution
A current transformer design with a magnetic core and dual primary-side windings passing through separate closed magnetic circuits, allowing for the superposition or cancellation of magnetic fluxes based on current modes, enabling independent measurement of differential and common-mode currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single primary-side winding is used in a conventional current transformer, then the structure is simple, but the common-mode current interferes with the differential-mode current measurement, reducing measurement precision
Solution Approach 1:
The magnetic core is segmented into two separate closed magnetic circuits (first and second closed magnetic circuits), each handling one primary-side winding. This segmentation isolates the magnetic flux paths, allowing differential-mode currents to be measured accurately while common-mode currents generate opposing fluxes that cancel out in the shared second magnetic core structure.
Solution Approach 2:
The first and second closed magnetic circuits are merged through the shared second magnetic core structure, which contains the first magnetic core structure. This merging allows both primary-side windings to be coupled to a common secondary-side winding, enabling simultaneous measurement of differential-mode currents while rejecting common-mode interference through flux cancellation.
2Measurement precision
If dual primary-side windings with separate closed magnetic circuits are used, then common-mode interference is suppressed and measurement accuracy is improved, but the device structure becomes more complex
Solution Approach 1:
The second magnetic core structure serves multiple functions: it forms part of both the first and second closed magnetic circuits, provides a path for both primary-side windings, and acts as the core for the secondary-side winding. This multi-functionality reduces overall structural complexity while maintaining the ability to suppress common-mode interference and measure differential-mode currents accurately.
3Ease of manufacture
If conventional current transformer design is used, then manufacturing is simple, but common-mode current affects differential-mode current output, making independent measurement difficult
Solution Approach 1:
The magnetic core is segmented into two separate closed magnetic circuits (first and second closed magnetic circuits), each handling one primary-side winding. This segmentation isolates the magnetic flux paths, allowing differential-mode currents to be measured accurately while common-mode currents generate opposing fluxes that cancel out in the shared second magnetic core structure.
Solution Approach 2:
The first and second closed magnetic circuits are merged through the shared second magnetic core structure, which contains the first magnetic core structure. This merging allows both primary-side windings to be coupled to a common secondary-side winding, enabling simultaneous measurement of differential-mode currents while rejecting common-mode interference through flux cancellation.
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
This design effectively suppresses common-mode interference, allowing for accurate collection and measurement of differential-mode currents, thereby enhancing the detection of direct current arcing in photovoltaic power generation systems.
Implementation Method 1
a first magnetic flux and a second magnetic flux are superimposed; or if the first current that flows through the first primary-side winding and the second current that flows through the second primary-side winding are common mode currents, the first magnetic flux and the second magnetic flux cancel each other out
Implementation Method 2
A change of a magnetic flux in the first magnetic core structure enables the first secondary-side winding wound around the first magnetic core structure to generate an induced current
Data Source
AI summary
A current transformer (10) includes a magnetic core, a first primary-side winding, a second primary-side winding, and a first secondary-side winding. The magnetic core includes a first magnetic core structure, a second magnetic core structure, and a third magnetic core structure. The first magnetic core structure is connected to the second magnetic core structure to constitute a first closed magnetic circuit, the first magnetic core structure is connected to the third magnetic core structure to constitute a second closed magnetic circuit, and the first magnetic core structure is a magnetic core structure common to the first closed magnetic circuit and the second closed magnetic circuit.