Current Transformer Magnetic Circuit Saturation Control
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Solution Overview
Problem
Current current transformers for electronic controllers face challenges in maintaining stable secondary current output across a wide range of primary currents, from normal to overload conditions, while also managing excessive power consumption and ensuring reliable operation without auxiliary power sources.
Innovation Solution
A current transformer design featuring a closed-loop first core magnetic circuit and an independent second core magnetic circuit with fixed air gaps, where the linear core is magnetically saturated earlier than the U-shaped core, allowing for efficient magnetic flux shunting and stable secondary current output, even under high primary currents, and reducing temperature to enhance service life and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a core current transformer is used to supply power to the electronic controller, then the controller can operate reliably with sufficient power, but the secondary current output increases excessively when the primary current increases beyond normal levels
Solution Approach 1:
The magnetic circuit is segmented into two independent parts: a first magnetic circuit (U-shaped core with secondary winding) and a second magnetic circuit (linear core). This segmentation allows each circuit to handle different current ranges, with the first circuit serving normal operating conditions and the second circuit activating during overload conditions to limit excessive secondary current output.
Solution Approach 2:
The second magnetic circuit acts as an intermediary element that intervenes when primary current exceeds normal levels. By introducing this intermediate magnetic path with fixed air gaps, the patent creates a mechanism that automatically limits the magnetic flux and secondary current during overload conditions without requiring external control.
2Adaptability or versatility
If the primary current is reduced to enable ground protection at lower current levels, then the controller can provide wider protection range, but the transformer requires higher secondary current output to meet the lower primary current threshold
Solution Approach 1:
Different parts of the magnetic circuit are designed with different properties: the U-shaped core has larger cross-sectional area for handling normal current, while the linear core has smaller cross-sectional area designed to saturate at lower current levels. This local differentiation in magnetic circuit properties enables the transformer to provide wide protection range while controlling secondary current output.
3Reliability
If the secondary current output is increased to meet lower primary current thresholds, then ground protection function is enabled, but excessive energy is consumed when primary current increases
Solution Approach 1:
The magnetic circuit dynamically adapts to different operating conditions through the interaction between the two magnetic circuits. During normal operation, the first magnetic circuit handles the flux. During overload conditions, the second magnetic circuit becomes active and limits the total flux, automatically adjusting the system behavior based on the primary current level without external control.
4Device complexity
If a single magnetic circuit is used, then the structure is simple, but the transformer cannot maintain stable secondary current output across wide primary current range
Solution Approach 1:
The magnetic circuit is divided into two independent segments (U-shaped core and linear core) that work in conjunction. This segmentation allows each segment to be optimized for specific current ranges, with the linear core designed to saturate at lower currents to provide stability during overload conditions, while the U-shaped core handles normal operating currents.
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
The design achieves stable secondary current output across a wide primary current range, ensuring reliable operation of electronic controllers without additional power consumption, with the secondary current meeting demands even at low primary currents and maintaining normal operation during overloads, thus improving the transformer's performance and safety.
Implementation Method 1
electric power originates from a current flowing through a primary core-extending conductor, and an induced current in a secondary winding of the current transformer
Implementation Method 2
The area of the cross section of the linear core 13 is less than that of the cross section of the U-shaped core 12, so that the linear core 13 can be magnetically saturated earlier than the U-shaped core 12
Data Source
AI summary
A current transformer supplying a power for an electronic controller comprises two independent core magnetic circuits, wherein a first core magnetic circuit is a closed loop formed by connecting a U-shaped core and a linear core, a primary conductor extends through the closed loop, and a secondary winding for power supply is wound on the linear core; a second core magnetic circuit having an opening shape is disposed in parallel to the linear core of the first core magnetic circuit, and the open end of the second core magnetic circuit is coupled to the first core magnetic circuit through air gaps. The area of the cross section of the linear core is less than that of the cross section of the U-shaped core, so that the linear core can be magnetically saturated earlier than the U-shaped core. The centerline length of the U-shaped core is 1.5 to 4 times of that of the linear core. The current transformer of the present invention can not only normally start and work in case that a primary current is far lower than a rated current In, but also achieve the purpose of inhibiting rapid increase of an output current of the secondary windings and smoothing the output current in case that the primary current is far more than the rated current In.