Delta Transformer Winding Resistance Testing Using Segmented DC Currents
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Solution Overview
Problem
Measuring the resistance of Delta-connected windings in transformers is time-consuming due to the exponential balancing process, which is prolonged by low winding resistance, and existing high current testers are large, heavy, and often unable to saturate the core of large power transformers.
Innovation Solution
A method and apparatus using multiple DC current sources to apply measuring currents to both the primary and secondary sides of a Delta-connected transformer, saturating the core and allowing for faster resistance measurement by reducing the time constant of the balancing process, with the option to adjust currents based on the transformer's configuration and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If high current is used to saturate the core and reduce measurement time, then measurement speed improves, but device size and weight increase significantly
Solution Approach 1:
The patent divides the current supply function into multiple independent DC current sources (first, second, and third current sources) that can be applied to different windings separately. This segmentation allows each current source to operate at lower current levels while collectively achieving core saturation, thereby reducing the weight and size requirements compared to a single high-current source.
Solution Approach 2:
The patent combines the effects of multiple current sources applied to different windings (primary side and secondary side) to achieve core saturation. By merging the magnetic field contributions from multiple lower-current sources, the system achieves the same saturation effect as a single high-current source would provide, but with reduced device weight and complexity.
2Productivity
If measuring current is increased above core saturation level, then time constant decreases and measurement speeds up, but device complexity and size increase
Solution Approach 1:
The patent segments the measurement function into multiple independent current sources that can be controlled separately. Each current source operates at manageable current levels, and their combined effect achieves the desired measurement speed without requiring any single component to be overly complex or large.
Solution Approach 2:
The patent employs controllable DC current sources that can dynamically adjust their output based on the specific measurement requirements and transformer configuration. This dynamic control allows optimization of the measurement process for different scenarios without requiring a fixed, over-engineered device design.
3Loss of time
If series connection of primary and secondary windings is used to saturate core, then measurement time decreases, but adaptability to different transformer configurations is reduced
Solution Approach 1:
The patent segments the current application into independent sources that can be connected to different windings according to the specific transformer configuration. This allows the measurement system to adapt to various connection types (series, parallel, or other configurations) while maintaining fast measurement speeds, as each current source can be independently configured for the optimal connection scheme.
Solution Approach 2:
The patent creates a universal measurement apparatus that can handle multiple transformer configurations and connection types through its multiple independently controllable current sources. The system can be configured to work with different winding arrangements (series, parallel, or mixed) and transformer types, providing multi-functional capability that enhances adaptability while maintaining measurement efficiency.
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 approach significantly reduces measurement time, allows for testing of various transformer configurations without changing connections, and enables the use of smaller, less expensive measurement devices by achieving core saturation with lower currents, thereby improving efficiency and accuracy.
Implementation Method 1
The phenomenon of ferromagnetic saturation plays an important role in the prior art high current transformer resistance meters. The main inductance L of the transformer drastically drops when the magnetic core is saturated.
Implementation Method 2
This effect facilitates it to measure the ohmic resistance after the inductive voltage drop has decayed to zero.
Data Source
AI summary
An apparatus for measuring winding resistances of windings in a delta-connected transformer includes at least a first and a second DC current source connected each between the phase ends of a first and a second leg respectively of the primary side of the transformer and at least a third DC current source connected between two nodes of the secondary side of the transformer. Furthermore, a method for measuring a winding resistance of windings in delta-connected transformers includes the steps of applying a first and a second measuring current to each one of two corresponding legs, applying a third measuring current between two nodes of a pair of windings on the secondary side and measuring at least a winding resistance of the winding between said nodes on the secondary side of the transformer and/or the winding resistance of a leg of the primary side as soon as an inductive voltage drop in the windings substantially equals zero.