Parallel-Winding Medium-Frequency Transformer for Lower Circulating Losses
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Solution Overview
Problem
Transformers with high current and high frequency operations face challenges in maintaining low-cost construction using off-the-shelf components due to increased winding losses from circulating currents, which are exacerbated by the need for complex insulation designs that complicate manufacturing and maintenance.
Innovation Solution
A transformer design with parallel windings and series-connected impedance elements, utilizing a compact insulation system that includes low-voltage insulation between connectors and medium-voltage insulation surrounding the coil, allowing for efficient electric insulation with reduced manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If copper litz wire is used to reduce high-frequency losses, then winding losses are reduced, but the cost increases significantly and manufacturing complexity increases due to the need to parallel multiple wires
Solution Approach 1:
The patent divides the winding into multiple parallel strands (segmentation of the conductor) to reduce skin effect and proximity effect losses at high frequencies. Each strand is individually insulated and arranged in a specific pattern around the core, allowing the current to distribute more evenly across all strands, thereby reducing overall winding losses while maintaining manageable complexity through systematic arrangement.
2Power
If multiple parallel litz wires are used to handle higher currents, then current capacity increases, but circulating currents due to stray flux increase losses significantly
Solution Approach 1:
The patent arranges the parallel litz wire strands in a symmetrical configuration around the magnetic core, ensuring that each strand experiences approximately the same magnetic flux environment. This equipotential arrangement minimizes potential differences between parallel strands, thereby reducing circulating currents caused by stray flux while maintaining high current capacity through the parallel configuration.
3Reliability
If complex insulation designs are implemented to ensure reliability, then transformer reliability improves, but manufacturing complexity and difficulty increase
Solution Approach 1:
The patent employs thin film insulation layers on each litz wire strand and uses flexible insulation materials that can conform to the complex three-dimensional arrangement of windings around the core. This approach provides reliable electrical insulation between strands and turns while allowing for easier manufacturing compared to rigid insulation structures, as the flexible thin films can be applied during the winding process without requiring additional complex insulation assembly steps.
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 minimizes winding losses and maintains transformer reliability while simplifying manufacturing processes, ensuring efficient operation and cost-effectiveness for high-current, high-frequency applications.
Implementation Method 1
A transformer (141) comprises a first coil (100) surrounding a first section of the core; an electric insulation (40) surrounding the first coil (100); wherein the first coil (100) comprises a plurality of M>1 windings (101, 102); each of the plurality of M windings (101, 102) comprising i) a first termination and a second termination, ii) a conductor wound around the first portion of the core in at least one turn between the first and second termination
Implementation Method 2
the plurality of M first connectors are insulated against one another by means of a low voltage insulation (415) within the channel
Implementation Method 3
an electric insulation, in particular a medium voltage electric insulation (40), surrounding the first coil
Data Source
AI summary
A medium frequency transformer for a DC/DC converter includes: a core having an air gap and a coil surrounding a core section and having a plurality of windings; a medium voltage electric insulation, surrounding the coil each winding including a first and second termination and a conductor wound around a portion of the core in at least one turn between the first and second termination; a plurality of terminals provided outside the insulation, each connected to a different first termination by one of a plurality of connectors a channel extending from an outside of the insulation into and at least partially through said electric insulation, wherein the connectors extend through the channel and are insulated against one another by means of a low voltage insulation within the channel. The second terminations are connected to one another within or inside the insulation and connected to a second terminal outside of the insulation by a second connector.