Toroidal Transformer Winding Method for Circulating Current Reduction
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Solution Overview
Problem
Current methods for winding low-voltage coils of toroidal transformers face challenges such as the inability to handle thick wires, labor-intensive and costly manual processes, and inefficiencies due to circulating currents in parallel windings, leading to thermal performance issues and increased size.
Innovation Solution
A novel winding strategy that involves determining the number of parallel conductors and turns per layer, winding at specific angles, cutting loops, and connecting terminal ends to form parallel conductors, which reduces circulating currents and allows for automation, using magnet wires for higher temperature ratings, and minimizing insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If thick stranded welding cables are used for low-voltage windings, then flexibility and ease of bending at core edges is improved, but the winding process becomes manual and labor-intensive, and temperature rating is limited to 105°C
Solution Approach 1:
The patent segments the thick cable into multiple thin magnet wires that are wound separately as parallel conductors. This allows automated winding machines to handle each thin wire individually while achieving the equivalent electrical function of a thick cable, thereby improving productivity without sacrificing electrical performance
Solution Approach 2:
The patent changes the temperature rating parameter from 105°C (welding cable limitation) to 220°C (magnet wire capability) by substituting the material type. This parameter change enables the use of automated winding processes and improves thermal performance while maintaining the required electrical characteristics through proper parallel conductor configuration
2Productivity
If conventional continuous winding strategy is used, then automation is achieved, but circulating currents occur in parallel windings causing increased winding losses
Solution Approach 1:
The patent applies preliminary action by carefully planning and executing the winding sequence to ensure that parallel conductors are created with equal lengths and equal numbers of turns. This preliminary configuration prevents circulating currents before they can occur, allowing automation to proceed without the harmful effects of unbalanced parallel windings
Solution Approach 2:
The patent incorporates feedback mechanisms in the form of systematic tracking and verification of turn counts and conductor lengths during the automated winding process. This ensures that each parallel conductor is wound with precise equality, preventing circulating currents while maintaining automated productivity
3Power
If thick wires are used, then current carrying capacity is improved, but flexibility is lost making it impossible to properly bend wires at core edges
Solution Approach 1:
The patent segments one thick wire into multiple thin magnet wires that are wound as parallel conductors. Each thin wire maintains flexibility for proper bending at core edges, while the parallel configuration of multiple wires achieves the equivalent current carrying capacity of the original thick wire
Solution Approach 2:
The patent applies local quality by using thin, flexible magnet wires at the core edges where bending is required, while achieving the overall current carrying capacity equivalent to thick wire through parallel configuration. Each local section has the appropriate wire thickness for its specific functional requirement
4Ease of manufacture
If more insulation is added between windings to accommodate thick wires, then ease of winding is improved, but transformer size increases and thermal performance deteriorates
Solution Approach 1:
The patent changes the wire type parameter from thick stranded cable to thin magnet wire, which fundamentally alters the insulation requirements. Thin magnet wires require minimal insulation between windings, thereby reducing the overall transformer size and improving thermal performance while maintaining ease of manufacture through automated winding capability
Data Source
AI summary
A novel winding method is described herein which eliminates the circulating currents for wound transformers. A first layer of a wire is wound about the core at a first set of angles. Next, a loop is pulled to form slack in the wire and the wire is continued to be wound at a second set of angles. The loop provides sufficient slack for the cutting and connecting described further below. The winding and loop pulling continues for s sequences to achieve the desired winding. The wire is then cut at each loop.