Layer Windings

Turns helically wound along the core axis, arranged in one or more successive layers. Suitable for medium-voltage applications with rectangular conductors or CTC – and for high-current duty with Cordex paperless transposed cable.

LW

Design Rationale

In layer windings, turns are helically wound one above the other along the core axis and arranged in one or more successive layers. This geometry offers considerable flexibility in conductor selection and turn count, making it the preferred solution across a wide range of medium-voltage transformer applications.

Turns may be separated by spacers to allow radial oil circulation, or wound in direct contact – in which case insulation is provided by the paper covering the conductor itself. The choice between spaced and compact construction is driven by the thermal requirements of the specific application and the voltage class of the insulation system.

For high-current applications, layer windings are manufactured using paperless transposed cables (Cordex), with spacers designed to ensure optimal insulation and effective cooling. The paperless Cordex construction eliminates the inter-strand insulation paper, reducing the winding’s radial build while maintaining full transposition – a key advantage where compactness and thermal performance must both be achieved.

Key Engineering Features

Multi-Layer Flexibility

Single or multi-layer helical construction adapts the turn count and winding height to the required voltage ratio and impedance specification, without changing the fundamental production process.

Radial Oil Cooling

Spacer-separated layers create defined radial oil ducts, enabling controlled oil flow through the winding height and predictable thermal gradient management across the entire conductor cross-section.

Conductor Versatility

Compatible with rectangular copper or aluminium conductors and continuously transposed cables (CTC), allowing the conductor cross-section and transposition to be optimised for each specific load profile.

Cordex for High Current

Paperless Cordex transposed cable eliminates inter-strand paper insulation, reducing radial build and improving cooling efficiency – the solution of choice where high current density and compactness are both required.

Technical Note

Cordex vs Standard CTC – Cordex (paperless CTC) differs from conventional continuously transposed cable in that the individual strands carry no inter-strand insulation paper. Strand-to-strand insulation is instead provided by the enamel coating of each conductor. This construction reduces the total radial build of the winding and lowers thermal resistance between strands and the cooling medium – with particular benefit in high-current, high-loss-density applications where conventional CTC would require a larger cooling duct system to achieve the same temperature rise.

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