Copper used in transformers for the making of windings in form of high conductivity enameled rectangular copper conductor made up of odd numbers of individual strands, Which are classified below:

Transformer Windings makes by two types of Copper Conductors :-

1. CTC – (Continuously Transposed Conductor)
2. PICC – (Paper insulated copper conductor)

Basic Introduction:

1. Continuously Transposed Conductor 

When it comes to transformer windings, the concept of a Continuously Transposed Conductor (CTC) refers to a specialized arrangement of conductor strands that can be found within the coils of a transformer. The purpose behind incorporating a CTC design is to optimize the performance of the transformer by minimizing losses.

Typically, transformer windings consist of multiple turns of conductor wire. However, in the case of a CTC arrangement, the individual strands of the conductor undergo a continuous transposition or interchange within each turn of the winding. This unique arrangement ensures that each strand spends an equal amount of time in both the inner and outer layers of the winding.

The main objective of using a CTC configuration in transformer windings is to address the challenges posed by the skin effect and proximity effect. In alternating current (AC) systems, the current tends to concentrate near the surface of the conductor due to the opposing magnetic fields generated by the changing current flow. This concentration leads to increased resistance and higher power losses.

By continually transposing the strands within each turn, the magnetic fields resulting from the alternating currents are distributed more evenly. This effectively mitigates the skin effect and proximity effect, resulting in a more uniform distribution of current across the conductor cross-section. As a result, the AC resistance is reduced, leading to minimized power losses.

Implementing CTC windings in transformers significantly improves their efficiency and reduces energy losses. The improved current distribution achieved through the use of CTC windings contributes to better voltage regulation, decreased heating, and overall enhanced performance of the transformer.

It’s important to note that the specific design and implementation of CTC windings may vary depending on factors such as the transformer’s voltage rating, power capacity, and other considerations. CTC windings are commonly utilized in high-power applications, including power generation, transmission, and distribution systems.

(CTC) is the most used for windings on Power transformers. It consists of group of enameled rectangular wires with enamel coating

which are transposed to create a type of rectangular strand as shown in photo.  

There are some odd numbers of rectangular copper strands which is covered by insulation paper layer.

Epoxy bonded CTC consists of two parallel stakes of epoxy coated enameled rectangular copper wires, They area bunched, transposed continuously at periodic intervals and insulated with the overall cover of paper. The epoxy coating remains in semi-cured condition (B stage) at time of supply which will get fully cured during drying and processing of the coil. After curing, the epoxy coating forms excellent bonding between enameled wires with very good bond strength so that the windings will become like solid beam, capable to withstand strong electro-dynamic forces created during short circuit events.

1. Paper Insulated Copper Conductors 

PICC stands for Paper-Insulated Copper Conductor. It refers to a specific type of conductor used in transformer winding construction, where copper conductors are insulated with layers of paper.

PICC windings are commonly employed in oil-filled transformers. In this design, the individual strands of copper conductor are carefully wrapped with multiple layers of insulating paper. The primary purpose of the paper insulation is to provide electrical insulation between the copper conductor and other windings or components within the transformer.

The utilization of PICC windings offers several advantages. Firstly, the paper insulation ensures effective electrical insulation, preventing direct contact between the copper conductor and other conductive elements. This insulation significantly reduces the risk of short circuits and enhances the overall safety and reliability of the transformer.

Additionally, the paper insulation used in PICC windings helps to minimize the capacitance between windings. This reduction in capacitance improves the performance and efficiency of the transformer by reducing electrical losses and improving voltage regulation.

Furthermore, the paper insulation provides mechanical support and structural integrity to the conductor within the winding. It helps maintain the proper shape and positioning of the conductor, ensuring optimal electrical performance and minimizing the chances of damage or deformation.

Moreover, the dielectric properties of the paper insulation in PICC windings enable it to withstand the high voltages present in transformers without breakdown. It also aids in dissipating the heat generated during transformer operation, contributing to the overall thermal stability and longevity of the transformer.

In summary, PICC windings, with their copper conductors and paper insulation, offer a reliable and cost-effective solution for transformer construction, especially in oil-filled transformers. They provide effective electrical insulation, mechanical support, and thermal performance, resulting in efficient and safe operation of the transformer.

It’s important to note that transformer winding designs may vary based on specific requirements and applications. While PICC windings are commonly used, different conductor insulation materials, such as enamel or synthetic substances, may also be employed based on factors like transformer design and operating conditions

(PICC) are used for winding coils of Oil filled Power & Distribution Transformers and other electrical equipment’s.

Paper insulated Copper Conductors (PICC) are the most commonly used conductors for winding coils of transformers and other electrical equipment. PICC product is available in from 1 to 4 strands integrated into one wrapped strands by insulation paper layers.