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Dry Type Transformer Coil Winding


Dry type transformers are an important part of electrical distribution networks, particularly in settings where safety and environmental considerations are paramount. Their coil windings play a crucial role in their operation. Let’s delve into the details of their winding types, materials, methods, and working principles.

dry type transformer coil

Winding Types

  1. Layer Winding: Used in transformers with low voltage. In this type, the winding wire is wound in layers and each layer is insulated from the other with insulation material.
  2. Disc Winding: This is more common in high voltage transformers. The winding is made up of several discs, with each disc being a group of turns. The discs are separated by insulation and are connected in series.
  3. Helical Winding: This method involves winding the coil in a helical structure. It’s often used in high current transformers. The helical design helps in better heat dissipation and reduces axial forces during short-circuit conditions.
  4. Continuous Winding: The entire winding, both primary and secondary, is wound as a single continuous conductor. This method reduces manufacturing complexity and improves voltage regulation.


  1. Conductors: Copper or aluminum are primarily used for their excellent conductivity and durability. Copper is more conductive but more expensive than aluminum.
  2. Insulation: Epoxy resins, varnish, and insulating papers are used. These materials must withstand high temperatures and electrical stresses.
  3. Core: Made from silicon steel to provide a low-resistance path for the magnetic flux.


  1. Preparation: The conductor material is prepared, usually coated for insulation.
  2. Winding: Conductors are wound on a form or core, adhering to the specific winding type design. Precise control over tension and alignment is necessary.
  3. Insulation and Impregnation: After winding, additional insulation is applied between layers or discs. The windings are often impregnated with a resin for added rigidity and heat dissipation.
  4. Testing: The finished coils are tested for electrical and mechanical integrity.

Working Principle

  1. Electromagnetic Induction: Dry-type transformers work on the principle of electromagnetic induction. The primary winding creates a magnetic field that induces a voltage in the secondary winding.
  2. Voltage Transformation: The voltage is transformed based on the ratio of turns in the primary to the secondary winding.
  3. Cooling: Since there is no liquid coolant, dry-type transformers rely on air circulation for cooling. The design of the coils and the transformer housing facilitates heat dissipation.
  4. Safety and Efficiency: The design and materials of the coil windings in dry-type transformers are focused on safety (reduced fire hazard) and efficiency (minimized losses and effective heat dissipation).

In summary, the coil winding in dry-type transformers is a sophisticated process that requires careful selection of materials, precise winding methods, and thorough testing. The design and fabrication of these coils directly influence the transformer’s performance in terms of efficiency, heat management, and operational safety.

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