Core Type vs Shell Type Transformer: Key Differences

transformer
core type
shell type
electrical engineering
power systems

This article compares core type transformers with shell type transformers, highlighting their key differences.

Introduction:

Transformers are categorized based on several factors, including the number of phases, their construction, voltage level, and applications. Based on construction, transformers are primarily classified into:

  • Core type
  • Shell type
  • Berry type

Core Type Transformer

Core Type Transformer Core Type Transformer

  • The core can be either square or rectangular.
  • It’s typically made of silicon steel sheets (around 4% silicon). The laminations help to minimize eddy current losses.
  • The vertical portions where the coils are wound are called limbs. The top and bottom parts are known as the yoke.
  • The core material needs high permeability, ideally with a relative permeability (µr) greater than 1000.
  • Core Type Transformer have a single magnetic circuit, featuring two limbs/arms as shown in the image above. The primary and secondary windings are wound on these two limbs.

Shell Type Transformer

Shell Type Transformer Shell Type Transformer

  • Shell Type Transformer have a double magnetic circuit.
  • The core has a rectangular shape and consists of three limbs/arms and two yokes.
  • The core surrounds the windings.
  • Both the primary and secondary windings are wound on the central limb.
  • The core is constructed from very thin laminations of high-grade silicon steel to minimize eddy current and hysteresis losses within the core.

Core Type Transformer vs. Shell Type Transformer: Key Differences

The following table summarizes the main differences between core-type and shell-type transformers:

ParametersCore Type TransformerShell Type Transformer
ConstructionWinding encircles the core.Core encircles most of the winding.
Number of magnetic circuitsOnly oneTwo
Number of limbs in a core (for single phase type)TwoThree
Construction complexitySimpleDifficult
CoolingBetter, as more surface is exposed to atmosphere.Not very effective.
Repairing/MaintenanceEasy to repair as coils are easy to remove.Difficult to repair, requires removing many laminations.
ApplicationPreferred for low voltage transformer.Used for very high voltage transformer.
Type of coilsCylindrical coilsMultilayer disc type or sandwich coils
LossesMoreLess
InsulationMoreLess
Copper requirementMoreLess

Transformer Interview Questions and Answers

Prepare for transformer-related job interviews and engineering vivas with this compilation of frequently asked questions and detailed answers.

transformer
electrical engineering
interview

Electrical Circuits Interview Questions and Answers

Prepare for electrical engineering job interviews with these 10 key questions and answers covering basic circuit concepts, analysis, and components.

electrical circuit
circuit analysis
interview question

Power Supply Interview Q&A: Top 10 Questions

Ace your power supply interview with these 10 key questions and detailed answers. Learn about linear vs switching supplies, voltage regulation, and protection features.

power supply
interview question
voltage regulation