Core Type vs Shell Type Transformer: Key Differences

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

• 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 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: