Transformer cores are generally classified into two types:
1. Shell-Type Core: This core typically has a rectangular cross-section, with each core limb having two yokes. Since the core surrounds the winding like a shell, it is called a shell-type core. Shell-type cores have fewer lamination specifications and are easy to secure. The yokes help reduce additional losses caused by leakage flux. Shell-type cores are further divided into single-phase and three-phase types. A three-phase shell-type core can be seen as comprising three independent single-phase shell-type transformers placed side by side.
2. Core-Type Core: The core limb has a stepped cylindrical cross-section, and the winding surrounds the core limb, hence it is called a core-type core, or inner-core type. This type of core has multiple lamination specifications and requires high standards for binding and clamping. However, the windings are cylindrical and easy to wind, offering good short-circuit stability. Additionally, the insulation between the winding and the core is easier to manage, making core-type cores widely used. Most transformers produced in China currently use core-type cores.
The function of the Transformer Core：
Transformers operate based on the principle of electromagnetic induction. The core is the magnetic circuit of the transformer, made by stacking silicon steel sheets with good magnetic permeability, allowing the magnetic flux to pass easily through the core to facilitate electromagnetic induction.
The core serves several essential functions:
1. Energy Conversion Medium: It works in conjunction with the winding turns to step up or step down the transformer's output voltage.
2. Structural Support: The core acts as the backbone of the transformer, housing the windings and supporting various components like leads, wooden clamps, tap changers, and other parts.
By providing these functionalities, the transformer core ensures efficient energy transfer and structural integrity of the transformer.