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Most common structures  

Laminated core transformer

Laminated core transformer is the most commonly used transformer structure. The coils are usually coiled in a plastic frame or other similar support structure. After this the coil is plated with steel alloy plates, which are attached to each other by welding or by using bolts and iron supports. Separation between primary and secondary sides is achieved with a banded plastic film or with a two-part coil holder.

The laminated core transformer is dip-varnished. The purpose of dip-varnishing is to prevent corrosion, noise caused by the plates shifting or movement of the coil threads. Finished transformers can be cased in different casing classes depending on the  use requirements.


  •     supply transformer and device transformer
  •     isolation transformer and safety voltage transformer
  •     autoconnected transformer (e.g. engine rotation speed adjustment)
  •     control voltage transformer
  •     audio transformer
  •     circuit board transformer

Ring core transformer

Ring core transformers have a core made of a steel alloy strip. The core is insulated with plastic cups or epoxy, after which the coils are coiled directly on the transformer core. Separation between the coils is usually done with a plastic film strip.  

Ring core transformers are efficient in terms of their capacity and have little loss. When connected, it receives a high switching current impulse from the supplying main. As a structure it is always more expensive than a laminated core transformer of the same power.

Ferrite transformer

Ferrite transformers have a core compressed from powders made of ferritic materials. The coils are coiled in a plastic frame. Ferrite transformers are used in high frequency (kHz – GHz) electronic applications.

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