Core type | shell type transformer | Spiral core type

Core type and shell-type transformer | Spiral core type

Structure of Core Type Transformer (Single Phase):

The core of this type of transformer is made of a number of rectangular (L) shaped laminated steel sheets in which the coils occupy most of the space of the core.

Only one magnetic circuit is created in the core High and low voltage welding is done on 2 opposite arms of such core The coins are placed around the core In cylindrical type, the low voltage coil is near the core and the high voltage coil is next to the low voltage i.e. on the outside.

Sandwich-type weddings are used in single-phase shell-type transformers. In many cases, high side and low side welding are not limited to one arm to reduce leakage flux.

The "L" shaped sheets are butt jointed. The coils are screwed on top of the form according to the rules and the high side and low side terminals are taken out. For further reading,

the core preparation is completed by inserting the sheets of 1 core one by one. Insulation paper is provided between both the types of coils Insulation varnish is applied to the coils and the entire core by connecting the high and low side terminals to the terminal housing as usual. 

By heating it to the prescribed heat in the heat chamber transformer insulation capacity is then made suitable for work.

The thickness of the lamination is increased at lower frequencies, such as 0.5 mm for 25hz. The thickness of the varnish insulation of the sheet is 0.0254 mm or 0.001 inches.

This time, if Nice insulation is done, the amount of eddy current decreases 

Structure and description of single-phase shell type transformer:

This type of transformer has a rectangular shape but has three arms. The arms on both sides are empty and only the middle arm is welded.

This type of core is called shell-type because the magnetic circuit covers most of the welding space. The flux produced in the middle arm is equal to the sum of the flux produced in its two arms (f / 2).

So that the magnetic flux can be divided into two equal parts to complete the circuit, the pass of the middle arm is kept equal to the sum of the two sides of the arm.

Usually, low voltage welding is done on the adjacent core and high voltage welding is done on low voltage welding. There is insulation between both types of welding Some laminated sheets of steel are shaped like “E” and “I” to form a core by arranging the “I” on one side of the “E” and then in reverse.

However, when making the core, the work is done by inserting the spiral wedding with the form in the arm in "E". Outside the core, four terminals are taken out on each side and terminal housing is attached to the core.

The insulation capacity of the transformer is increased by heating the entire core insulation varnish including the coil to the specified temperature in the heating chamber.

Cold rolled steel is used in such cores Such cores are divided into two parts Low voltage and high voltage coils are placed one after the other when winding sandwich-type in single-phase shell type.

Spiral core type: The structure of the spiral core transformer core can be called a new type Some steel ribbons or sheets are twisted in a circle with the required space in the middle High core welding is done on one side and low side welding on the other side of the core 


1. The core is relatively strong

2. Iron loss is low at a high flux density

3. Production cost is low

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