Shell Type Transformeron 24/2/2012 & Updated on Tuesday 13th of March 2018 at 04:34:42 PM
- Core Type Transformer
- Shell Type Transformer
A recent development is the spiral-core or wound-core type. Also 3-phase Shell-type transformer.
Core of Shell Type TransformerWe use ‘E’s and ‘L’s shape laminations to make the core of the shell-type transformer. We try to reduce the width of laminations as possible to reduce the effects of eddy currents.
Limb of Shell Type TransformerShell type transformer is made up of 3 limbs or legs which we can use to increase the mechanical strength of its core. Our windings are also well-protected from any mechanical damage due to the shell-type core.
We wound the HV and LV windings around the central limb which will carry the whole flux (Φ), whereas the side limbs will carry half flux (Φ/2). Hence to accommodate the flux we design the cross-section of the central limb such that it is twice the size of the side limbs. The advantage we get over here is that magnetic flux can flow through two closed magnetic paths which will decrease the core losses generated and increase the efficiency of the machine. So, we tend to get more output from shell type when compared to core type.
Winding of Shell Type TransformerWe wind both the HV and LV windings longitudinally along the core alternately. We sandwich the HV coils between two LV coils as shown in the figure below. Since both HV and LV coils are wound together in the central limb, we tend to require less number of conductor for wounding shell type. We require more insulation material as they are sandwiched between each other which could give rise to short-circuits.
The design of shell-type is a bit complex compared to core-type due to its core structure and winding nature. We need to remove a large number of windings for better maintenance which makes it very hard for repair works.
Cooling System of Shell Type TransformerWe need to implement forced air or oil cooling as heat generated during working is not easily dissipated from windings since the core surrounds it.
Applications of Shell Type TransformerWe use shell-type transformers for low voltage applications and are usually used in power circuits as well as electronic circuits. We also use them when we require reducing our expenses as they have square or rectangular cross-sections.
Advantages of Shell Type TransformerOne of the main benefits we get using shell-type is that the core gives a good support against the electromagnetic forces that can occur between the current carrying conductors during the case of a short-circuit. They also tend to have large window area which can be used for the large no. of copper conductors which will be needed when used for low-voltage applications.
Disadvantages of Shell Type TransformerWe need special fabrication facilities for the construction of a shell-type due to its complexity which will lead to increase in manufacturing and labour cost.
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