Correct Answer - Option 2 : thin coat of varnish
Transformer core laminations:
- The transformer core is generally made of thin strips called laminations to reduce eddy current loss.
- The thickness of the transformer core laminations is usually in the order of 0.25 mm to 0.5 mm.
- The process of lamination involves dividing the core into thin layers held together by insulating materials such as Varnish, Impregnated paper, etc.
- The thickness of silicon steel lamination is defined by varnish + silicon steel + varnish.
- Insulating material between laminations is required for electrical isolation, so as to reduce eddy current loss.
- The process of bunching all laminations is called core staggering.
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Due to lamination effective cross-section area of each layer reduces in the order of 10% and hence the effective resistance increases.
- As effective resistance increases, the eddy current losses will get decrease.
Eddy Current Losses:
In AC circuits like transformers, the iron-core losses are generated due to eddy currents flowing along the surface, the larger the path current travels the larger loss.
Eddy Current Losses are due to emf induced by a changing magnetic field. This emf causes the circulating current in the core which causes power loss.
Explanation:
- The process of lamination involves dividing the core into thin layers held together by insulating materials such as Varnish, Impregnated paper, etc.
- Due to lamination effective cross-section area of each layer reduces and hence the effective resistance increases.
- As effective resistance increases, the eddy current losses will get decrease.
- A laminated iron core has reduced eddy current losses because the laminations are insulated from each other.
