Question

Explain how laminating the core of a transformer helps to reduce eddy current losses in it. Why are the primary and secondary coils of a transformer preferably wound on the same core?

Answer 1

Hint: Laminations are transparent, making the resistance greater. Eddy currents are enclosed within each thin lamination. This decreases the whole eddy current. The maximum partition of magnetic flux and magnetic flux per turn is the same in primary and secondary.

Complete answer:
Laminations are utilized in transformers because Eddy currents are generated due to produced emf from the secondary coil of the transformer. Laminations about the transformer's core give small gaps in between, which enhances the coil's resistance. This resistance will decrease the total current and thus holds the eddy current losses.
Lamination is made to decrease the eddy current loss by enhancing the resistance of the core. The core comprises thin steel sheets, thereby having a relatively excellent resistance, each lamination being separated from others by a thin coating of varnish. The planes of these sheets are located perpendicular to the current's direction that the produced emf would set up. The planes of these sheets are organized parallel to the magnetic fields to cut beyond the eddy current ways. Thus, the laminated sheet will have an eddy current that flows within it, but the sum of unique eddy currents of all such laminations is significantly less than using a single solid iron centre.
The primary and secondary loops of a transformer are wound on the same core to decrease the flux losses and enhance the performance of the transformer. The reason for this is to obtain tight coupling among the primary and secondary on every winding. This tight coupling decreases leakage flux and inductance within primaries and secondaries, which provides less voltage drop and stronger regulation when the load is implemented to the secondary. It also guarantees that power dissipated in every set of windings is reasonably balanced.

Note: A transformer includes two electrically isolated loops. It operates on Faraday's principle of "mutual induction," An EMF is produced in the transformer's secondary coil by the magnetic flux produced by the voltages and currents running in the primary spiral winding.