Why Are Laminations Used In Constructing The Field Core

The rotor and the stator.

Why are laminations used in constructing the field core.

Silicon steel also known as electrical steel is steel with silicon added to it. Adding silicon to steel increases its electrical resistance improves the ability of magnetic fields to penetrate it and reduces the steel s hysteresis loss. The rotor has a ring shaped iron core with slots that hold coils or windings. 1 3 field winding f1 f2 the field winding is wound on the pole core with a definite direction.

Standard laminations are described in din en 61021 in a variety of sizes and grades. Dc motors are constructed with two major parts. This induced emf causes current to flow known as eddy current. If non oriented steel was used we would need a certain amount of magnetizing force to establish flux in the core i e.

For example two e stampings plus two end closing i stampings to give an e i core forming one element of a standard shell type transformer core. The laminations of required size and shape are stamped together to get a pole which is then bolted to the yoke. A magnetic core is a piece of magnetic material with a high magnetic permeability used to confine and guide magnetic fields in electrical electromechanical and magnetic devices such as electromagnets transformers electric motors generators inductors magnetic recording heads and magnetic assemblies it is made of ferromagnetic metal such as iron or ferrimagnetic compounds such as ferrites. Laminations and core packages are used for small transformers and chokes from mains frequency to several khz.

A stator core is built up as laminations are placed side by side in order to make a complete circular or ringed layer. These lamination stampings when connected together form the required core shape. The next layer is laid offsetting each layer like a brick or cinder block wall. To be parallel to axis of the applied field.

As it requires a definite shape and size laminated construction is used. To magnetize the core. They are stamped from a pre material strip of the respective thickness and finished by a consequent annealing process to optimize the magnetic properties. The magnetizing force should be sufficient to force the domains whose axes are widely divergent from the applied field axis to come into alignment with i e.

These individual laminations are tightly butted together during the transformers construction to reduce the reluctance of the air gap at the joints producing.