Images of stator core

This is how a simple core looks like 

Copper Core

CONSTRUCTIONAL FEATURES STATOR CORE

I) Core 

Itconsists of thin laminations. Each lamination made of number of individual segments. Segments are stamped out with accurately finished die from the sheets of cold rolled high quality silicon steel.

Core after assembly

Before insulation on with varnish each segment is carefully debarred. Core is stacked with lamination segments. Segments are assembled in an interleaved manner from layer to layer for uniform permeability. Stampings are held in a position by 20 core bars having dovetail section. Insulating paper pressboards are also put between the layer of stamping to provide additional insulation and to localize short circuit.

Stampings are hydraulically compressed during the stacking procedure at different stages. Between two packets one layer of ventilating segments is provided. Steel spacers are spot welded on stamping. These spacers from ventilating ducts where the cold hydrogen from gas coolers enter the core radially inwards there by taking away the heat generated due to eddy current losses. The pressed core is held in pressed condition by means of two massive non-magnetic steel castings of press ring. The press ring is bolted to the ends of core bars. The pressure of the pressure ring is transmitted to stator core stamping through press fringes of non-magnetic steel and duralumin placed adjacent to press ring.

To avoid-heating of press ring due to end leakage flow two rings made of copper sheet are used on flux shield. The ring screens the flux by short-circuiting. To monitor the formation of hot spots resistance transducer are placed along the bottom of slots. To ensure that core losses are within limits and there are no hot spots present in the core. The core loss test is done after completion of core assembly.

2) Core Suspension

Inner part of stator

The elastic suspension of core consist of longitudinal bar type spring called core bars. Twenty core bars are welded to inner walls of stator body with help of brackets. These are made up of spring steel having a rectangular cross section and dove-tail cut at tap, similar type of dovetail is also stamped on to stamping and fit into that of core bar dovetail. Thus offering a hold point for stamping core bars have longitudinal slits which acts as inertial slots and help in damping the vibrations.

 The core bars are designed to maintain the movement of stator core with in satisfactory limits.

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