COMPONENTS OF TURBO - GENERATOR

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1STATOR FRAME
It is the heaviest component and hence a rigid frame is required due to forces and torque arising during operation. The stator frame is of welded steel single piece construction. It supports the laminated core and winding. It has radial and axial ribs having adequate strength and rigidity to minimize core vibrations and suitably designed to ensure efficient cooling. Guide bards are welded or bolted inside the stator frame over which the core is assembled. Footings are provided to support the stator foundation.

1.2 STATOR CORE
The stator core is made of laminated silicon steel sheets with high permeability and low hysterysis and eddy current losses. The sheets are suspended in the stator frame from insulated guide bars.

Stator laminations are coated with synthetic varnish; are stacked and held between sturdy steel clamping plates with non-magnetic pressing fingers which are fastened or welded to the stator frame.

In order to minimize eddy current losses of rotating magnetic flux which interacts with the core, the entire core is built of thin laminations. Each lamination layer is made of individual segments. Lamination plates are of two types, depending upon the thickness
• .65 mm thickness plates – These plates are used on both sides of a stack. Eye bars are welded on it for providing ventilation.
• 5 mm thickness plates – These are general lamination sheets which are placed within end plates for making the stack.
The segments are punched in one operation from electrical sheet steel lamination having high silicon content and are carefully deburred. The stator laminations are assembled as separate cage core without the stator frame. The segments are staggered from layer to layer so that a core of high mechanical strength and uniform permeability to magnetic flux is obtained. On the outer circumference the segments are stacked on insulated rectangular bars which hold them in position.

To obtain optimum compression and eliminate looseness during operation the laminations are hydraulically compressed and heated during the stacking procedure. To remove the heat, spaced segments are placed at intervals along the core length which divide the core into sections to provide wide radial passages for cooling air to flow.


PREPATION OF LAMINATIONS
Initially the material comes in the form of rolled sheets and then it is cut in trapezoidal form for reducing the copper losses since the material is very costly.
For high rating machines each lamination is build of 6 sectors (stampings), each of 60 cut according to the specifications. Press tools are used in the manufacture of laminations. Press tools are mainly of two types.
1. Compounding tools.
2. Blanking and slot notching tools.

Laminations are manufactured in two different ways.