Three Phase Synchronous Generator

Introduction

This is a 3D model of a Three Phase Synchronous Generator used in the power generation industry (large power plants).

3D Model Annotations

Three Phase Synchronous Generator

Three phase synchronous generators are used in almost all commercial power plant; the less common type is the induction generator. Generators convert the mechanical energy provided by the prime mover (steam turbine, gas turbine, water turbine etc.) into electrical energy.

Exciter

Excitation refers to the direct current (DC) supplied to the rotor windings in order to control the strength of its magnetic field. Excitation current (DC current) is supplied using either brushed or brushless excitation means; most modern generators use brushless excitation as it requires less maintenance than its brushed counterpart.

Stator Core and Windings

The stator is manufactured from laminate steel. It has milled slots along its entire length that are filled with copper conductor windings. Each winding slot is fitted with a wedge to prevent the copper windings being displaced due to the centrifugal forces created during operation. Alternating current is induced in the stator windings as the rotor’s magnetic fields intersect with the windings.

Rotor and Windings

The rotor consists of solid steel with slots milled along its entire length; the slots are filled with copper conductor windings. Direct current (DC) is supplied to the rotor windings to produce an electromagnetic field around the rotor. As the rotor rotates, the north and south of its magnetic fields will induce alternating current (AC) flow in the stator windings.

Bearings

Bearings support the weight of the shaft when the generator is idle and in operation. Small units may use anti-friction roller bearings, but larger units use plain/sliding bearings. Where plain bearings are used, it is essential the lubricating oil pressure is maintained when the generator is in operation. A reduction in lubrication oil pressure will lead to damage of the bearings and shaft.

Cooling System

Cooling is achieved by air, hydrogen, or water. Small generators can be air cooled, larger units are often hydrogen cooled, whilst very large units maybe water cooled.

Frame

The frame houses the stator, rotor, bearings and cooling channels used by the generator. It provides the structural strength needed to mount all components and is designed to absorb vibration.

Bushings

Bushings are used to pass electrical current through the enclosure of the generator without raising the electrical potential of the generator casing. Bushings usually consist of an aluminium or copper central conductor and a porcelain insulator.

Retaining Ring

Retaining rings place residual compression stress upon the rotor windings; this counteracts the centrifugal forces the windings are subjected to when the generator is in operation.

Cooling Fans

Air is drawn through the generator casing using single stage axial fans; it removes waste heat from the generator casing.

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