A RESEARCH PRESENTATION

ON

ELECTRIC GENERATORS

PREPARED BY

BYENSITA EMMANUEL

IVQ

Kenson School of Production

Technology

23rd Jan 2012

Objectives

To have a basic understanding of

generator;

~features,

~operating procedures and

~regular maintenance practices.

TOPICS TO BE DISCUSSED

~ Introduction

~ Classification of Generators

~ Generator Systems

~ Procedure for Starting a Generator

~ Procedure for Stopping a Generator

~ Maintenance of Generators

~ Trouble Shooting of Generators

Introduction

Offshore production facilities require electrical power

for operation. This power is generated locally by

magnetic field type generators since no commercial

power services/grids are available.

Definition A generator is an integrated

electrical machine that

converts mechanical

energy into electrical

energy.

Classification of Generators

Generator according to output current;

~ DC generators and

~ AC generators

According to phase voltage;

~ Single-phase and

~ Three-phase generator

According to the fuel or source of energy used;

~ Diesel

~ Natural gas etc.

Generator Systems Engine System (prime mover)

The engine system is the source of the mechanical energy

to the generator.

It has a mechanism which burns

the input fuel to produce rotational

motion on the crankshaft.

The crankshaft is coupled to the

rotor/armature of the alternator

and transmits this rotational

motion to it.

Generator Systems

The Engine cont’d

The mechanical component engine that drives the generator

are:

Cylinder Block

Cylinder Head

Inlet valve and Exhaust valve

Piston

Piston Rings

Connecting rod

Crankshaft

Camshaft

Spark Plug

Generator Systems

The Alternator

The alternator is that part of the generator that

produces the electrical output from the mechanical

energy supplied by the engine.

Generator Systems

The alternator cont’d

Electric power is generated by rotating a coil in the

magnetic field or by rotating a magnetic field within a

stationary coil (principles of electromagnetic

induction). The value of the voltage generated

depends on;

~ The number of turns in the coil.

~ Strength of the field.

~ The speed at which the coil or

magnetic field rotates.

Generator Systems Fuel System

It consists of the fuel tank usually with sufficient storage

capacity to keep the generator operational for some time.

Common features of the fuel system include the following:

~Fuel pump which sucks fuel from

the tank to the injectors

~A vent pipe to prevent the build-up

of pressure while refilling the tank.

~Overflow connection from fuel tank

to the drain pipe to avoid spillage

of fuel on the generator set in case

of overflow.

~Fuel filter to separates foreign matter

from the fuel

Generator Systems Voltage Regulator

This component regulates the output voltage

of the generator. It keeps the produced

voltage fairly constant to prevent equipment

from damage which may result if the voltage is

too high or too low e.g.

~ electric motor-driven

pipeline pumps,

~ compressors,

~ air conditioners.

Generator Systems Cooling & Exhaust Systems

Friction of the moving parts of the generator causes its various

components to get heated up. So the cooling and ventilation

system expels the heat produced in the generator. This is

achieved by using a coolants.

Exhaust pipe allows burnt fuels to

be vented to a safe area away

from the generator.

Exhaust pipes are attached to the

engine using flexible connectors

to minimize vibrations and

prevent damage to the

generator’s exhaust system.

Generator Systems Lubricating System

A generator comprises moving parts in engine which

require lubrication to reduce wear and tear to ensure

durability and smooth operations. The generator’s

engine is lubricated by lubricating oil.

Battery System

The start function of a generator is battery operated.

The battery must be charged with a precise ‘float’

voltage. If the float voltage is very low, the battery

will remain undercharged and very high float voltage

will shorten the life of the battery.

Generator Systems Control Panel

Generated electrical power must be controlled and distributed to the

equipment through a proper power control system. A control panel is the

user interface of the generator and contains provisions for electrical outlets

and controls. Essential controls on the panel may include;

~ A switch system

~ The main circuit breaker

~ A voltmeter

~ A wattmeter

~ A running time meter

~ The ammeter

~ A frequency meter

~ A voltmeter selector switch

~ The Ammeter selector switch

~ The govern-motor speed control

Manual Procedures for Starting a

Generator

~ Perform all the necessary checks and inspection before

starting the generator.

~ Turn off all electrical loads by making sure that the

main circuit breaker on the operating unit is open

~ Start the generator prime mover (gas engine)

~ Bring the generator up to its rated speed by adjusting

the govern-motor speed control.

~ After the start-up of the generator under no load

condition, set the voltage adjusting rheostat located on

the generator control panel to the rated output voltage

~ Turn on the electrical loads by closing main circuit

breaker on the operating unit

Manual Procedures for Stopping a

Generator

~ Put the generator off-load from panel slowly

using circuit breakers.

~ Using the govern-motor speed control on the

panel, reduce the speed of the engine.

~ Allow it to run for a few minutes in idle

condition as it cools

~ Pressed the stop button to completely stop

the generator.

Maintenance of Generators

~ Check the fuel levels before starting the generator.

~ Keep generator clean from foreign material at all times

~ Check and clean air cleaners, fuel strainer cup and filter

and where necessary replace them.

~ Frequently check for grease leakage, noise, vibrations

and the tendency to overheat around bearings.

~ Check the distilled water levels in the battery.

~ Change the lubricant oil and filters following the

manufacturer's instructions.

~ Check that the generator is properly grounded at all times

to protect against electric shocks.

~ Always use a non-flammable cleaning solvent to remove

deposits of grease or oil from the generator.

Trouble Shooting a Generator

PROBLEM POSSIBLE CAUSE RECOMMENDATION

No voltage Open circuit in windings

Loss of residual magnetism in exciter

Check for continuity in windings.

Restoring residual magnetism

Low voltage High resistance connections (heating up)

Overload

Make sound connections

Reduce the load

High voltage Too high speed

Defective AVR

Check the engine

Check the AVR

Fluctuating voltage Irregular speed of engine Check engine for malfunction

Mechanical noise or

Vibration Loose or misaligned coupling

Defective bearing

Align & tighten rotor and stator

Replace bearings

Overheating Overload

Insufficient circulation

Reduce load

Improve ventilation

the

END