What is the shaft generator ?
It is an alternator which is driven by main propulsion propeller shaft through clutch and gearing, especially those sailing for long period at constant ship speed.
It can be used at sea when M/E is running on full speed. It is capable for load
Lloyd’s Requirements
1) Lloyd’s register would regard a shaft generator as a service main generator, if ME is intended to operate at constant speed (CPP)
2) If ME does not operate at constant speed, shaft generator would be disregarded as a service main generator, and at last 2 other independent generators would be required
Running condition
1) Full generator capacity is available within 60 ~ 100 % of normal speed
2) More suitable for shaft with CPP, (constant shaft sped and variable blade pitch)
Advantages of shaft generator
01) Saving in fuel cost is main advantage
02) Saving in LO consumption, repair and maintenance cost due to reduced main generator’s running hours
03) Reduction in noise, space and weight, capital saving by reduction of numbers and ratings of main generators
Disadvantages
01) Reduction in ship speed
02) Problems can rise to maintain electrical supply, during emergency manoeuvring astern
03) Increase in capital cost
ME driven generator
01) Fuel consumption is saved
02) Lower running and maintenance cost
03) Lower noise level in ER
04) Simple and most compact installation
Varying speed of ME, driving a fixed pitch propeller, can be converted by variable gear ratio, to provide constant Generator speed.