Thursday, July 23, 2015

Generator and Alternator


By Ship Electrical Engineer Ather Rizvi's Lecture on 

Generator and Alternator 



Fuel Lever Micro Switch on the governor (red in colour) is used to stop the generator from starting and stopping it in case of emergency. One of the few reasons for the generator not getting start is this lever being in the wrong position. It is one of the majour safties of the generator and has to be checked before the starting of the generator for its working.

Lube Oil cooler is used to maintain the temperature of the lube oil.
There are 4 different types of pressure switches
  1. Lubeoil inlet low pressure Alarm.
  2. Standby lubeoil inlet auto start.
  3. Lubeoil inlet low pressure Switch.
  4. Cool F.W. inlet low pressure Alarm.
  5. Flywheel lever has two main functions.
  6. To stop the generator in case of emergency.
  7. Priming the genreator before starting or after changing the lube oil.
Drain tank is present on either side of the generator to accumulate the oil leaking from any part of the generator. It has a float switch which is responsible for intiating alarm when the tank is full.
Electrical Side of the Generator consists of Following parts:
  1. Exciter
  2. Alternator
  3. Alternator is further devided into following parts:
  4. Stator
  5. Rotor
  6. Diode
  7. Armature
  8. Heater to remove moisture and dampness from armature.
  9. The control pannel consists of following main parts
A.C.B. (Air Circuit Breaker): Light of ACB turns on when the generator gets on load.
Bus Bars: Current generated enters the bus bars in three phases and then transmitted to the starter pannel. For a 3 phase generator there are 3 bus bars labled R, S, and T. In case of motor they are labled as U,V and W.
Reverse Power Relay: R.P.R. is used to prevent the generator converting into motor. It is tested by using synchronoscope. When two generators are run in parallel synchronoscope is used to synchronise their voltage, current and most importantly phase difference. For testing R.P.R. synchronometer is used to transmit voltage generated from say generator 1 to generator 2. If R.P.R. trips means that it is working properly. R.P.R. has a reset button which can be used to reset in case of a trip.
Synchronoscope: It is used to synchronise the phase difference and voltage developed by one or more generators in parallel. It is done by lowering the r.p.m using the governor and then synchronise the supply when the needle is at 0. In case of Auto it is all done by itself.
Voltage Regulator: It is used to increase or decrese the volatage to reach the desired amount. It can only increase or decrease small amount of voltage.
Preferential Trip: It is used to supply the current to the appliances.