Main Gen & Aux Flashcards
What is the purpose of the Main Generator?
To convert Rotational Energy to Electrical Energy for commercial use
What are the three required components to create electricity?
Conductor, magnetic field, relative motion
Which component of our generator provides the “conductor” and the “magnetic Field”?
Conductor is the stator windings
Magnetic field generated in the rotor field windings
What is the purpose of the Generator Rotor?
Rotating Field enables us to transfer low voltage/current DC required to produce the field safely on the rotor using collector rings
How many poles are on the Generator Rotor? How many slots per pole?
4 pole rotor, 10 slots per pole
What are the Generator Collector Rings?
Provide rotary connections for transmitting exictation current to the field windings
What are teh Generator Brushes?
They ride on teh collector ring to transfer current between the collector ring and teh rotor field windings. Can replace 1 magazine in an 8 hour period
brushes made of graphite
What is used to transfer current from collector ring and field windings?
Graphite Brushes
What is the purpose of teh Shaft Grounding Device?
Prevents damage to generator and turbine bearings by removing shaft to ground voltage so voltage doesn’t go through bearing/oil film
Copper braids ride against shaft between Generator and “C” LP Turbine
What is the Stator Core?
Houses the armature windings while minimizing heat production from eddy currents.
Made up of metal punchings stacked in 2 inch segements w/ 1/2 inch spacer block between for cooling gas (hydrogen).
What is used to cool the stator core?
Hydrogen gas
What are the stator windings (bars)?
Provide a conductor which when cut by magnetic field, produces an output voltage.
Hollow and cooled by Stator Water Cooling
What is the Terminal Bushing? Cooling?
Provide a method to conduct power out of generator while maintaining seal to prevent hydrogen leakage - 3 at each end
Cooled by Bus Duct Cooling (NOT HYDROGEN)
What are the Isolated Phase Bus Ducts?
used to transmit output to MPT and UAT - hollow square aluminum conductor
Where are teh Generator Moisture Detectors? What could cause moisture?
Main Generator Casing (534) Exciter Gen Casing (534) Seal Oil Drain Enlargment (538) Alarms at 3.5 pints - local and MCR COULD BE from condensation, leak in H2 cooler, SWC Leak, oil leak
What is Hydrogen Cooling used for?
Used for cooling in the Generator - forced in generatore by double bladed single stage fans through the generator rotor and stator core
What is used to cool the H2 Cooling Gas?
Hydrogen Coolers using Service Water through the tubes
How is cooling controlled for the H2 cooling system?
AO TCV on outlet of Service Water from Cooler - normally set to 40C
Why is Hydrogen used to cool the generator?
Thermal conductivity of H2 is 7 times that of air.
Density of Hydrogent is 1/14 that of air - less windage loss (air friction)
As H2 pressure increase, density increase, heat removal increase
What are disadvantages of using H2 cooling?
Can be explosive between 4.1% and 74.2% - ours is kept at 90%
How do the H2 Cooler TCV’s fail
Fail closed on loss of air to E/P controller
Fail open on loss of air to valve or positioner
TCV controller powered by Inst Bus
What is the purpose of the Generator Thermal Gas Analyzer?
Measures thermal conductivity of gases which can be converted to H2 Purity
Alternate uses H2 fan DP can be correlated to purity
Vents to Roof when shutdown
What is the Hydrogen Dew Point Monitor?
Monitors dew point to look for moisture in Generator.
What is the Generator Core Monitor? How does it work?
Monitors generator atmosphere for evidence of particles that would be given off by insulation breakdown due to overheating
Flow is from fan D/P or H2 press vented to roof when Shutdown
Normal reading is 80%, at 50% a sample needs to be drawn
