Main Gen & Aux

Question 1

What is the purpose of the Main Generator?

Answer 1

To convert Rotational Energy to Electrical Energy for commercial use

Question 2

What are the three required components to create electricity?

Answer 2

Conductor, magnetic field, relative motion

Question 3

Which component of our generator provides the “conductor” and the “magnetic Field”?

Answer 3

Conductor is the stator windings

Magnetic field generated in the rotor field windings

Question 4

What is the purpose of the Generator Rotor?

Answer 4

Rotating Field enables us to transfer low voltage/current DC required to produce the field safely on the rotor using collector rings

Question 5

How many poles are on the Generator Rotor? How many slots per pole?

Answer 5

4 pole rotor, 10 slots per pole

Question 6

What are the Generator Collector Rings?

Answer 6

Provide rotary connections for transmitting exictation current to the field windings

Question 7

What are teh Generator Brushes?

Answer 7

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

Question 8

What is used to transfer current from collector ring and field windings?

Answer 8

Graphite Brushes

Question 9

What is the purpose of teh Shaft Grounding Device?

Answer 9

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

Question 10

What is the Stator Core?

Answer 10

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).

Question 11

What is used to cool the stator core?

Answer 11

Hydrogen gas

Question 12

What are the stator windings (bars)?

Answer 12

Provide a conductor which when cut by magnetic field, produces an output voltage.
Hollow and cooled by Stator Water Cooling

Question 13

What is the Terminal Bushing? Cooling?

Answer 13

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)

Question 14

What are the Isolated Phase Bus Ducts?

Answer 14

used to transmit output to MPT and UAT - hollow square aluminum conductor

Question 15

Where are teh Generator Moisture Detectors? What could cause moisture?

Answer 15

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

Question 16

What is Hydrogen Cooling used for?

Answer 16

Used for cooling in the Generator - forced in generatore by double bladed single stage fans through the generator rotor and stator core

Question 17

What is used to cool the H2 Cooling Gas?

Answer 17

Hydrogen Coolers using Service Water through the tubes

Question 18

How is cooling controlled for the H2 cooling system?

Answer 18

AO TCV on outlet of Service Water from Cooler - normally set to 40C

Question 19

Why is Hydrogen used to cool the generator?

Answer 19

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

Question 20

What are disadvantages of using H2 cooling?

Answer 20

Can be explosive between 4.1% and 74.2% - ours is kept at 90%

Question 21

How do the H2 Cooler TCV’s fail

Answer 21

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

Question 22

What is the purpose of the Generator Thermal Gas Analyzer?

Answer 22

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

Question 23

What is the Hydrogen Dew Point Monitor?

Answer 23

Monitors dew point to look for moisture in Generator.

Question 24

What is the Generator Core Monitor? How does it work?

Answer 24

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

Question 25

What is the normal H2 pressure online?

Answer 25

60#

Question 26

How is generator Purging performed?

Answer 26

When online, generator is filled with H2
When taking offline, must be purged with CO2, then CO2 is purged with IA when shutdown and maintenance must be performed.

When putting back in service, IA is purged with CO2, then CO2 is purged with H2.

Question 27

What is the purpose of Bus Duct Cooling and it’s normal flow path?

Answer 27

Used to cool the Isolated Phase Bus Ducts by blowing air down the B phase and returns via the A/C Phases.
2 blowers available, normally only 1 in service when field breaker closed

Question 28

What is the power source for Iso Phase Bus Duct Cooling?

Answer 28

2A & 2AA : MCC 25-2
2B & 2BB : MCC 26-1
NO AUTO START

Question 29

What cools Bus Duct Cooling?

Answer 29

TBCCW

Question 30

What interlocks are associated with Iso bus duct cooling?

Answer 30

W/ Field Breaker C/S in NAC and bust duct fan off, will generator an alarm

Question 31

How are generator VARS controlled during a shutdown?

Answer 31

VARS are reduced to prevent reverse power trip setpoints from being changed.

Question 32

What are the temperature Limits on the ISO PHASE Bus Ducts?

Answer 32

bus temp < 105C; Duct Temp < 80C