DC Power

Question 1

What are the power supplies to vital 125 vdc buses?

Answer 1

• Bus 1 (SD11) =480vac bus F (batt chgr 1-1)
• Bus 2 (SD12) =480vac bus G (batt chgr 1-2)
• Bus 3 (SD13) =480vac bus H (batt chgr 1-32)

Question 2

What are the power supplies to backup battery chargers and what busses can they supply?

Answer 2

• Batt chgr 1-21 (480 vac H) supplies bus 1 or 2
• Batt chgr 1-31 (480 vac F) supplies bus 3

Question 3

What is design basis for vital 125 vdc

Answer 3

Provide necessary dc loads from vital batteries for 2 hours

Question 4

When preparing to place SD 11 on its backup battery charger (BTC), what will you do first…..

Place b/u BTC in service

Remove norm BTC from service

Why?

Answer 4

remove Normal BTC from service

philosophy for battery chargers is break before make, do not align two battery chargers at the same time to same bus/ battery.

Question 5

What is the purpose of the curb key interlocks? (what does it prevent)

How does it do this?

Answer 5

prevents lining up the swing battery charger (BTC 1-21) to both SD-11 and SD-12 at same time

• supply breakers have ONE key
• bkr can only be closed if the key is inserted
• key will not be released unless the bkr is open

Question 6

Float charge voltage
Equalizing charge voltage

Answer 6

135 volts
138 volts

Question 7

What are the non vital 125vdc battery charger powered by?

Answer 7

15D/15E

Question 8

How do we get 250vdc

Answer 8

125vdc nominal in series

Question 9

What does the 250vdc load center power?

Answer 9

-Main turbine emergency bearing oil pump
-main feed pump emergency bearing oil pumps
-Air side seal oil backup pump

Question 10

What is the mi I’m I’m battery voltage?

Answer 10

105vdc