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What is the purpose of an inverter?
Takes its input from 125vDC and converts it to 120vAC for vital ac buses
What is the purpose of a CVT?
Steps down the 480 vAC from an MCC to 120vAC which is used as an alternate source of vital AC supplied to the inverters
What is normally supplying the DC loads with power from the DC buses?
The battery charger or chargers that are connected to the DC bus
What is the purpose of the vital 120vAC and 125vDC systems?
To provide sources of reliable power for equipment in order to bring the plant to a safe shutdown and maintain a safe shutdown in the event of a loss of all AC power.
What loads would NOT be powered from the non-vital auxiliary 125vDC bus 3D31
3D 480 Volt Load Center DC controls
The design basis of the 125vDC vital batteries requires the vital DC battery banks to provide DC power to its shutdown loads for how long following a loss of all AC power.
What are the setpoints for the vital DC battery banks low voltage alarm ____ and the design DC voltage low limit _____?
List the 4 vital 125vDC buses
3A, 3B, 4A, 4B
What is the purpose of the 5 Kirk key locked switches designated K-1?
To ensure that vital DC buses are not inadvertently tied together through the D50 swing bus.
Why should the spare battery charger never be tied to a vital DC bus?
The spare DC battery charger is not vital equipment therefore not tested at the same level as vital equipment
Where is the 3D60 switch located?
In the MG set room in back of the cable spreading room near the 3A battery bank
What is the switch 4S77 used for?
Used to provide DC control power from unit 3 DC to the 4H 480 Volt Load Center
What is the purpose of the 3Y01B Alternate Source Transfer Switch
Used to connect the CVT 3Y01A to the Spare Inverter 3Y04 (AS)
What are the consequences of losing the 3A battery bank when connected to the 3A vital DC bus?
A battery bank must be connected to the 3A vital bus to avoid a loss of all DC power to the bus in the event of a loss of the 3A and 4B 4KV buses
What are the normal positions for the 3A and AS inverters static sync reference switches
3A in normal and AS in external
When testing for a DC ground on the 3D01 vital DC bus what method can be used to determine if a ground is present?
Press the installed ground test button. If the white light on the top goes dimmer then the bottom light, the ground is on the positive leg of the bank.
Vital Non Vital DC / AC