120v Flashcards
120v (10 cards)
STATE the function of the 120 VAC vital, the 120 VAC non-vital, and the 120/208 VAC computer distribution systems
- The 120 V AC vital instrumentation distribution system provides uninterruptible 120 V AC power to RPS, reactor control, and vital BOP instrumentation.
- The 120/208 V AC computer instrumentation distribution system provides an uninterruptible power supply to The A and B Main Plant Computers, The Security System and, The Fire Detection panels.
- The 120 V AC PA and non-vital instrumentation distribution system supplies uninterruptible power to site communication and non-vital BOP instruments and equipment.
IDENTIFY the power panels and uninterruptible power supplies associated with the 120 VAC vital, the 120 VAC non-vital, and the 120/208 VAC computer distribution systems.
TRAIN A
Inverter 1A PP - 1A
Inverter 1C PP - 1C
PP - 3C
Inverter 1E PP - 1E
PP - 11E
PP - 12E
TRAIN B
Inverter 1B PP - 1B
Inverter 1D PP - 1D
Inverter 1F PP - 1F
PP - 11F
EXPLAIN how an UPS produces 120 VAC output power when:
• The 480 VAC input power supply is available
• The 480 VAC input power supply is not available
- The 480 VAC input power supply is available - FROM 480VAC
- The 480 VAC input power supply is not available - FROM DC SUPPLY
DESCRIBE the meter indications that would be observed on the 120 VAC vital bus ground detection system if one side of the bus had a ground
• The voltmeter connected to the grounded side will indicate a lower voltage and the ungrounded voltmeter will indicate a higher voltage
DESCRIBE the function of a static transfer switch and IDENTIFY each 120 VAC vital power panel provided with a static transfer switch
- Manual transfer from UPS to maintenance supply (break before make) was causing momentary loss of vital instrument power causing actuation signals for various components.
- STS provides fast transfer to prevent these occurrences.
- Automatically switch from the UPS output to the maintenance supply and back again.
- The transfer switch constantly monitors the availability and synchronism of the two power supplies.
- The switch is normal source seeking, meaning that if the UPS is functioning properly, it will shift back to that source.
- This is on PP-1E & 1F
IDENTIFY the two major components of an uninterruptible power supply (UPS), and STATE their function
- Inverter converts DC to 120 AC volts
* Rectifier Assembly converts 480 VAC supplied by the vital MCC to a DC voltage
STATE the purpose of the vital AC instrument bus interlocks between the maintenance power supply and the inverter power supply
• prevents paralleling the UPS with the backup (maintenance) supply
SUMMARIZE the procedural steps to place in or remove from service a static inverter.
Start-up of 75 KVA Unit (1A-1D)
• Close the supply breakers to the inverter:
- AC supply breaker
- DC supply breaker
• Close the battery input breaker
• Check AC input voltage
- If ~ 465V, close rectifier AC input breaker
• Hold precharge PB for 5 sec.-continue holding.
• Close inverter DC input breaker
• Release precharge PB
• Close the AC output breaker
SUMMARIZE the procedural steps to transfer a vital (120 V) instrument bus power supply.
- At MCC Check closed/close maintenance supply feeder
- Loosen then nut on the mechanical interlock plate
- Open the normal supply breaker
- Close the maintenance supply breaker
- Tighten the nut
SUMMARIZE the procedural steps to transfer a non-vital (120 V) instrument power supply.
• Bus transfers are covered by procedures: “Removing inverter ED-I-4 from service” and “Total deenergization of ED-I-4 for maintenance”.
- "Removing inverter ED-1-4 from service" routes power through static transfer switch from MCC-141. - "Total deenergization of ED-I-4 for maintenance" routes power through manual transfer switch.
