Which relays are energized when power is applied to the bus, according to the system?

Which relays are energized when power is applied to the bus, according to the system?

• A. PCC only
• B. PCC and TCC
• C. TCC only
• D. None

Answer: (B)

Relays that are connected directly to the bus power will energize as soon as the bus voltage comes up. In this system, both the PCC and the TCC coils are fed from the bus, so when power is applied, both relays pull in. That activates both control paths—the one for power conditioning and the other for trip/control sequencing—ensuring the system is armed and ready to operate. If only one coil were fed, only that path would activate; if neither coil is fed, the control circuitry would stay inactive.

Relays that are connected directly to the bus power will energize as soon as the bus voltage comes up. In this system, both the PCC and the TCC coils are fed from the bus, so when power is applied, both relays pull in. That activates both control paths—the one for power conditioning and the other for trip/control sequencing—ensuring the system is armed and ready to operate. If only one coil were fed, only that path would activate; if neither coil is fed, the control circuitry would stay inactive.