In the aircraft electrical system, which device connects a generator to the synchronizing bus?

• A. Bus tie breaker
• B. Automatic switch
• C. Circuit breaker
• D. Relay

Answer: (A)

The device that connects a generator to the synchronizing bus is the bus tie breaker. Its job is to physically tie two bus bars together so the generator can feed the synchronizing bus and operate in parallel with other sources. When the generator is brought online and is in the correct voltage and frequency range, the bus tie breaker closes, allowing power to flow onto the bus. It stays closed for normal parallel operation and opens to isolate the generator if needed, such as for faults or maintenance.

A circuit breaker is primarily a protection device that interrupts fault currents, not specifically designed to connect a generator to the bus during normal operation. An automatic switch might handle automated source transfer, but the direct connection between the generator and the synchronizing bus is accomplished by the bus tie breaker. A relay controls signals and protection logic, not the actual heavy-duty connection between the generator and the bus.