Which component maintains a constant voltage and frequency despite engine speed variations and load changes?

• A. Constant-Speed Drive
• B. Integrated Drive Generator
• C. Transformer-Rectifier Unit
• D. Standby/EMERGENCY Bus

Answer: (B)

The device that keeps both voltage and frequency steady as engine speed and load change is the integrated drive generator. It combines a generator with a constant-speed drive and an automatic voltage regulator. The constant-speed drive keeps the generator shaft spinning at a fixed speed even when the engine RPM varies, which maintains a constant electrical frequency. Meanwhile, the automatic voltage regulator senses the output and adjusts the generator’s field excitation so the output voltage stays within the required level as load changes. This combination provides stable, regulated AC power for the aircraft electrical system.

Other components don’t do both tasks. A constant-speed drive alone would preserve generator speed (and thus frequency) but wouldn’t regulate voltage by itself. A transformer-rectifier unit converts AC to DC and doesn’t maintain AC voltage/frequency. A standby/EMERGENCY bus is a power path or bus for emergencies, not a device that continuously regulates voltage and frequency under normal operation.