Which of the following is the correct IDG output voltage (volts)?

• A. 115 V
• B. 230 V
• C. 28 V
• D. 240 V

Answer: (A)

IDG outputs on modern airliners are 115 volts AC. The system is designed to deliver 115 VAC at 400 Hz, with the constant speed drive keeping the frequency stable as the engine speeds change. This 115 V standard is used because it allows compact transformers and efficient distribution for avionics, lights, and other AC equipment. Higher voltages like 230 or 240 V aren’t the standard for this aircraft’s AC power system, and 28 V is DC power, not the AC output of the generator. Therefore, 115 volts is the correct IDG output voltage.