When is an inverter typically used in an aircraft power system?

• A. To regulate the 28V DC bus
• B. To charge the battery
• C. To provide DC power to avionics
• D. To convert DC to AC to power equipment that requires AC power when AC power is unavailable

Answer: (D)

Inverters convert DC power to AC power, allowing equipment that requires AC to run when no AC source is available. In an aircraft, engines or external power typically provide AC, but the inverter backs up by supplying AC from the DC system (battery or DC bus) during start, abnormal conditions, or when AC power is offline. That’s why this option describes converting DC to AC to power equipment that needs AC when AC power isn’t available. The other options describe DC-side functions: regulating the DC bus, charging the battery, or supplying DC to avionics, which aren’t the inverter’s primary purpose.