DC power is supplied by ________.

• A. Four Transformer Rectifier Units
• B. Two Transformer Rectifier Units
• C. Three Transformer Rectifier Units
• D. Five Transformer Rectifier Units

Answer: (A)

DC power on many aircraft comes from Transformer Rectifier Units, which take AC power from the generators and convert it into DC to feed the DC buses used by avionics, lighting, and other systems. Four TRUs are installed to provide enough current and to share load, giving redundancy. With four units, the system can continue to supply DC power even if one TRU is offline or undergoing maintenance, ensuring essential systems stay powered. Fewer TRUs would reduce capacity and redundancy, which is why four is the correct setup in this context.