How many TRUs does the aircraft have and what are they rated at?

• A. 2 TRUs at 60 Amps each
• B. 3 TRUs at 100 Amps each
• C. 4 TRUs at 120 Amps each
• D. 5 TRUs at 150 Amps each

Answer: (C)

Transformer Rectifier Units convert DC power from the aircraft’s sources into 115 VAC at 400 Hz to feed the AC electrical system. The number and size of TRUs are set by the aircraft’s electrical design to provide enough power with redundancy. On this aircraft there are four TRUs, each capable of 120 amps. This arrangement gives a total capacity of 480 amps, which supplies normal loads and still keeps essential systems powered if one TRU is unavailable. The 120-amp rating is a common, balanced choice for regional jets, providing ample headroom without excessive weight or wiring. Other configurations, like fewer TRUs at lower ratings, would risk insufficient power during peak loads or during start, while more TRUs at higher ratings would add unnecessary weight and complexity.