TRU-28 - Transformer Rectifier

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The TRU–28 transformer rectifier unit will start and power all known 28V DC aircraft. Environmentally clean and easy to use, the unit offers users significant operating benefits.

Typical applications:

  • Hangar and apron
  • Continuous current and starting
  • No batteries
  • Flexible use

Designed in collaboration with Powervamp and built to the highest industry standards (MILSTD 704, ISO 6858), it produces the highest quality output signal with minimal AC ripple and is guaranteed to be accepted by all DC aircraft.

The 12 pulse rectification technology used ensures a low input total harmonic distortion at nominal loads, adding to the efficiency of the system.

The TRU–28 produces a regulated 28V DC output and can deliver a constant current of 600A with engine starting peaks of up to 2400A. The current limiting feature enables the user to limit the output current to the aircraft and can be accessed and set via the digital display. The user can access the line drop compensation feature via the display menu to increase/decrease the output voltage at the plug within the limits of ISO 6858.

The TRU–28 is a compact solid state module built to IP55 protection, designed for internal/external fixed or mobile use. With its weather-resistant, stainless steel case with large caster wheels, the unit can be easily moved by hand over uneven surfaces.

Power consumption is reduced by the unique ‘wake/sleep’ feature which powers down the TRU–28 after sensing that there has been no current draw for a pre-set time.

This unit includes a 100-foot (30.48 m) input cable and a 20-foot (6.1 m) output cable. Cables are pig-tailed and plug-ready (no plug included).

The TRU-28 is available in two main configurations:

  • USA Model (AERO Product ID: 2010374 [White Color]) 
    Input Three Phase: 208V-480V three-phase 60Hz

  • EU Model (AERO Product ID: 2009397 [White Color]) 
    Input Three Phase: 400V three-phase +/- 10% 50/60Hz

Voltage 28V
Continuous current 600 A
Electricity 2400 A
Protection class IP55

  • Low total input harmonic distortion

  • Digital display
  • Unique energy-saving sleep mode controlled via the display
  • System data logger
  • Indoor/outdoor hangar use
  • Line drop compensation
  • External system control (option)
  • Emergency power off
  • Aircraft interlock/system interlock override
  • Input frequency and voltage monitoring
  • Output current limit feature
  • Braking system
  • Input and output cable storage



  • Voltage: 208-230-240-380-440-460- 480V AC three-phase (field adjustable)
  • Frequency: 50/60Hz
  • Rectification: 12 pulse
  • Power factor: > 0.80 @ nominal load
  • Line current: 26A – 62A @ nominal load (voltage dependent)


  • Voltage: 28 V DC
  • Curren:t 600 amps continuous
  • Engine start capacity: 2400 A selectable
  • Ripple: Less than 1% at full load
  • Line drop compensation: Up to 15%

Overload Ratings 

  • 2400 A: 2 seconds
  • 2100 A: 10 seconds
  • 1800 A: 30 seconds
  • 1200 A: 40 seconds


  • Overall efficiency: Typically > 0.92 % @ nominal load
  • Stand by losses: 250 W (Electronics)
  • No load losses: 500 W (Output on)


  • Acoustic noise: 59 dB (A) @ 1 m
  • Temperature range: -40°C to +50°C (-40°F to +122°F)
  • Water ingress: IP55

  • Over/under voltage at the output
  • Over/under voltage at the Input
  • Reverse current at the output
  • Reverse polarity at the output
  • Phase sequence at the input
  • Over temperature
  • Internal PSU voltage monitoring
  • Short circuit at the output
  • Over/under voltage trip in the case that 
  • U<20 VDC for more than 4 seconds
  • U>32 VDC for more than 4 seconds
  • U<40 VDC for more than 1 second


  • ISO 6858: Aircraft ground support electrical supplies
  • MIL-704E: Aircraft electric power characteristics
  • BS 2G 219: General requirements for ground support equipment
  • EN 62040-1-1 LVD: Safety standards
  • EN 61558-2-6 LVD: Safety standards
  • EN 61000-6-2 EMC: Immunity standard
  • EN 61000-6-4 EMC: Emission standards
  • BS 2G 219: General requirements for ground support equipment

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