28 VDC GPU Converters

Ground power units (GPUs), developed by SUPSONIK, S.L. are equipment intended for installation at airports, with the aim of supplying aircraft utilities when their generator is disconnected.

In general conditions, the characteristics of the supply voltage of aircrafts are very different from those of a conventional network. These ground units convert the distribution network voltage and adapt it to the needs of aircrafts.


GPUs have a voltage drop compensation system in the power cable which regulates voltage according to the characteristics of the cable to ensure that voltage value at aircraft connector remains constant, regardless of the load applied.

28 Vdc GPUs have two operating states; Activated and Service. In activated state, the 28 Vdc unit is idle delivering a correct voltage to terminals before output contactor. The GPU is ready to provide service to the aircraft. The operating state is that in which - from the activated state - the output contactor has been closed and the unit supplies power to the aircraft at 28Vdc.

On the other hand, in order to facilitate equipment handling, two operation modes are available; Normal and Automatic. In normal mode, we press the operation button each time power is needed. In automatic mode - once the cable of an airplane is disconnected - the system waits for a certain time - without output voltage - without equipment disconnection. If another aircraft is connected in that time interval, the equipment will start up again, without the need to make a manual command.

To detect that a load has been connected, the GPU receives two signals from the aircraft. One is a potential-free signal indicating that the cable is connected, and the other one is a 28 V permit to indicate that connection can be made.

The equipment is easily transportable in four-wheel cart - two of them guide wheels -that is supplied along with the equipment as a whole. The carriage is provided with a hitch to allow being towed by another vehicle. It is also provided with a braking device which is released only in towing position, and incorporates a support to store output cables during transport.

Main features of 400 Hz GPU converters:

  • Output current 400 A, 600 A.
  • Input Voltages ~ 3 400 Vac ± 15% (consult other versions).
  • Input Frequency 50/60 Hz
  • Voltage output 28 Vdc (adjustable).
  • Ripple at output voltage 2% (Full load).
  • Input power factor PF ≥ 0.9
  • Easily transportable.
  • Air cooling.
  • Air cooling
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