High Power Computerized Airborne Power Supply Unit

The APS functions as a central Power Supply for various electronic assemblies. Built for transport aircraft and meet the environment conditions as applicable for this class of aircraft. The APS is powered by the aircraft 28VDC supply per MIL-STD-704B. All APS modules outputs are fully isolated from the main input and chassis All of the outputs return lines are common. The APS contains both current and output voltage monitoring display. The APS is remote controlled. The control data is supplied via its front panel interface.

Output Voltage Characteristics

All modules output voltages are easily adjustable in ±12% range.

Voltage Stability Static variation

For the 5V outputs – 0.1V max.
For the -5V outputs – 0.05V max
For the ±15V outputs – 0.1V max.

Dynamic variation

In case of a change in load from 30% to 90% of maximum load, and back, the maximum voltage drop is 5% over maximum time period of 50usec.

Continuous overload with no damage

110% of nominal for 10 minutes over all environmental conditions.

Minimum efficiency

80% over all temperature and maximum load

Over current/short circuit protection

The APS is not damaged by over load or short circuit conditions in any of its outputs for indefinite period of time as required in MIL STD 454 req. #8 for class 1 equipment.

The minimal current, which triggers the protection when overload occurs, is 110% of Max. current.

In the event of over-load the power supply makes periodical attempts to recover, and to return to normal operation within 0.5 Sec. after the removal of the over-load.

Monitoring and Recording

During Flight voltage, current and temperature of each power supply of the APS are measured and reported via a serial port (RS-232) to an external connector on the panel. The measurement is compared to a fixed threshold. An Event is defined when a measurement passes pre-defined limits and disappears when the measurement is within limits. The refresh rate of the measurement is ~ 1-2 sec. The setting of the thresholds is defined by the End User. Events that are above or below the the normal thresholds are stored in the non-volatile memory with the following parameters:

  • Elapsed time from POWER ON.
  • The Power Supply module for which the event occurred.
  • Type of measurement and it value – voltage, current or temperature.

The raw data values stored in the Flash can be milked after the flight and displayed on Notebook with their true physical values.


Temperature range:

Operating -40°C – 71°C;
Non-operating: -40°C – +90°C;

Relative humidity:

The APS shall operate when exposed to a relative humidity of 95% in temperature of 55° C with condensation according to MIL-E-5400T.


The APS shall operate when exposed to fungus growth according to MIL-E-5400T.

Salt fog

The APS shall operate when exposed to Salt fog according to MIL-E-5400T.


The MTBF shall be 20000 operating hrs.


MIL-STD-461C Categories CE03, RE02, RS03, CS02

Size & weight

APS unit dimensions are:
Length: 22.02 inch including gripping handles.
Width: 15.47 inch.
Height: 7.80 inch
Weight is 27 Kg

Maximum overshoot

105% of nominal, for 50ms max.

Ripple & Spikes

The ripple values are measured in adjacent to the power supply output connectors, with a 1uF ceramic capacitor connected in parallel to the inspection points. The inspection bandwidth is 20MHz.

Thermal protection

In the event of over-temperature the APS shuts down, without causing any damage to its components.
The Power Supply Overtemp protection will not trigger when the power supply will operate at full load over the full ambient operation range (-20°C – 71°C)
When triggered , the Overtemp protection will automatically reset when the failure that has caused the Overtemp has been removed.


The APS shall operate as specified after being subjected to operational vibration according to MIL-STD-810F for cargo planes per MIL-STD-810F.


The APS shall operate as specified after being subjected to operational shock as encountered on board cargo planes per MIL-STD-810F.