Chapter 4. Electrical Systems

4.2. Power distribution unit

The list of advantages of construction of power distribution unit based on alternative current generators made it the most applicable for building electrical systems of aircraft [1; 3; 8].

What is a power distribution unit ?

Power distribution unit is system that distributes electricity on board of aircraft. power distribution unit is a complex of diferent subsistems, which consists of primary power distribution unit and many standby sourses.

Alternative current based power distribution unit

The principle construction of the AC power distribution on board shown in Fig. 36. In general it consists of the following elements:
- Generator;
- Primary protection and power distribution unit;
- Subsystems voltage transformation unit and batteries;
- Secondary protection and power distribution unit.

In common way subsystems power supply of AC voltage in 115 V is primary because its generators transform the mechanical energy of the motor rotor into electricity. Subsystems supply voltage less are secondary because they are the main source of transformers and equipment that convert electricity into alternating voltage more less.

Power distribution on board of aircraft consists of a number of independent networks based on the number of engines and generators respectively (eg, left and right in the case of with two engines). The composition of each network is stumu generator connected to the engine manual transmission with control and protection equipment.

Fig. 36. The principle construction of the AC power distribution

In the event of failure of one of its sources of supply network automatically switches to another power source.This the main function of power distribution unit to detect failures and provides reservation of thi equipment.

The network provides one or more backup generators and power from the ground airfield electrical outlet.

Sustainable source of power is the special equipment, which voltage three-phase current is reduced to the desired value and because Smoothing filter is fed to the grid DC.

Batteries based power supply are useed to:
- Supply a limited number of avionics when checking equipment on the ground in cases where no aerodrome Power supply and turn off the engine;
- Start the engine;
- Fuelling;
- Powered certain limited avionics systems during flight.

AVIONICS training course materials represented only in demonstrative mode. If it useful, all grammar mistakes will be corrected and more documents will be added. Let me know if you interest in avionics.
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Avionics training in details by
Ostroumov IvanOSTROUMOV Ivan, PhD
Associate Professor, www.ostroumov.sciary.com