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Practical aircraft generating systems

 Practical aircraft generating systems

Generators are a primary source of power in an aircraft and can either produce direct or alternating current (DC or AC) as required.

 

They are driven by a belt drive (in smaller aircraft), or engine/APU accessory gearbox in larger aircraft. Generators will have sufficient output to supply all specified loads and charge the battery(s).

 

Most avionic equipment requires a regulated and stable power supply depending on its function, e.g. in the case of lighting, it would be inconvenient if the intensity of lighting varied with engine speed.

 

 The generator output is affected by internal heat and this has to be dissipated. Cooling methods can include natural radiation from the casing, however, this is inadequate for high-output devices where ram-air is

directed from a scoop and directed into the generator’s brush-gear and commutator.

 

 In some installations, e.g. helicopters, a fan is installed to provide cooling when the aircraft is hovering. We know from basic theory that a generator’s output will vary depending on the input shaft speed.

 

 A means of regulating the generator’s output to the bus is required as is a means of overload protection.

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