What is Aircraft Power Generation System?
Whether an aircraft is in flight, on the ground, or taxiing, most require some sort of electrical power generation in order to operate electrical systems such as the NAV radio, intercoms, and transponder, Depending on the type of aircraft and its electrical needs, a number of methods may be used for power generation, ranging from batteries to alternators. In this blog, we will discuss the most common sources of aircraft power generation, allowing you to better understand how the electrical systems of aircraft are provided power.
One of the oldest and most common forms of electrical generation on aircraft comes in the form of the power generator, distinguishable by its use of a stationary permanent magnet and rotating coil. In order to create electricity, an armature with wounded wires rotates through a magnetic field, and electricity is induced to the wires before being transferred to stationary carbon brushes that are placed against the commutator of the armature. The output of generators is DC voltage, and this type of voltage is used to power electrical systems on the aircraft. For the generator to provide sufficient power for flight operations, the RPM of the aircraft engine needs to be above 1,200 so that the batteries can be charged. When an aircraft is not in flight and is taxiing, the batteries of the aircraft become the primary source of power.
As compared to the power generator, the alternator is another common form of power generation that utilizes a rotating magnetic field within a stationary coil. Typically, an alternator creates its magnetic field through an electromagnet, which is a coil that has a core made from iron. To start the alternator, power must be provided by aircraft batteries, thus they cannot generate electricity with a dead battery. Alternators also generate electricity that is AC voltage, and internal diodes help rectify the power into DC voltage that may be used by electrical components. As compared to a generator, the alternator is much lighter and can create more power even while idling, making them highly beneficial for a number of aircraft types and applications.
For the batteries of the aircraft, the two main types come in the form of primary and secondary cell batteries. Primary cell batteries are those that are unable to be charged, and zinc-carbon and alkaline battery types are the most common. Secondary cell batteries, on the other hand, are able to be recharged, and common types include the lead acid battery, nickel cadmium, silver-zinc, nickel metal-hydride, and lithium battery. Despite each battery type falling into one of the two categories, each chemical features very unique characteristics that operators should be well aware of to ensure safe operation and handling.
For a lead acid battery to function, two dissimilar electrodes act as conductors within an electrolyte, and the chemical reaction between electrodes and chemicals cause electrons to be attracted to the negative electrode. This results in a low amount of electrons in the positive terminal, and voltage begins to build up in each cell with 2.1 volts per cell. With a NiCad battery, 1.2 volts are stored in each cell, and thus 10 cells are required for a standard 12 volt model. Lithium batteries may range in cell voltage from 1.5 to 4 volts, and they typically provide a much longer life and charge density as compared to some other batteries. Despite this, they require special chargers and may have increased costs as well.
On some aircraft, power may be provided by solar cell sources, otherwise known as photovoltaic cells. With such cells, photons from a variety of light sources are captured by semiconductor materials within cells, allowing for the generation of electricity. Solar cell systems often have an efficiency of 20% to 25%, meaning that sunlight can provide around 337 watts with a 90 degree angle between the cell and the sun. While larger aircraft are unable to truly utilize solar cells for their electricity generation, such cells are sometimes used for glider batteries.
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