Research The Modern Trends In Aircraft Electrical System

The Modern Trends in Aircraft Electrical System
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The aviation industry is undergoing significant technological development as witnessed in some of the major airline carriers. Modern technologies such as Power Electronic Systems (PES) and other sophisticated systems have been introduced in airlines like Airbus and Boeing. The advancement in technology has enabled aviation operators to replace traditional power solutions with modern ones that involve the use of electric appliances hence referred to as More Electric Aircraft (MEA). The concept of More Electric Aircraft has enabled substitution of traditional power devices such as pneumatic and hydraulic with better and effective electrical devices. Consequently, one electrical system has replaced about three systems of generating and distributing power. The aviation industry has therefore benefited significantly because of decline in costs of operation, decrease in the release of dangerous substances and improvement in reliability. The concept of More Electric Aircraft has facilitated designing of electrical power systems in modern airlines to use high voltage and also better Direct Current (DC) and Alternating Current (AC) connections. The DC and AC connections use various voltages in the modern airlines with about 400 VAC variable frequency, 270 VDC, and 200 VAC variable frequencies (Emandi and Ehsani, 2000). This paper will, therefore, focus on advanced electrical components and trends in the modern airlines and also their performance.
One of the advanced trends in electric production and distribution in the modern aircraft is an Electrical power generation of automatic electrical systems. The technological advancement of airlines in terms of power level and range has been on the rise over the past years. The concept of More Electric Aircraft and spreading of digital technology controlled the advanced development, hence leading to major changes in the processing of signals. To observe the revolutionary changes, we focus on various stages of voltage production and types of generators used at each phase.
One of the earliest generators used the standard voltage of about 28VDC from the year 1940 to 1950. In the case of a need for an emergency power source, one or two-unit batteries were used when there was damage to primary power sources and in the protection of the essential loads in the aircraft. As a result, the safety of aircraft was high. Consequently, the AC loads were powered by remaining high voltage of about 200 VAC. The 200 VAC type of voltage with a constant frequency was in operation since the year 1960. A more advanced technology was introduced in the year 1990 when variable frequency generators were used as sources of power in high loads. It was also necessary as a standby generator. This was a necessary step because maintenance of constant generator speed was a challenge, especially when changes occurred to the main engine speed referred to as Constant Speed Drive (CSD). Standard AC sources of electricity were necessary during the maintenance because of the complicated hydro-mechanical gear. Technologically advanced airlines such as Boeing and Airbus are using complex systems in their operations, hence increasing the power level and range to about 800kVA for Airbus A-380 and 1400kVA for Boeing B-787. (Moir and Seabridge, 2008)
Formerly, the 400Hz electrical systems used AC generators operating at about 115 VAC. However, improvement in technology has facilitated the use of integrated generators which have a constant speed. The constant speed is produced by a hydro-mechanical gear which uses complex processes. The hydro-mechanical gear has an advantage of maintaining a constant speed of the generator even though it results in high costs of operation. Another important system is the CF/VSCF Generating System that has also increased efficacy. The frequency produced by the generator is variable as a result of varying the speed of engine output. However, the AC power is supplied with at 400 Hz constant frequency because we have a DC converter working in the circuit in between the electric generation and the load. The operators of Boeing B-737 and Airbus A-340 have already integrated the Power electronic converters system to change the power of variable frequency from Alternating Current generator to 115 VAC at a constant frequency of about 400Hz (Corcau and Dinca, 2012).
Another important system is the Varying Frequency (VF) Generating System where the engine speed varies hence resulting in a varying generator frequency which ranges from about 380 Hz to 800 Hz. The generator produces the voltage of about 200V. The variable frequency produced by the generating system is beneficial to the airline operators because of its most reliable power generation mode, simple and very cheap compared to earlier systems. Besides the above-discussed systems, we have an Auxiliary Power Unit (APU) which is produced by Alternating Current Generators that are propelled by main engines. Two engines drive the generators, hence distributing the power to the electrical system of the aircraft. The Auxiliary Power Unit generator drives the third Alternating Current generator at a frequency of about 400 Hz. In the case of damage to the main generators or the Auxiliary Power Unit, Ram Air Turbine also called fuel cells act as sources of emergency power. A system of hydraulic Ra...