Chapter 1 Aircraft Electrical System
**** Hidden Message ***** <P>Chapter 1 Aircraft Electrical System<BR>Chapter 1 Aircraft Electrical system<BR>• Electrical component<BR>• Storage Battery<BR>• DC & AC Generator<BR>• Control and Protection in DC Electrical<BR>System<BR>• Electrical Machine and control<BR>• Lighting<BR>When, Why Electric Energy was<BR>used in an aircraft?<BR>Electrical energy is being widely used<BR>• Clean form of energy – absence of smoke,<BR>ashes, dust, etc.<BR>• Easily convertible to light, heat,<BR>mechanical, chemical energy etc.<BR>• Easily and economically transportable by<BR>means of running cables.</P><P>• Electrical systems have been an<BR>onboard fixture since the Wright<BR>Flyer. In those days the role of<BR>electricity was limited to the magneto<BR>which provides sufficient voltage to<BR>spark the fuel/air mixture.<BR> Magnetos still supplied the spark to the<BR>engines, but 14- or 28-volt direct-current<BR>generator supplied current to operate the<BR>navigation and landing lights, the radios.<BR>Generators kept the batteries charged to<BR>operate the electric motor used to start the<BR>engines.</P>
<P>• The years between the two world wars is<BR>the golden age of aviation, improved in<BR>importance and complexity.<BR>• As the twentieth century ended, electrical<BR>systems have become just about equal in<BR>importance with the engines.<BR>• For many years, light planes exclusively<BR>used the 14-volt electrical system. Starting<BR>approximately in the early 1980s, the 28-<BR>volt system began to take over light<BR>aircraft.<BR>• The primary purpose of igniting the<BR>fuel/air mixture is still the domain of the<BR>magneto. However, the demand for<BR>electrical energy in the airplane has<BR>increased tremendously.<BR>• Jet airliners have extremely complex<BR>electrical systems and use alternating<BR>current as the primary source of electricity.<BR>• Batteries are used for emergency and<BR>backup operations and for some special<BR>applications.<BR>DEFINITIONS OF<BR>AIRCRAFT ELECTRICAL SYSTEM<BR>Electrical System<BR>An electrical system consists of an<BR>electrical power source, its power<BR>distribution system and the electrical load<BR>connected to that system.<BR>A typical aircraft electrical system<BR>consists of a primary (main) power source,<BR>emergency power source, secondary<BR>power conversion equipment, system<BR>control and protection devices,<BR>interconnection network, and power<BR>distribution system.<BR>Electrical Source<BR>The electrical equipment which produces,<BR>converts or transforms electrical power.<BR>Electrical Source<BR>Some common AC sources are identified<BR>as follows:<BR>• AC alternators<BR>• inverters<BR>• transformers<BR>• frequency changers.<BR>Electrical Source<BR>Some common DC sources are<BR>• DC generators<BR>• converters<BR>• batteries.<BR>Primary (Main) Power Source<BR>Primary Power Source<BR>A primary source is equipment that<BR>generates electrical power from energy<BR>other than electrical, and is independent<BR>of any other electrical source.<BR>Secondary Source<BR>• A secondary source<BR>is equipment that<BR>transforms and/or<BR>converts primary<BR>source power to<BR>supply electrical<BR>power to either AC<BR>or DC powered<BR>equipment .<BR>Secondary source.<BR>• A secondary source is equipment that<BR>transforms and/or converts primary<BR>source power to supply electrical power<BR>to either AC or DC powered equipment.<BR>• A secondary source is entirely dependent<BR>upon the primary source and is<BR>considered part of the load of the primary<BR>source.<BR>Emergency Power Source<BR>Emergency power<BR>In the event of a primary power source<BR>failure, emergency power is usually<BR>provided from independent auxiliary<BR>power unit (APU)-driven generator(s),<BR>ram air or hydraulically-driven<BR>generator(s), or batteries.<BR>Ground power<BR>ground power source<BR> A ground power source can be connected<BR>to the bus bar distribution system thus<BR>allowing all electrical systems to be<BR>powered independently of aircraft battery<BR>or generating systems. The source can be<BR>either a motorised generating unit or a<BR>battery unit.<BR>Nominal rating<BR>This rating is usually a continuous duty<BR>rating for specified operating conditions.<BR>Condition of Power Sources<BR>• Normal electrical power operation<BR>• Abnormal electrical power operation<BR>• Emergency electrical power operation<BR>Normal electrical power operation<BR> Normal operating conditions assumes that<BR>all of the available electrical power system<BR>is functioning correctly within Master<BR>Minimum Equipment List (MMEL)<BR>limitations (e.g. AC and/or DC Generators,<BR>Transformer Rectifier Units, Inverters,<BR>Main Batteries, APU etc.).<BR>Abnormal electrical power operation<BR> Abnormal operation occurs when a<BR>malfunction or failure in the electric<BR>system has taken place and the protective<BR>devices of the system are operating to<BR>remove the malfunction or the failure from<BR>the remainder of the system before the<BR>limits of abnormal operation are exceeded.<BR>Emergency electrical power operation<BR> Emergency operation is a condition that<BR>occurs following a loss of all normal<BR>electrical generating power sources or<BR>other malfunction that results in operation<BR>on standby power (batteries and or other<BR>emergency generating source such as an<BR>APU or Ram Air Turbine (RAT) only.<BR>Classification of electrical load<BR>• Vital (critical, emergency)<BR>• Essential<BR>• Non-essential</P>
<P>Typical Aircraft Electrical System<BR>• Primary (main) power source<BR>• Emergency power source<BR>• Secondary power conversion equipment<BR>• System control and protection devices<BR>• Interconnection network<BR>• Power distribution system</P>
<P>As a engineer, we should know the<BR>following information<BR>• electrical system operation, which<BR>describes primary and secondary power<BR>sources, bus configuration with circuit<BR>breakers and connected loads for each<BR>bus. A copy of the bus wiring diagram or<BR>electrical schematic should also be<BR>considered for inclusion in the report.<BR>As a engineer, we should know the<BR>following information<BR>• alternators and other power source<BR>description and related data (including<BR>such items as battery discharge curves,<BR>Transformer Rectifier Unit (TRU), Inverter,<BR>APU, RAT, etc.)<BR>List of Electrical Data<BR>END OF CHAPTER 1</P> Good stuff 这个东东真好
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