Electrical Devices & Measuremt
Electrical Devices & Measuremt TENS 2146
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This 7 page Class Notes was uploaded by Alba Tremblay on Monday October 12, 2015. The Class Notes belongs to TENS 2146 at Georgia Southern University taught by Maria Alba-Flores in Fall. Since its upload, it has received 38 views. For similar materials see /class/222032/tens-2146-georgia-southern-university in Engineering and Tech at Georgia Southern University.
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Date Created: 10/12/15
TENS 2146 Electric Devices and bleasuremenls Georgia Southern University lMecllanical and Elec 39ical Engineering Technology Fall Semester 2009 Lecture 3 Ch1 Science of Electricity Prof AlbarFlores METEET Dept 8252009 The Nature of Matter Matter is anything that occupies space or has mass Smallest parts I Element purest form I Compound two or more elements are mixed together The Nature of Matter quotmm mm Example of Elements Example of compounds Examples of conductors semiconductors and insulators Conductors Semiconductors Insulators Copper Silicon Bakelite Iron germanium Glass Steel Gallium Arsenide Mica Aluminum Porcelain Silver Sand Tin Paper Rubber Air 8252009 Basic Electrical Circuits Resistance voltage current Ohms Law and Power Series Circuits Parallel Circuits Electric resistance a material39s opposition to the flow of electric current measured in ohms Electrical tension or voltage is the difference of electrical potential between two points of an electrical or electronic circuit expressed in volts Electrical Current is a flow of electrical charge carriers usually electrons or holes electron deficient atoms the standard unit is the ampere Ohm s Law Ohm39s Law defines the relationships between V voltage 1 current and R resistance One ohm is the resistance value through which one volt will maintain a current of one ampere VlxR Power in Electrical Circuits Electrical Power P in a circuit is the amount of energy that is absorbed or produced within the circuit The unit of measurement is the Watt W A source of energy such as a voltage will produce or deliver power while the connected load absorbs it P is the product of voltage multiplied by the current P V x I By using Ohm39s law and substituting for V I and R the formula for electrical power can be found as PV2R PszR Series Circuits Req R1 R2 R3 1ERecl 1242009 Generators Basics Energy Canversian electrical mechanical Relvver vultagE gtlt current pDWE mug X Speed INTRODUCTION r ls a rnaenlne that unvens rne nanleal Energy lnm Electrlcal Energy by uslng the prlnelple gr rnag Ell lndu lun Tnls prlnelple ls Explalned as fulluvvs Whenever a eunduemr ls muved Wltnln a magnetl rleld ln suen a Way tnat tne eundumur cuts aeruss magnetl llnes elmqu vultage ls generated ln the eeln uem TheAMOUNTufvultage generated depends eln the strength elnne rnagn t r leld 2 the angle VWlElW the eunduemr cutsthe magnetlcfleld a the speed atvvhlch the eunduemrls muved 4 the length elnne cunducturvvlthln the magnetl rleld W s ll NA 2 mm POLARlTY unne vultage depends un tne dlreetlun uf ne magnetl llnes uf ux and tne dlreetlun uf muvement uf tne eundumur lu determlne the dlremlun elf current ln a glvEn Sltuall n the LEFTVHAND RULE FOR GENERATORS ls used Q What rule should you use to delermlne he dlredlo of lnduced emfln a Col7 l bemg muved l e dlledldn ulmagnellcllux nurn nulln m sduln 39VEIUY rnlddle nngelWlll lnen puml ln me e e Puml ydullnurnb ln lne dlleelldn lne edndudd ls Pdlnlydulldlellngelln n dlvemlunulcunenllluwm n quotvalElvcullluwhlchlhevuhagel ll an s app ed MOYl N or cuNuucwR 1 242009 potE PIECES THE ELEMENTARY GENERATOR The simplest elementary generator that can be built is an AC generator An elementary generator consists ofa wirel so that it can be rotated in a stationary magne This will I roduce an induced electromotive force emf in the loop oop placed tic eld Sliding contacts brushesconnect the loop to an external 39 ed emf circuit load in order to pIck up or use the induc lOAD EXTERNAL cIRcum The Elementary Generator As tne coii rotates avultage in induced between its terminais A and D Generating an AC voltage A simpie Ac generaturwith a coii tnat rotates at so revmin petween and s poies or a permanentmagnet is The coii is connected to WEI siip rings mounted on tne snart The siip rings are connected to an external ioad by means ortWo stationary prusnes x a E v ux density 1 length urine Eunduciur v weed ufmlauun inis voltage appears petween tne prusnes and tnererore across tne ioad The voitage is maximum when tne coii is in its norizortai position when tne coii is in its vertical position The induced voltage is minimu The coii poiarity changes every time tne coii makes nair a urn D ln l ism mm 12m 66W position position position position position 6 EnEnnton tEnnnnnt vottno E Output voltage of an elementary generator I motion to 39 Q Generators convert mechanica electrical energy using what princ Q What is the purpose 0 the slip rings 39 o em induced in a rotating coil when k he passes through the neutral pla uring one revolution 1242009 DirectCurrent Generator lfthe brushes x and y could be switched from one slip ring to the other 39 p 39 39 39 voltage of constant polarity across the load Brush x could be always positive and brush y negative 5mm A This can be obtained by using a commutator A very simple commutator is a slip ring that is cut in half One segment is connected to coilend A The other segment is connected to coilend D The commulator revolves with the coil and the voltage between the segments is pickin by two stationary brushes x and y The voltage between brushes X and y pulsates but never changes polarity Pulsating DC voltage Q What component causes a generator to produce DC voltage rather than AC voltage at its output terminals POLE PIECES a Effects of additional coils This graph shows the ripple effect ofthe voltage when two armature coils are used 17 By adding more annature coils the ripple effect can be further reduced Decreasing ripple in this way increases the effective voltage of the ou put Q What is Commutation Is the process by which a DC voltage output is taken from an armature that has an AC voltage induced in it 932009 Conductors TENS 2146 Electrical Devices and Measxlrunelts Cunduclursvary dEpEndmg 0 the type ulmalena Tum whrch they are made Georgia Southern University IVIedIanilta 1nd Elemrial Fugimetim Cupper rs ah exaeueht canduclur ahu Tslhe must 39 E cummuhw used Tullnologl Fall semester 1009 suver rs better canduclurbulexpenswe Chapter 3 Basic Elect al Circuit Mate ATurmhurh rs userur hwghrvuilage apphcalmns Brass rs useurur swrtchhg parts because rts strength me A has nres Mntnuept Conductance The uhuuctahce uia materraT rhurcates haw guud a uhuucturrs The uhuuctahce rsgweh armehs 5 0T M Analogies A ucturwrth hrgh resrstahce lsmaH The cahuuctahce rsthe recrprucaT urthe resrstahce mmlam 5 am am pm wrth smaH urameter G 1 R uhuucturwrth Tuw resrstahce Marge uhuuctahce rs ahamgtu a waterprpe wrth Targe uramet r Conductor Sizes Circular M39 s Cunduclurs are srzeu hytherr crussrsemuna area Circular mils are used a express crussrseclmna CrrcuTar canduclurs iuHuw the Amencan Wrre Gauge area a uhuucturs System LAWG The Targer the gauge humher the smauerthe crussr sectruhaT area Circular MII DiameterV Examples Exam E gt uhuucturwrth a urameter all mHs has ah quot area uuzl4mus gt AGW m 14 a 64 mm mm quot A uhducturwrth a drameter 0115 MM has an gt AGW ha 20 a 32 mm drameter mHs ma HMSV 125 am 1 mH 11000 001 rhches 932009 D1mil D2mils D15mi 39 area 4 cmils area 225 cmils Figure 34 The area in circular mils is found by squaring the diameter in mils Gauge no Resistance ohms per Diameter Circular 1000 ft at 25 C 68 F mils mil area copper wu e aluminum Wire 4600 211600 004901 007930 4096 167800 006182 01000 3648 133100 007793 01261 3249 105600 009825 015 2893 83690 01264 02005 2576 66370 01593 02529 2294 52640 020 03189 2043 4 7 02533 04021 1819 33100 03195 05072 1620 26250 04028 06395 1443 20820 05080 08060 1285 16510 06405 1016 1144 13090 08077 1282 1019 10380 1018 1616 9074 3234 1284 204 8081 6530 1619 257 7196 5178 2042 324 6408 4107 2575 408 5707 3257 3247 515 Aluminum 157 ohms 3 Figure 37 Two conductors of equal diameter will have different resistance values when made lrom dillereni types of material No 12 copper wire has less resistance than a No12 aluminum wire Copper lfi ohms w v i mum luluLiquot m l w it uv39uwc z m Conductor Voltage Drop The National Electrical Code NEC has a maximum Drop Standard for Electrical circuit panels connected to electrical devices A maximum of 3 voltage drop is permissible by NEC standards Examplel Assume that a load of 8Amps is located 200 feet from a circuit break panel of 120 volts Find the gauge number AGW of cooper conductor that is required to meet the NEC standard LOAD i 8 Amps Electrical circuit panel 120 The formul is needed t CMA K t l VD Conductor Voltage Drop cont a for calculating the size ofthe conductor that 0 stay within the 3 limit is CMAKXIXL VD area in circular mils material constant e g for cooper is 12 for aluminum is 18 amperage through the conductor length of the conductor voltage drop