Download - Tablas y Fórmulas de Electricidad
Curso sobre sistemas trifsicos
Manandes SCCI calle 10 #1004 y Av. 10 Manta- Ecuador
Formacin Tcnica Div. Tele/fax 624078 626652 email: [email protected]
E = Voltage / I = Amps /W = Watts / PF = Power Factor / Eff = Efficiency / HP = HorsepowerAC/DC Formulas
To FindDirect CurrentAC / 1phase 115v or 120vAC / 1phase208,230, or 240vAC 3 phaseAll Voltages
Amps whenHorsepower is KnownHP x 746E x EffHP x 746E x Eff X PFHP x 746E x Eff x PFHP x 7461.73 x E x Eff x PF
Amps whenKilowatts is knownkW x 1000EkW x 1000E x PFkW x 1000E x PFkW x 10001.73 x E x PF
Amps whenkVA is knownkVA x 1000EkVA x 1000EkVA x 10001.73 x E
KilowattsI x E1000I x E x PF1000I x E x PF1000I x E x 1.73 PF1000
Kilovolt-AmpsI x E1000I x E1000I x E x 1.731000
Horsepower(output)I x E x Eff746I x E x Eff x PF746I x E x Eff x PF746I x E x Eff x 1.73 x PF746
Three Phase Values
For 208 volts x 1.732, use 360For 230 volts x 1.732, use 398For 240 volts x 1.732, use 416For 440 volts x 1.732, use 762For 460 volts x 1.732, use 797For 480 Volts x 1.732, use 831
E = Voltage / I = Amps /W = Watts / PF = Power Factor / Eff = Efficiency / HP = HorsepowerAC Efficiency and Power Factor Formulas
To FindSingle PhaseThree Phase
Efficiency746 x HPE x I x PF746 x HPE x I x PF x 1.732
Power FactorInput WattsV x AInput WattsE x I x 1.732
Power - DC Circuits
Watts = E xI
Amps = W / E
Ohm's Law / Power Formulas
P = watts
I = ampsR = ohmsE = Volts
Voltage Drop Formulas
Single Phase(2 or 3 wire)VD =2 x K x I x LCMK = ohms per mil foot
(Copper = 12.9 at 75)
(Alum = 21.2 at 75)
Note:K value changes with temperature. See Code chapter 9, Table 8L = Length of conductor in feet
I = Current in conductor (amperes)
CM = Circular mil area of conductor
CM=2K x L x IVD
Three PhaseVD=1.73 x K x I x LCM
CM=1.73 x K x L x IVD
Calculating Motor Speed:A squirrel cage induction motor is a constant speed device. It cannot operate for any length of time at speeds below those shown on the nameplate without danger of burning out.
To Calculate the speed of a induction motor, apply this formula:Srpm = 120 x F PSrpm = synchronous revolutions per minute.120 = constantF = supply frequency (in cycles/sec)P = number of motor winding poles
Example: What is the synchronous of a motor having 4 poles connected to a 60 hz power supply?
Srpm = 120 x F PSrpm = 120 x 60 4Srpm = 7200 4Srpm = 1800 rpm
Calculating Braking Torque:Full-load motor torque is calculated to determine the required braking torque of a motor.To Determine braking torque of a motor, apply this formula:T = 5252 x HP rpmT = full-load motor torque (in lb-ft)5252 = constant (33,000 divided by 3.14 x 2 = 5252)HP = motor horsepowerrpm = speed of motor shaft
Example: What is the braking torque of a 60 HP, 240V motor rotating at 1725 rpm?
T = 5252 x HP rpmT = 5252 x 60 1725T = 315,120 1725T = 182.7 lb-ft
Calculating Work:Work is applying a force over a distance. Force is any cause that changes the position, motion, direction, or shape of an object. Work is done when a force overcomes a resistance. Resistance is any force that tends to hinder the movement of an object.If an applied force does not cause motion the no work is produced.
To calculate the amount of work produced, apply this formula:
W = F x DW = work (in lb-ft)F = force (in lb)D = distance (in ft)
Example: How much work is required to carry a 25 lb bag of groceries vertically from street level to the 4th floor of a building 30' above street level?
W = F x DW = 25 x 30W = 750 -lb
Calculating Torque:Torque is the force that produces rotation. It causes an object to rotate. Torque consist of a force acting on distance. Torque, like work, is measured is pound-feet (lb-ft). However, torque, unlike work, may exist even though no movement occurs.
To calculate torque, apply this formula:T = F x DT = torque (in lb-ft)F = force (in lb)D = distance (in ft)Example: What is the torque produced by a 60 lb force pushing on a 3' lever arm?
T = F x DT = 60 x 3T = 180 lb ft
Calculating Full-load Torque:Full-load torque is the torque to produce the rated power at full speed of the motor. The amount of torque a motor produces at rated power and full speed can be found by using a horsepower-to-torque conversion chart. When using the conversion chart, place a straight edge along the two known quantities and read the unknown quantity on the third line.
To calculate motor full-load torque, apply this formula:T = HP x 5252 rpmT = torque (in lb-ft)HP = horsepower5252 = constantrpm = revolutions per minuteExample: What is the FLT (Full-load torque) of a 30HP motor operating at 1725 rpm?
T = HP x 5252 rpmT = 30 x 5252 1725T = 157,560 1725T = 91.34 lb-ft
Calculating Horsepower:Electrical power is rated in horsepower or watts. A horsepower is a unit of power equal to 746 watts or 33,0000 lb-ft per minute (550 lb-ft per second). A watt is a unit of measure equal to the power produced by a current of 1 amp across the potential difference of 1 volt. It is 1/746 of 1 horsepower. The watt is the base unit of electrical power. Motor power is rated in horsepower and watts.Horsepower is used to measure the energy produced by an electric motor while doing work.
To calculate the horsepower of a motor when current and efficiency, and voltage are known, apply this formula:HP = V x I x Eff 746HP = horsepowerV = voltageI = curent (amps)Eff. = efficiencyExample: What is the horsepower of a 230v motor pulling 4 amps and having 82% efficiency?HP = V x I x Eff 746HP = 230 x 4 x .82 746HP = 754.4 746HP = 1 Hp
Eff = efficiency / HP = horsepower / V = volts / A = amps / PF = power factor
Horsepower Formulas
To FindUse FormulaExample
GivenFindSolution
HPHP = I X E X Eff. 746240V, 20A, 85% Eff.HPHP = 240V x 20A x 85% 746HP=5.5
II = HP x 746 E X Eff x PF10HP, 240V, 90% Eff., 88% PFII = 10HP x 746 240V x 90% x 88%I = 39 A
To calculate the horsepower of a motor when the speed and torque are known, apply this formula:HP = rpm x T(torque) 5252(constant)Example: What is the horsepower of a 1725 rpm motor with a FLT 3.1 lb-ft?HP = rpm x T 5252HP = 1725 x 3.1 5252HP = 5347.5 5252HP = 1 hp
Calculating Synchronous Speed:AC motors are considered constant speed motors. This is because the synchronous speed of an induction motor is based on the supply frequency and the number of poles in the motor winding. Motor are designed for 60 hz use have synchronous speeds of 3600, 1800, 1200, 900, 720, 600, 514, and 450 rpm.
To calculate synchronous speed of an induction motor, apply this formula:rpmsyn = 120 x f Nprpmsyn = synchronous speed (in rpm)f = supply frequency in (cycles/sec)Np = number of motor polesExample: What is the synchronous speed of a four pole motor operating at 50 hz.?
rpmsyn = 120 x f Nprpmsyn = 120 x 50 4rpmsyn = 6000 4rpmsyn = 1500 rpm
Options: - Useful Formulas- Motor Formulas
To better understand the following formulas review the rule of transposition in equations.A multiplier may be removed from one side of an equation by making it a division on the other side, or a division may be removed from one side of an equation by making it a multiplier on the other side.
1. Voltage and Current: Primary (p) secondary (s)Power(p) = power (s) or Ep x Ip = Es x IsA.Ep =Es x IsIpB.Ip =Es x IsEp
C.Is =Ep x IpEsD.Es =Ep x IpIs
2. Voltage and Turns in Coil:Voltage (p) x Turns (s) = Voltage (s) x Turns (p)or Ep x Ts = Es x IpA.Ep =Es x IpTsB.Ts =Es x TpEp
C.Tp =Ep x TsEsD.Es =Ep x TsTp
3. Amperes and Turns in Coil:Amperes (p) x Turns (p) = Amperes (s) x Turns (s)or Ip x Tp = Is x TsA.Ip =Is x TsTpB.Tp =Is x TsIp
C.Ts =Ip x TpIsD.Is =Ip x TpTs
FLA Motor Chart Options:
DC motors
AC Single Phase AC 2 Phase (4 wire) Induction Type Squirrel Cage and Wound Rotor
AC 3 Phase Induction Type Squirrel Cage and Wound Rotor
AC 3 Phase Synchronous Type Unity Power Factor
DC Motors
Horse-power90v120v180v240v500v550v
Amperes
1/44.03.12.01.6----
1/35.24.12.62.0----
1/26.85.43.42.7----
3/49.67.64.83.8----
112.29.56.14.7----
1-1/2--13.28.36.6----
2--1710.88.5----
3--251612.2----
5--402720----
7-1/2--58--2913.612.2
Horse-power90v120v180v240v500v550v
Amperes
10--76--381816
15------381816
20------552724
25------894338
30------1065146
40------1406761
Horse-power90v120v180v240v500v550v
Amperes
50------1738375
60------2069990
75------255123111
100------341164148
125------425205185
150------506246222
200------675330294
AC Single Phase Motors
Horse-power115v200v208v230v
Amperes
1/64.42.52.42.2
1/45.83.33.22.9
1/37.24.14.03.6
1/29.85.65.44.9
3/413.87.97.66.9
1169.28.88.0
1-1/22011.51110
22413.813.212
33419.618.717
55632.230.828
7-1/280464440
1010057.55550
Horse-power115v200v208v230v
2 Phase (4 wire) AC Induction TypeSquirrel Cage and Wound Rotor
Horse-power115v230v460v575v2300v
Amperes
1/24.02.01.00.8--
3/44.82.41.21.0--
16.43.21.61.3--
1-1/29.04.52.31.8--
211.85.93.02.4--
3--8.34.23.3--
5--13.26.65.3--
10--241210--
15--361814--
20--472319--
25--592924--
30--693528--
40--904536--
Horse-power115v230v460v575v2300v
Amperes
50--1135645--
60--133675314
75--166836618
100--2181098723
125--27013510828
150--31215612532
200--41620816743
AC 3 Phase Induction Type Squirrel Cage and Wound Rotor
Horse-power115V200V208V230V460V575V2300V
Amperes
1/24.42.52.42.21.10.9--
3/46.43.73.53.21.61.3--
18.44.84.64.22.11.7--
1-1/212.06.96.66.03.02.4--
213.67.87.56.83.42.7--
3--11.010.69.64.83.9--
5--17.516.715.27.66.1--
7-1/2--25.324.222119--
Horse-power115v200v208v230v460v575v2300v
10--32.230.8281411--
15--48.346.2422117--
20--62.159.4542722--
25--78.274.8683427--
30--9288804032--
40--1201141045241--
Horse-power115v200v208v230v460v575v2300v
50--1501431306552--
60--177169154776216
75--221211192967720
100--2852732481249926
125--35934331215612531
150--41439636018014437
200--55252848024019249
Horse-power115v200v208v230v460v575v2300v
Amperes
250--------30224260
300--------36128972
350--------41433683
400--------47738295
450--------515412103
500--------590472118
AC 3 Phase Synchronous Type Unity Power Factor
Horse-power230v460v575v2300v
Amperes
25532621--
30633226--
40834133--
501045242--
60123614912
75155786215
1002021018120
12525312610125
15030215112130
20040020116140
Horse-power230v460v575v2300v
Formato base
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