Tablas y formulas electricas






De interes: Tablas y formulas electricas.

E = Voltage / I = Amps /W = Watts / PF = Power Factor / Eff = Efficiency / HP =Horsepower

AC/DC Formulas
To Find Direct Current AC / 1phase
115v or 120v
AC / 1phase
208,230, or 240v
AC 3 phase
All Voltages
Amps when
Horsepower is Known
HP x 746
E x Eff
HP x 746
E x Eff X PF
HP x 746
E x Eff x PF
HP x 746
1.73 x E x Eff x PF
Amps when
Kilowatts is known
kW x 1000
E
kW x 1000
E x PF
kW x 1000
E x PF
kW x 1000
1.73 x E x PF
Amps when
kVA is known
kVA x 1000
E
kVA x 1000
E
kVA x 1000
1.73 x E
Kilowatts I x E
1000
I x E x PF
1000
I x E x PF
1000
I x E x 1.73 PF
1000
Kilovolt-Amps I x E
1000
I x E
1000
I x E x 1.73
1000
Horsepower
(output)
I x E x Eff
746
I x E x Eff x PF
746
I x E x Eff x PF
746
I x E x Eff x 1.73 x PF
746
Three Phase Values
For 208 volts x 1.732, use 360
For 230 volts x 1.732, use 398
For 240 volts x 1.732, use 416
For 440 volts x 1.732, use 762
For 460 volts x 1.732, use 797
For 480 Volts x 1.732, use 831

 

E = Voltage / I = Amps /W = Watts / PF = Power Factor / Eff = Efficiency / HP =Horsepower

AC Efficiency and Power Factor Formulas
To Find Single Phase Three Phase
Efficiency 746 x HP
E x I x PF
746 x HP
E x I x PF x 1.732
Power Factor Input Watts
V x A
Input Watts
E x I x 1.732
Power – DC Circuits
Watts = E xI
Amps = W / E
Ohm’s Law / Power Formulas

 

clip_image001 = watts

= amps

R = ohms

E = Volts

Voltage Drop Formulas
Single Phase
(2 or 3 wire)
VD = 2 x K x I x L
CM
K = ohms per mil foot
(Copper = 12.9 at 75°)
(Alum = 21.2 at 75°)

Note: value changes with temperature. See Code chapter 9, Table 8

 

L = Length of conductor in feet
I  = Current in conductor (amperes)
CM
 = Circular mil area of conductor

CM= 2K x L x I
VD
Three Phase VD= 1.73 x K x I x L
CM
CM= 1.73 x K x L x I
VD

 

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
            P

Srpm = synchronous revolutions per minute.
120   = constant
F       = 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
            P
Srpm = 120 x 60
            4
Srpm = 7200

             4
Srpm = 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
    rpm

T      = full-load motor torque (in lb-ft)
5252 = constant (33,000 divided by 3.14 x 2 = 5252)
HP    = motor horsepower
rpm = speed of motor shaft

Example: What is the braking torque of a 60 HP, 240V motor rotating at 1725 rpm?

T = 5252 x HP
    rpm
T = 5252 x 60
     1725
T = 315,120
     1725
T = 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 D

W = 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 D
W = 25 x 30
W = 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:

= F x D

T = 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?

= F x D
= 60 x 3
= 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
    rpm

T = torque (in lb-ft)
HP = horsepower
5252 = constant
rpm = revolutions per minute

Example: What is the FLT (Full-load torque) of a 30HP motor operating at 1725 rpm?

T = HP x 5252
    rpm
T = 30 x 5252
     1725
T = 157,560
     1725
T = 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
        746

HP = horsepower
   = voltage
    = curent (amps)
Eff. = efficiency

Example: What is the horsepower of a 230v motor pulling 4 amps and having 82% efficiency?

HP V x I x Eff
        746
HP 230 x 4 x .82
        746
HP 754.4
        746
HP = 1 Hp
Eff = efficiency / HP = horsepower / V = volts / A = amps / PF = power factor

Horsepower Formulas
To Find Use Formula Example
Given Find Solution
HP HP = I X E X Eff.
746
240V, 20A, 85% Eff. HP HP = 240V x 20A x 85%
       746
HP=5.5
I I = HP x 746
     E X Eff x PF
10HP, 240V,
90% Eff., 88% PF
I = 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
         5252
HP = 1725 x 3.1
         5252
HP = 5347.5
         5252
HP = 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
              Np

rpmsyn = synchronous speed (in rpm)
f           = supply frequency in (cycles/sec)
Np       =  number of motor poles

Example: What is the synchronous speed of a four pole motor operating at 50 hz.?

rpmsyn = 120 x f
              Np
rpmsyn = 120 x 50
              4
rpmsyn = 6000
              4
rpmsyn = 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 Is

A. Ep = Es x Is
Ip
B. Ip = Es x Is
Ep
C. Is = Ep x Ip
Es
D. Es = Ep x Ip
Is

 


2. Voltage and Turns in Coil:
Voltage (p) x Turns (s) = Voltage (s) x Turns (p)
or Ep x Ts = Es x Ip

A. Ep = Es x Ip
Ts
B. Ts = Es x Tp
Ep
C. Tp = Ep x Ts
Es
D. Es = Ep x Ts
Tp

 

3. Amperes and Turns in Coil:
Amperes (p) x Turns (p) = Amperes (s) x Turns (s)
or Ip x Tp = Is x Ts

A. Ip = Is x Ts
Tp
B. Tp = Is x Ts
Ip
C. Ts = Ip x Tp
Is
D. Is = Ip x Tp
Ts

 


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-
power
90v 120v 180v 240v 500v 550v
Amperes
1/4 4.0 3.1 2.0 1.6
1/3 5.2 4.1 2.6 2.0
1/2 6.8 5.4 3.4 2.7
3/4 9.6 7.6 4.8 3.8
1 12.2 9.5 6.1 4.7
1-1/2 13.2 8.3 6.6
2 17 10.8 8.5
3 25 16 12.2
5 40 27 20
7-1/2 58 29 13.6 12.2
Horse-
power
90v 120v 180v 240v 500v 550v
Amperes
10 76 38 18 16
15 38 18 16
20 55 27 24
25 89 43 38
30 106 51 46
40 140 67 61
Horse-
power
90v 120v 180v 240v 500v 550v
Amperes
50 173 83 75
60 206 99 90
75 255 123 111
100 341 164 148
125 425 205 185
150 506 246 222
200 675 330 294

AC Single Phase Motors
Horse-
power
115v 200v 208v 230v
Amperes
1/6 4.4 2.5 2.4 2.2
1/4 5.8 3.3 3.2 2.9
1/3 7.2 4.1 4.0 3.6
1/2 9.8 5.6 5.4 4.9
3/4 13.8 7.9 7.6 6.9
1 16 9.2 8.8 8.0
1-1/2 20 11.5 11 10
2 24 13.8 13.2 12
3 34 19.6 18.7 17
5 56 32.2 30.8 28
7-1/2 80 46 44 40
10 100 57.5 55 50
Horse-
power
115v 200v 208v 230v

2 Phase (4 wire) AC Induction Type
Squirrel Cage and Wound Rotor
Horse-
power
115v 230v 460v 575v 2300v
Amperes
1/2 4.0 2.0 1.0 0.8
3/4 4.8 2.4 1.2 1.0
1 6.4 3.2 1.6 1.3
1-1/2 9.0 4.5 2.3 1.8
2 11.8 5.9 3.0 2.4
3 8.3 4.2 3.3
5 13.2 6.6 5.3
10 24 12 10
15 36 18 14
20 47 23 19
25 59 29 24
30 69 35 28
40 90 45 36
Horse-
power
115v 230v 460v 575v 2300v
Amperes
50 113 56 45
60 133 67 53 14
75 166 83 66 18
100 218 109 87 23
125 270 135 108 28
150 312 156 125 32
200 416 208 167 43

AC 3 Phase Induction Type Squirrel Cage and Wound Rotor
Horse-
power
115V 200V 208V 230V 460V 575V 2300V
Amperes
1/2 4.4 2.5 2.4 2.2 1.1 0.9
3/4 6.4 3.7 3.5 3.2 1.6 1.3
1 8.4 4.8 4.6 4.2 2.1 1.7
1-1/2 12.0 6.9 6.6 6.0 3.0 2.4
2 13.6 7.8 7.5 6.8 3.4 2.7
3 11.0 10.6 9.6 4.8 3.9
5 17.5 16.7 15.2 7.6 6.1
7-1/2 25.3 24.2 22 11 9
Horse-
power
115v 200v 208v 230v 460v 575v 2300v
10 32.2 30.8 28 14 11
15 48.3 46.2 42 21 17
20 62.1 59.4 54 27 22
25 78.2 74.8 68 34 27
30 92 88 80 40 32
40 120 114 104 52 41
Horse-
power
115v 200v 208v 230v 460v 575v 2300v
50 150 143 130 65 52
60 177 169 154 77 62 16
75 221 211 192 96 77 20
100 285 273 248 124 99 26
125 359 343 312 156 125 31
150 414 396 360 180 144 37
200 552 528 480 240 192 49
Horse-
power
115v 200v 208v 230v 460v 575v 2300v
Amperes
250 302 242 60
300 361 289 72
350 414 336 83
400 477 382 95
450 515 412 103
500 590 472 118

AC 3 Phase Synchronous Type Unity Power Factor
Horse-
power
230v 460v 575v 2300v
Amperes
25 53 26 21
30 63 32 26
40 83 41 33
50 104 52 42
60 123 61 49 12
75 155 78 62 15
100 202 101 81 20
125 253 126 101 25
150 302 151 121 30
200 400 201 161 40
Horse-
power
230v 460v 575v 2300v

Todo esta en ingles por que lamentablemente debemos acostumbrarnos a interpretar las tablas en este idioma por que fueron hechas para tal proposito de tratar de traducirlas seria cambiarlas mucho y esa no es la idea.