Essential Formulas for Motor Engineering
Motor Engineering is a vital part of the Engineering sector. There is no industry where a motor is not used; from utility to machinery keeping it running is mandatory.
Due to the use of huge motors, a large portion of everyday work time also consumed this fellow; and need to face new and critical problems every time.
Yes, friends, to solve problems sometimes a quick and short-cut formula is very effective. That is the main reason today's presentation is on a very easy and basic formula related to motors which we call an Essential Formula for Motor engineering.
We know, You who are engaged with motor engineering know these formulas very well, but sometimes memory is lost. Hope this will help like a friend.
Ohm's Law in Ectricity
Ohm's Law is the very basic formula for electrical engineering. Everybody knows this formula, here all of this formula is in a circle for easy understanding.
Three Phase Values
Just memories the value 1.732 which comes from the square root of 3; multiply with this value to get three values from a single phase. Follow the following table for some common 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
415 volts x 1.732
|
use
719
|
For
440 volts x 1.732
|
use
762
|
For
460 volts x 1.732
|
use
797
|
For
480 volts x 1.732
|
use
831
|
AC/DC Formulas
Horse Power, Kilowatts, KVA related some formula for AC-Alternating Current and DC- Direct Current when one term is known and other terms need to fiend out.
To
Find
|
Direct
Current
|
AC 1 phase
|
AC
3 phase
|
Amps when
Horsepower is Known
|
HP
x 746
E
x Eff
|
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
1.73 x E x PF
|
Amps when
kVA is known
|
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 1.73 x PF
1000
|
Kilovolt-Amps
|
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 1.73 x PF
746
|
AC Efficiency and Power Factor Formulas
We need some formula to fiend out Motor Efficiency and Power factor for single phase or three phase motors. Follow the following table formula.
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 PF x 1.732
|
Motor Application Formulas
There are four formulas related to motor horsepower, kilowatts, torque in pound-foot, or newton-meter. These formulae we are calling the Motor Application Formula.
Horsepower = Torque (lb-ft) x RPM
5252
|
Kilowatts = Torque
(N-m) x RPM
9550
|
Torque (lb-ft) = Horsepower x 5252
RPM
|
Torque (N-m) = Kilowatts x 9550
RPM
|
IEC-Style Contactors and Starters Selection Guide:
Average Amperage for Given Horsepower Motor Ratings
The
table below provides the average full-load currents of squirrel cage motors
based on NEC (National Electrical Code) Tables 430-148, 149, and 150.
These
values are given only as a guide - they may vary depending on the type of motor
and manufacturer. Refer to the actual motor nameplate for full-load current
values.
HP
|
110 to 120 VAC
|
220 to 240 VAC
|
440 to 480 VAC
|
||||||
Single
Phase
|
Two
Phase
|
Three
Phase
|
Single
Phase
|
Two
Phase
|
Three
Phase
|
Single
Phase
|
Two
Phase
|
Three
Phase
|
|
1/10
|
3.0
|
-
|
-
|
1.5
|
-
|
-
|
-
|
-
|
-
|
1/8
|
3.8
|
-
|
-
|
1.9
|
-
|
-
|
-
|
-
|
-
|
1/6
|
4.4
|
-
|
-
|
2.2
|
-
|
-
|
-
|
-
|
-
|
1/4
|
5.8
|
-
|
-
|
2.9
|
-
|
-
|
-
|
-
|
-
|
1/3
|
7.2
|
-
|
-
|
3.6
|
-
|
-
|
-
|
-
|
-
|
1/2
|
9.8
|
4.0
|
4.4
|
4.9
|
2.0
|
2.2
|
2.5
|
1.0
|
1.1
|
3/4
|
13.8
|
4.8
|
6.4
|
6.9
|
2.4
|
3.2
|
3.5
|
1.2
|
1.6
|
1
|
16.0
|
6.4
|
8.4
|
8.0
|
3.2
|
4.2
|
4.0
|
1.6
|
2.1
|
1 1/2
|
20.0
|
9.0
|
12.0
|
10.0
|
4.5
|
6.0
|
5.0
|
2.3
|
3.0
|
2
|
24.0
|
11.8
|
13.6
|
12.0
|
5.9
|
6.8
|
6.0
|
3.0
|
3.4
|
3
|
34.0
|
16.6
|
19.2
|
17.0
|
8.3
|
9.6
|
8.5
|
4.2
|
4.8
|
5
|
56.0
|
26.4
|
30.4
|
28.0
|
13.2
|
15.2
|
14.0
|
6.6
|
7.6
|
7 1/2
|
80.0
|
38.0
|
44.0
|
40.0
|
19.0
|
22.0
|
21.0
|
9.0
|
11.0
|
10
|
100.0
|
48.0
|
56.0
|
50.0
|
24.0
|
28.0
|
26.0
|
12.0
|
14.0
|
15
|
135.0
|
72.0
|
84.0
|
68.0
|
36.0
|
42.0
|
34.0
|
18.0
|
21.0
|
20
|
-
|
94.0
|
108.0
|
88.0
|
47.0
|
54.0
|
44.0
|
23.0
|
27.0
|
25
|
-
|
118.0
|
136.0
|
110.0
|
59.0
|
68.0
|
55.0
|
29.0
|
34.0
|
30
|
-
|
138.0
|
160.0
|
136.0
|
69.0
|
80.0
|
68.0
|
35.0
|
40.0
|
40
|
-
|
180.0
|
208.0
|
176.0
|
90.0
|
104.0
|
88.0
|
45.0
|
52.0
|
50
|
-
|
226.0
|
260.0
|
216.0
|
113.0
|
130.0
|
108.0
|
56.0
|
65.0
|
60
|
-
|
-
|
-
|
-
|
133.0
|
154.0
|
-
|
67.0
|
77.0
|
75
|
-
|
-
|
-
|
-
|
166.0
|
192.0
|
-
|
83.0
|
96.0
|
100
|
-
|
218.0
|
248.0
|
-
|
109.0
|
124.0
|
|||
125
|
-
|
-
|
-
|
-
|
-
|
312.0
|
-
|
135.0
|
156.0
|
150
|
-
|
-
|
-
|
-
|
-
|
360.0
|
-
|
156.0
|
180.0
|
200
|
-
|
-
|
-
|
-
|
-
|
480.0
|
-
|
208.0
|
240.0
|
250
|
-
|
-
|
-
|
-
|
-
|
602.0
|
-
|
-
|
302.0
|
300
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
361.0
|
350
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
414.0
|
400
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
477.0
|
500
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
590.0
|
No comments:
Post a Comment
WAZIPOINT:
Thank you very much to visit and valuable comments on this blog post. Keep in touch for next and new article. Share your friends and well-wisher, share your idea to worldwide.