Efficiency (%) 110 100 90 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 70 80 90 100 110 Motor Loading (%) The relationship between % of full load for each motor and power factor (they are all the same) is given by the graph below: 0.8 0.7 pf (lagging) 0.6 0.5 0.4 G Ş 3 * སྟྲ ཊྛ ° 0.3 0.2 0 0 20 40 60 80 100 120 Motor Loading (%) a) What is the minimum required transformer rating in kVA? b) By what percentage could the required transformer rating be reduced if a capacitor bank were installed in parallel with the motors, improving the power factor of the loadcentre to unity? Problem 4: Question 1. Consider the three-phase loadcentre shown below: 27.9 kVRMS 400 VRMS M M M Motor 2 80 hp Motor 3 80 hp Motor 1 80 hp Each motor is rated at 80 hp but is only loaded mechanically as follows: Motor # % Loading 1 40 2 50 3 70 The relationship between % of full load for each motor and efficiency (they are all the same) is given by the graph below:
Efficiency (%) 110 100 90 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 70 80 90 100 110 Motor Loading (%) The relationship between % of full load for each motor and power factor (they are all the same) is given by the graph below: 0.8 0.7 pf (lagging) 0.6 0.5 0.4 G Ş 3 * སྟྲ ཊྛ ° 0.3 0.2 0 0 20 40 60 80 100 120 Motor Loading (%) a) What is the minimum required transformer rating in kVA? b) By what percentage could the required transformer rating be reduced if a capacitor bank were installed in parallel with the motors, improving the power factor of the loadcentre to unity? Problem 4: Question 1. Consider the three-phase loadcentre shown below: 27.9 kVRMS 400 VRMS M M M Motor 2 80 hp Motor 3 80 hp Motor 1 80 hp Each motor is rated at 80 hp but is only loaded mechanically as follows: Motor # % Loading 1 40 2 50 3 70 The relationship between % of full load for each motor and efficiency (they are all the same) is given by the graph below:
Introductory Circuit Analysis (13th Edition)
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ISBN:9780133923605
Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
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Transcribed Image Text:Efficiency (%)
110
100
90
80
70
60
50
40
30
20
10
0
0 10 20 30
40 50 60 70 80 90 100 110
Motor Loading (%)
The relationship between % of full load for each motor and power factor (they are
all the same) is given by the graph below:
0.8
0.7
pf (lagging)
0.6
0.5
0.4
G Ş 3 * སྟྲ ཊྛ °
0.3
0.2
0
0
20
40
60
80
100
120
Motor Loading (%)
a) What is the minimum required transformer rating in kVA?
b) By what percentage could the required transformer rating be reduced if a
capacitor bank were installed in parallel with the motors, improving the power
factor of the loadcentre to unity?
Transcribed Image Text:Problem 4: Question
1. Consider the three-phase loadcentre shown below:
27.9 kVRMS
400 VRMS
M
M
M
Motor 2
80 hp
Motor 3
80 hp
Motor 1
80 hp
Each motor is rated at 80 hp but is only loaded mechanically as follows:
Motor #
% Loading
1
40
2
50
3
70
The relationship between % of full load for each motor and efficiency (they are all
the same) is given by the graph below:
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