Problem 1:Consider a 75kVA, 7500/480V, 60 Hz distribution transformer and following test
data: O/C...

Question

Problem 1:Consider a 75kVA, 7500/480V, 60 Hz distribution transformer and following test
data: O/C Test (on Primary) – VOC = 7500V, IOC = 0.35 A, POC = 473 W and S/C Test (on
Primary) – VSC = 499V, ISC = 10A and PSC = 1050 W. Determine the following:
a) The value of the load impedance connected to the low-voltage side that will cause the
transformer to be fully loaded
b) The value of such a load impedance referred to the high-voltage side
c) The values of the load current referred to the low-voltage and high-voltage sides
d) Write a MATLAB program to calculate all quantities and compare your hand calculation

David · Accepted Answer

Problem 1 
 
Consider a 75kVA, 7500/480V, 60 Hz distribution transformer and following test data:  
O/C Test (on Primary) – VOC = 7500V, IOC = 0.35 A, POC = 473 W 
S/C Test (on Primary) – VSC = 499V, ISC = 10A and PSC = 1050 W 
Determine the following:  
a) The value of the load impedance connected to the low-voltage side that will cause the 
transformer to be fully loaded 
b) The value of such a load impedance referred to the high-voltage side 
c) The values of the load current referred to the low-voltage and high-voltage sides 
d) Write a MATLAB program to calculate all quantities and compare your hand calculation 
 
 
Solution 1 
 
Considering a single phase distribution transformer, 
 
Turns ratio, K = 480/7500 = 0.064 
 
From the short circuit test data, the total impedance of the circuit referred to HV side is, 
 9.49
10
499
01
SC
SC
I
V
Z  
 
The rated secondary (LV side) load current is, 
A
V
KVA
I
Rated
Rated 25.156
480
75000
_2
2    
 
Thus,

Problem 1: Consider a 75kVA, 7500/480V, 60 Hz distribution transformer and following test data: O/C Test (on Primary) – VOC = 7500V, IOC = 0.35 A, POC = 473 W and S/C Test (on Primary) – VSC = 499V,...

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