Transcript Problem #2-8

Problem #2-8
• A 480 – 120 V, 60 Hz transformer has its high
voltage winding connected to a 460 V system,
and its low voltage winding connected to a
24/32.8°Ω load. Assume that the transformer is
ideal. Determine
–
–
–
–
–
the secondary voltage
the secondary current
the primary current
the input impedance at the primary terminals
the active, reactive, and apparent power drawn by the
load
The secondary voltage
480
4
120
E p 460V
Es 

 115V
a
4
a
The secondary current
Es  I s Z load
Es
1150
Is 

 4.79  32.8 A
Z load 2432.8
The primary current
Is
I s  aI p  I p 
a
4.79  32.8
Ip 
 1.2  32.8
4
The input Impedance at the primary terminals
Z in'  a 2 Z load  (4) 2 (2432.8)
Z  38432.8
'
in
The active, reactive, and apparent power drawn by the load
S  Vs I s*  (115V )( 4.7932.8 A)  550.8532.8VA
P  Vs I s cos  load  (115V )( 4.79 A)(cos 32.8)
P  462.7W
Q  Vs I s sin  load  (115V )( 4.79 A)(sin 32.8)
Q  298.56VARS