Figure 12-17 A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions:
-IL(Alt) = ____ A.
A) 78.22
B) 81.20
C) 103.92
D) 107.88

Question

Figure 12-17  A wye-connected three-phase alternator supplies power to a delta-connected resistive load. The alternator has a line voltage of 480 V. Each resistor of the delta load has 8 ohms of resistance. Find the values in the following questions:
-IL(Alt) = ____ A.
A) 78.22 
B) 81.20 
C) 103.92 
D) 107.88

Quizplus · Accepted Answer

To find IL(Alt), we first need to find the line current in the delta load. We can do this using Ohm's Law: 
I(R) = V(R) / R
I(R) = 480V / 8Ω
I(R) = 60A

Since the delta load is connected to the alternator in a wye configuration, we can use the line-to-phase voltage relationship to find the line current in the alternator: 
VL = √3*VP 
VP = VL / √3 
VP = 480V / √3 
VP = 277.1V

Now we can use the power relationship between the alternator and load: 
P(Alt) = P(R) 
VL(IL(Alt)) = VP(IL(R)) 
IL(Alt) = IL(R) * √3 * VP / VL 
IL(Alt) = 60A * √3 * 277.1V / 480V 
IL(Alt) = 103.92A

Therefore, the answer is choice C.

Figure 12-17 a Wye-Connected Three-Phase Alternator Supplies Power to a Delta-Connected