# Verifying homework

Discussion in 'Homework Help' started by EL7819, Apr 17, 2011.

1. ### EL7819 Thread Starter New Member

Apr 15, 2011
20
0
Hello,
I wanted to know If Im doing this question correctly?

1.)A voltmeter, a PF meter, and a wattmeter are connected to a balanced 3 phase, 4 wire load. The Readings are 1500 Watt, 0.50 PF, 120 Volts. What current flows?

This is my understanding so far: There are 3 branches and 1 neutral branch to the transformer. If it is balanced then each branch excluding the neutral, has 500 Watts.

(120Volts)(0.50PF)(3)=500Watts---------> 180=500Watts/180= I=8.33A

Or I worked it out this way too..

(120Volts)(0.50PF)(SqRt3)=1500Watts

60*1.732=1500Watts

103.92=1500W/103.92=14.43A These both are two choices that are answers listed to the problem. Im having trouble understanding using the square root of 3, or multiplying with 3 for 3 phase systems. Are there any resources that will help me understand this better? I think it would be the 1st way but I'm not sure. Any help is greatly appreciated.
Thank you.

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
789
Either answer could be correct depending on whether the stated voltage of 120V is the line-to-line voltage or the line-to-neutral voltage. The question doesn't make that clear, although it is more likely to be the latter. In that case 8.33A would be the correct answer.

Apr 15, 2011
20
0
Thank you.