Question

A balanced three-phase 208 V wye-connected source supplies a balanced three-phase wyeconnected load. If the line current IA is measured to be 20 A and is in phase with the line-to-line voltage VBC, find the per-phase impedance of the load

Answer 1

Answer:

6.004 Ω

Explanation:

For  a Y- connected system given that :

Line voltage, $V_L = 208 \ V$

Line current , $I_L=20\ A$

and specified that $V_L \ and \ I_L$ are in phase.

Hence the impedance will be pure resistive.

For Y-system

$V_L = \sqrt3 V_{ph}$

$V_{ph}$ = phase voltage

$V_{ph}$ $=\frac{V_L}{\sqrt3} = \frac{208}{\sqrt3}$

    = 120.08 V

Line current = Phase current

$I_L = I_{ph} = 20 \ A$

Now, $z_{ph} = \frac{V_{ph}}{I_{ph}}=\frac{120.08}{20}$

                          = 6.004 Ω