Kaplan Sample Exam #7

[Machiavelli999]

I know this sample exam is full of errors, so this could just be another error, but on Problem #7, they say it is an unbalanced load and give currents for Ib and Ic only. Then to find Ia (in order to find the power in Phase A) Kaplan just does KCL around the N (neutral) point. Ia + Ib + Ic = 0.

But how could they do this?? If it is an unbalanced load, there must be an In (Neutral Current). Is this a mistake or am I wrong here?

Thanks.

 

[cableguy]

This one is correct.

There is no path to ground for neutral current on the diagram. The connection is 3-wire only (no neutral conductor).

I like Wattmeter problems, but you really really have to watch the phase rotation and phasor diagram on them.

Note that this is another problem where they gave us a floating "N" on the far left side of the diagram, and a little "n" in the circuit. They set reference at VAN, and not VAn.