Solve 3 Phase Total Power Problems

[billyray]

Homework Statement

I have included the problems attached below. I have looked at a recent post and the equations made sense to me but I am very new to 3 phase systems basically know only what I have learned from trying to answer my questions. i feel my attempt is wrong from what I have seen online as total power equation in 3 phase system. I have included link. I am not sure which equation to use now I think mine is wrong.[/B]

Homework Equations

https://www.physicsforums.com/threads/delta-and-star-transformation-ac-circuits.791979/
and online 3 phase power solution
https://www.electricaltechnology.org/2014/09/delta-connection-power-voltage-current.html

The Attempt at a Solution

I have attached all my workings[/B]

 

[gneill]

Your calculations look okay to me. You might want to trim the significant figures in your final power value, maybe express it in kW.

 

[billyray]

hi gneill
thanks again.
Did you see the online link to P = √3 x VL x IL x CosФ for a balanced system delta. is that not different from mine.

 

[gneill]

Did you see the online link to P = √3 x VL x IL x CosФ for a balanced system delta. is that not different from mine.

Yes. Note that in this instance you have not calculated the Line currents ($I_L$), but rather the separate load branch currents for the Delta load. This makes a difference because the Line currents are made up of combinations of currents of load branches (which have different relative phases). Now, if you directly calculate the real power for each branch of the load as you've done, then you can simply sum those real powers.

 

[billyray]

thanks gneill