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What's the system total power factor?

What's the system total power factor?

What's the system total power factor?

(OP)
Hi,
I am trying to solve a power factor question but I ended up with a different answer.
The question is as shown below:


My Answer is:


However, the correct answer is C. That is the p.f. =0.857.



My question is where is my mistake?

Thanks.



RE: What's the system total power factor?

St(KVA)=10(KW) + 40/.8(KVA) = 60 KVA WRONG
KW and KVA are directed quantities and may not be added arithmetically.
Two other issues:
1. This should be in the Student Engineer General Discussion Forum.
This thread will soon disappear.
2. We don't do homework. I have shown you where your mistake is. From there it is up to you to work out the correct answer.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: What's the system total power factor?

VA of the resistor and VA of the other load would appear to be able to add since both are VA. But they can't because each VA is a vector going in a different direction.

I hate angle calculations when doing PF calculations. I always use PF = W/VA and pythagorean theorem.

RE: What's the system total power factor?

Quote (Lionel)

I hate angle calculations when doing PF calculations. I always use PF = W/VA and pythagorean theorem.
I feel the same way, Lionel.
At the Watts, add the VARs and use Pythagoras' theorem for the VA and then do PF.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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