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Quick question on 3 phase before my final

  • Thread starter tanky322
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Quick question on 3 phase before my final!!

1. Homework Statement

In equations for 3 phase power there is an angle that is mentioned, but I dont know if this is the angle of the impedance or another angle. Im a little confused. The equations are below.



2. Homework Equations
P=(VrmsIrms)cos([tex]\theta[/tex])
Q=(VrmsIrms)sin([tex]\theta[/tex])


Any help?
 

Answers and Replies

PhanthomJay
Science Advisor
Homework Helper
Gold Member
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1. Homework Statement

In equations for 3 phase power there is an angle that is mentioned, but I dont know if this is the angle of the impedance or another angle. Im a little confused. The equations are below.



2. Homework Equations
P=(VrmsIrms)cos([tex]\theta[/tex])
Q=(VrmsIrms)sin([tex]\theta[/tex])


Any help?
I'm certainly not an electrical expert, but the angle you are referring to is the phase angle betwen the voltage and the current, where [tex]cos\theta = power factor[/tex]. For purely resistive loads, theta is 0, hence the power factor is unity, and there is no reactive power Q. However, I don't quite understand your equation, since typically ,for power transmsission, [tex] P= \sqrt3(V)(I)cos\theta [/tex]. That's about it for my electrical knowledge.
 

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