Complex Power, calc load impedance

Click For Summary

Discussion Overview

The discussion revolves around calculating the load impedance given a specific real power absorption and power factor. Participants explore the relationships between apparent power, real power, and impedance, while addressing the definitions and units involved in the calculations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant assumes that the given power of 58959W is apparent power (S) and attempts to calculate impedance using this assumption.
  • Another participant clarifies that apparent power is typically expressed in VA, while real power is in W and reactive power in VAR.
  • A subsequent reply reaffirms the use of the equation for average power, suggesting that the impedance calculation leads to an extremely high resistance value.
  • Another participant notes that impedance should be expressed as a complex number or in magnitude and angle form, indicating a misunderstanding in the initial approach.
  • A participant acknowledges their error in input and expresses gratitude for the clarification provided.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct approach to calculating impedance, as there are multiple interpretations of the power values and their implications for the calculations.

Contextual Notes

There is a lack of clarity regarding the definitions of apparent power versus real power, and the implications of the power factor on the calculations. The discussion also highlights potential misunderstandings about how to express impedance.

Zarathuztra
Messages
36
Reaction score
0

Homework Statement



A load absorbs 58959W at a lagging power factor of pf = 0.73. If the current flowing through the load is ix = 0.001A-rms , determine the impedance of the load.

Homework Equations



Ohms law
Impedance/Voltage/Power Triangles

The Attempt at a Solution


If the load absorbs 58959W, I'm assuming that is apparent power (S)

If 58959W is S then by Pavg = S*pf = Irms2R

R = 58959*.73/.0012 = 43.04 GΩ (must be wrong...)

I would then take R/pf = Z... but the number gets more ridiculous. How am I going about this wrong?
 
Physics news on Phys.org
Apparent power is usually specified in VA rather than W. Real power is given in W, reactive power in VAR.
 
then 58959 = Pavg

and Pavg = irms2 * R

so 58959/.0012 = R = 5.9 * 1010

Z = R/pf = 5.9 * 1010 / 0.73
 
Okay, but usually an impedance is specified by its real and reactive components (it's actually a complex number), or in magnitude and angle form.
 
ah that's what was wrong with my input.. lol. Thanks gneill
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 18 ·
Replies
18
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 6 ·
Replies
6
Views
4K
Replies
2
Views
3K