Applying Thevenin's theorem to AC circuits

Click For Summary

Discussion Overview

The discussion revolves around the application of Thevenin's theorem to AC circuits, specifically addressing issues related to phase angles and power factors. Participants are exploring the implications of their calculations and interpretations of circuit behavior.

Discussion Character

  • Debate/contested, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant expresses confusion over their results compared to previous threads and questions the validity of their calculations, particularly regarding current angles.
  • Another participant points out a potential error in the sign of the imaginary part of a load, suggesting that it may be incorrect.
  • A participant questions the relationship between lagging power factors and phase angles, asserting that a lagging power factor should correspond to a negative phase angle and thus a negative imaginary component.
  • Responses challenge this assertion, indicating that the understanding of lagging and leading power factors may be misinterpreted.
  • One participant acknowledges their misunderstanding and reflects on the confusion between the angle of current and voltage.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of phase angles and power factors, with multiple competing views and some confusion remaining in the discussion.

Contextual Notes

There are unresolved assumptions regarding the definitions of phase angles and their implications for circuit analysis, as well as the specific context of the calculations being discussed.

mpar3
Messages
6
Reaction score
1
Homework Statement
FIGURE 1 shows a 50 Ω load being fed from two voltage sources via
their associated reactances. Determine the current i flowing in the load by:

(a) applying Thévenin’s theorem
(b) applying the superposition theorem
Relevant Equations
Thevenin equivalents, polar & rectangular conversions
1634574980465.png


Image.jpg
Image (2).jpg

So I've seen other threads on here with the same problem from a few years ago, and I'm just not getting the same answers. However, I followed along with a similar problem in the textbook and used all the same methods, so can't understand where I've gone wrong, or if I even am wrong. Also not sure if its ok that the current should be at an angle greater than 90 degrees
 
  • Like
Likes   Reactions: arhzz
Physics news on Phys.org
The Electrician said:
See the first few posts in this thread: https://www.physicsforums.com/threads/thevenins-theorem.775385/

You have the sign of the imaginary part of the 50 Ω load wrong.
I thought a lagging power factor leads to a negative phase angle, and thus a negative imaginary component. Is that not right?
 
  • Like
Likes   Reactions: mpar3
The Electrician said:
That is not right.
Look here: https://en.wikipedia.org/wiki/Power_factor#Lagging_and_leading_power_factors

Part way down the page under the heading "Lagging and leading power factors" you'll find discussion of the topic.
I don't know why I was so set on it being negative. I think I must have mixed it up with the angle between current and voltage maybe. Thanks for your help
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 17 ·
Replies
17
Views
3K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 28 ·
Replies
28
Views
7K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 9 ·
Replies
9
Views
6K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 18 ·
Replies
18
Views
3K