Current Angle More Than Ninety Degrees

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Discussion Overview

The discussion revolves around the calculation of power factor for a current in a synchronous generator, specifically when the current angle exceeds 90 degrees. Participants explore the implications of phase angles in relation to terminal voltage and the nature of capacitive versus inductive loads.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant presents a current Ia with an angle of -159.9 degrees and questions how to calculate the power factor, suggesting that the book's value of 23.13 degrees may come from subtracting the current angle from 180 degrees.
  • Another participant introduces the concept of capacitive versus inductive loads, indicating a need to understand the implications of phase angles greater than 90 degrees.
  • A different participant expresses confusion about the meaning of an angle greater than 90 degrees, noting their mathematical interpretation of the current angle as 159 degrees and its conversion to a negative phase angle.
  • One participant challenges the necessity of the 159-degree angle, emphasizing the book's statement that the current leads the terminal voltage by 23.13 degrees and referencing a tutorial on phase relationships in circuits.
  • Another participant provides a calculation for the phase angle in a synchronous alternator context, indicating the use of specific values for E, V, and X.
  • A later reply suggests that the discussion may be better suited for the Homework forum, indicating a lack of progress in resolving the questions posed.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of phase angles, with some supporting the book's assertion about the leading current and others questioning the validity of the 159-degree angle. The discussion remains unresolved regarding the implications of angles greater than 90 degrees.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about phase relationships, the definitions of leading and lagging, and the specific context of the calculations provided. Some mathematical steps and their implications remain unresolved.

jaus tail
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Hi,
I'm studying Sync Generators. In one problem I got Ia as 1.59 angle of -159.9 degrees.

How do you calculate power factor for such a current?
Book says Ia leads Terminal Voltage by 23.13 degrees.
I guess they got that value by 180 - 159.9
But why?
 
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Capacitive load versus Inductive load.
 
But in capacitive and inductive the phase angle is from 0 to 90 degrees.
I'm not able to understand what does angle more than 90 mean.

Mathematically i used 159 degrees by
I angle 159
= I cos 159 + j I sin 159
and that equals I angle -23
 
I fail to see a reason for 159 degrees. The phase angle has already been given:
jaus tail said:
Book says Ia leads Terminal Voltage by 23.13 degrees.
Pay attention to the book quote above as to which is leading, Voltage or Current, and to the fourth and fifth sentences in this tutorial. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/phase.html

It is customary to use the angle by which the voltage leads the current. This leads to a positive phase for inductive circuits since current lags the voltage in an inductive circuit.[i/]
 
I got the phase angle as 159 degrees. In sync alternator I = (E - V)/X
E is 2.341 pu angle + 90
V = 1 angle 0
X = j1.6
 
Sorry we are not making progress. Your problem can likely be better answered in the Homework forum. Be sure to fill in the information in the template there so people here get a better idea of the question details.

Paging @russ_watters to assist in this redirection.
 
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