How Do You Calculate Current and Power Factor in a Synchronous Induction Motor?

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Discussion Overview

The discussion revolves around calculating current and power factor in a synchronous induction motor, specifically focusing on a scenario involving a star-connected, three-phase motor under varying excitation conditions. Participants explore the implications of changes in generated emf and the resulting effects on current and power factor.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents a problem involving a synchronous induction motor, detailing the initial conditions including current, voltage, synchronous reactance, and the need to calculate generated emf and load angle.
  • The same participant expresses uncertainty about how to calculate current and power factor, referencing a specific formula.
  • Another participant confirms they have solved the problem, providing values for power factor and current but does not elaborate on the method used to arrive at these results.
  • Several participants express interest in understanding the method used to achieve the results, indicating a desire for clarification on the calculations involved.

Areas of Agreement / Disagreement

While one participant claims to have solved the problem, there is no consensus on the methodology used, and other participants seek further clarification on the calculations. The discussion remains unresolved regarding the specific steps taken to reach the stated results.

Contextual Notes

Participants have not provided detailed explanations of their calculations, and there is ambiguity regarding the assumptions made in the problem, particularly in relation to the effects of reduced excitation on the motor's performance.

Who May Find This Useful

Students and practitioners interested in electrical engineering, particularly those studying synchronous motors and power factor calculations, may find this discussion relevant.

zsolt2
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Homework Statement


A star-connected, three-phase synchronous induction motor takes a current of 10 amps from a 415 volt supply at unity power factor when supplying a steady load. If the synchronous reactance is 5 ohms/phase and the resistance is negligible, draw the phasor diagram and calculate the value of the generated emf and the load angle.
(ii) If the excitation is reduced by 10% and, as a consequence the generated e.m.f. is reduced by 10%, calculate the new value of the generated e.m.f E, the stator current, the power factor and the load angle, assuming that the load does not change.

Homework Equations


Voltage /phase:415 x Sqr3 =240 V
IXs= 10 x 5 = 50V[/B]

The Attempt at a Solution


i,
E^2=240^2 x 50^2=245V
cosσ=240/245=0.979 (σ=load angle)
σ=11.76°
ii,
E= 245-92454 x 0.1 =220.5
My problem is how to calculate the current and the power factor as I=P/(√3 x V x I x power factor)[/B]
 
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Hi zsolt2. I see that you have ticked to mark this thread as SOLVED.[/color]

Does this mean you have been able to answer the question, so don't need further help from anyone here?
 
Hi.
Yes I think I have solved it
P.f.=0.89
I= 11.24
If I am right
Thank you
 
zsolt2 said:
Hi.
Yes I think I have solved it
P.f.=0.89
I= 11.24
If I am right
Thank you
Love to know how you got that
 
The result is correct but I would like to know how you arrived at this result.
 

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