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Phasor diagram help

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Cassy85

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Hi, I'm struggling with question 2b.
Any help would be appreciated.
Thanks in advance.

This is what I have got for question 2a.

  1. Calculate phase current
Phase current = 250003 x 415 x 0.8

Phase current = 25.1 Amps

cos-10.8=36.87

I = 25.1 ∠36.87° Amps

  1. Calculate the stator reactive voltage drop IXs

Voltage drop = IaXs



25.1 x 4 ∠36.87° + 90°


Voltage drop (IXs) = 100.4 ∠126.87° volts
 

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your notation leaves something to be desired.
always write down the units. what you do with the values, do with the units
if the resulting units are incorrect, you made a mistake somewhere

you did not multiply the power, 3 for phases, voltage and power factor
you divided them:
power per phase = 25000 W / 3 = 8333.33 W
phase current = 8333.33 W / 415 V / 0.8 = 25.1 A

as for the angle, cos^-1 (0.8) = 36.87 degrees or arccos(0.8) = 36.87 degrees

use divide (/) for divide, and multiply (x) for multiply and ^ for exponents

as for the phasor diagram, the phase voltage is 415V at 0 degrees
you calculated the phase current at 25.1 A at 36.87 degrees
you calculated the stator drop as 100.4 V at 126.87 degrees

they are phasors, not vectors, but is you draw them like vectors,
you should be through b i, and need only connect E between the appropriate phasors to get ii
for iii, either measure or calculate E - like i said, they are phasors, not vectors, but the calculation is the same
likewise for iv
 
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