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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°

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]