Electric Machines: Syncronous generator drivng var. load connected to induction motor


by VinnyCee
Tags: electric machines, induction machine, power electronics, pwm, synchronous machine
VinnyCee
VinnyCee is offline
#1
May1-11, 04:14 PM
P: 492
1. The problem statement, all variables and given/known data



A Y-connected synchronous generator with a wound field is used to provide pure sinusoidal voltage of 240V, 50Hz, to a variable electrical load. The generator is powered from an induction motor, fed fropm a DC source of 600V through a PWM inverter.

Induction motor ratings: 4 poles, Y connected, 240V, 60Hz, [tex]L_{ls}\,=\,L_{{lr}\,=\,3.2\,mH[/tex], [tex]L_m\,=\,40\,mH[/tex], [tex]R_S\,=\,0.15\,\Omega[/tex], [tex]R_r\,=\,0.3\,\Omega[/tex].

Synchronous generator ratings: Y connected, 4 poles, 240V line to line, [tex]X_m\,=\,19\,\Omega[/tex], [itex]k\,=\,\frac{I_F}{i_f}\,=\,2.1\,Vs[/itex].

For load of the generator, P=3kW at p.f. = 0.85 lagging. Calculate the following:

1) The field of the generator.

2) The torque of the induction machine.

3) The voltage of the induction machine.

4) The current on the DC side of the inverter.



2. Relevant equations

[tex]\left(V_L\right)_{avg}\,=\,(2D\,-\,1)\,V_0[/tex]



3. The attempt at a solution

I've no idea how to even start this problem! It's supposed to be an exam question, but I can't even start it using all notes and the text! Been thinking about it for about 12 hours now, I'm certainly stuck:(

The duty cycle (D) is not given so I can't even get what voltage the PWM inverter outputs.
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