EECS 100 Spring Semester 1998 Practice Final Examination 3 Hours Closed Book Two 8 12 11 Sheets of Notes Allowed May 2 2003 1 30 minutes Refer to the circuit shown as Figure 1 a Write expressions for Kircho s Current Law at nodes X and Y b Make Thevenin Equivalents for the elements inside the dashed boxes A and B c Solve for voltages Vx and Vy d Find the power dissipated in the network as drawn in Fig 1 1 2 30 Minutes The circuit shown in Figure 2 is a parallel resonant LRC circuit with a resonant frequency f0 of 1 0 MHz a b c d Find the values of the components L and C in H and F Find the voltage appearing across the components at resonance Find the quality factor Q Find the frequencies at which the voltage across the components would be 3 0 dB from the voltage at resonance 3 30 minutes In the circuit shown as Fig 3 all four devices are nchannel MOSFETs with a value of k which is very large Logical 1 is 4 12 volts and the threshold voltage of the MOSFET transistors is 2 0 V Points A and B are considered inputs and X and Y are outputs a Find the relation between X and Y when A and B are at logic 0 b Find the logic values of X and Y when A 0 B 1 c Suppose that B 0 continuously but A brie y goes to logic 1 and then returns to zero what would X and Y be then d Name the speci c type of logic block that this circuit represents 2 4 30 minutes A load manager for PG E determines that his sector which includes Tracy and Manteca is drawing a total of 580 mega volt amperes MVA with an overall phase angle of ve degrees lagging However a commercial break is coming up on The Simpsons which causes customers to turn up their air conditioners a notch meaning an additional load of 70 MVA at thirty ve degrees lagging a Find the total load after the TV commercial active reactive and apparent power b Find the total current in each phase if the line voltage voltage between the phases is 380 kilovolt RMS and there are three phases c If the load manager were to switch in a synchronous capacitor to provide a minimum load for his sector what would the equivalent capacitance from each phase to ground be d What would the adjusted power be after this correction 5 30 Minutes An induction motor delivers 25 hp and runs with a real e ciency mechanical power out active power in of ninety four percent Speed is 1746 rpm Line voltage is 480 VRMS 3 and the phase angle is ten degrees lagging The three windings in the motor are deltaconnected a What is the slip s b Find the phasor current Im in each phase of the ac line Express in form I6 c Find the current in each of the delta connected phases d Find the total reactance X 0 e Find Rstator f Find the re ected rotor resistance at 100 slip R00 3 6 30 Minutes A synchronous machine is used to generate 60 Hz electrical energy into a resistive load The machine operates at 3600rpm The overall electrical demand is 800 megawatts at zero phase The ux product in each phase provided by the rotor N 0 is 10 0 Weber and the phases are wye connected The power angle is 30 degrees a Find the rms line voltage the voltage between the phases b How many poles does this machine have c What is the value of the reactance Xs in each phase d Find the excitation voltage e Draw a phasor diagram labeling the stator current the stator reaction and the excitation e and the output voltage all referenced to ground for one phase 4
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