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ee341_h04_Wi2012 - line-line voltages Wye Delta Line...

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ECE 341 Homework #4 Due: Fri. 24 Feb. 12 Problem 1 : A three-phase eight-pole has a 24-slot stator. There are 30 turns of wire in each pair of slots. And all the 30 turns are connected in series. All coils in each phase are connected in series, and the three phases are connected in wye connection. The flux per pole in the machine is 0.060 Wb, and the speed of rotation of the magnetic field is 3600 r/min. (a) What is the frequency of the voltage produced in this winding? (2 pts.) (b) What are the resulting phase voltage of this stator? (2 pts.) Problem 2 : (5.1) from the text book. (2 pts.) Problem 3: (6.2 a, c) from the text book (6 pts.) Problem 4: The following figure shows a power system consisting of a three-phase generator supplying one load through a transmission line with a pair of ideal three-phase transformers. The voltage from the three phase generator is 480 V. The base powers and voltages are identified in the picture. ( Note : The numbers for voltages are RMS values of
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Unformatted text preview: line-line voltages.) Wye Delta Line impedance: 1+j1 ohm Vbase1=480 V Vbase2=100,000 V Three phase wye-delta transformer Delta Wye Three phase delta-wye transformer Load 0.082+j0.082 ohm Vbase3=480 V Sbase2=2000 kVA Sbase1=2000 kVA Sbase2=2000 kVA Three phase generator 1) Calculate the per-unit values of the line impedance, load impedance, and load end voltage; (2 pts.) 2) Sketch the per-phase per-unit equivalent circuit of this power system; (1 pts.) 3) Calculate the power factor of the system; (1 pts.) 4) Calculate the efficiency of the system; (2 pts.) 5) If you are asked to increase the load side power factor to 1 by adding an additional component in parallel with the existing load in the circuit you sketched in 2), what component would it be? a) Sketch your new circuit; and b) Show the calculations of the value of the additional component. (2 pts.) Assume the system frequency is 60 Hz ....
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