hw2_solution

hw2_solution - EE 459 HW SET #2 Chapter2: (Summary...

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EE 459 HW SET #2 Chapter2: (Summary questions for insights) Q1: What are the reasons behind using the three-phase systems instead of the single- phase systems? A: The three-phase systems have the following advantages over the single-phase systems: The instantaneous real power of the balanced three-phase systems is a constant. Since fuel consumption is directly linked to real power generation, it implies the generating machines are consuming fuels at a constant rate to generate a constant real power output. Such machines are much easier to design and operate than machines that have time-varying fuel consumptions. The balanced three-phase systems do not need a return wire since their neutral-to- neutral voltage difference is zero. Accordingly, we can save 50% of the wires comparing to three single-phase systems that carry the same loads as the three- phase systems. Even for slightly unbalanced systems, the return wire can be much smaller due to low voltage potentials between neutrals. Less wire usage implies that less power loss will occur on the connecting wires. Q2: Why some countries would like to impose requirements on the power factors for the loads? A: A typical requirement on the load is that its power factor has to be close to one, say,
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This note was uploaded on 06/29/2010 for the course ECEN 459 taught by Professor Staff during the Spring '08 term at Texas A&M.

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hw2_solution - EE 459 HW SET #2 Chapter2: (Summary...

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