Exam 1 - Solution - ELEN3441FundamentalsofPowerEngineering...

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ELEN 3441 – Fundamentals of Power Engineering Spring 2011 Exam 1: Solutions 1. (5 pt.) How would you determine a power factor if the apparent and reactive powers are given? 22 cos SQ P PF SS θ = = 2. (5 pt.) What is the saturation of ferromagnetic core? Saturation is the state of ferromagnetic core when further increase in the external magnetic field (mmf) leads to a marginal or no increase in the magnetic flux through the core. 3. (5 pt.) What is the purpose of “per-phase circuits”? Per-phase circuits are used to simplify the analysis of three-phase circuits. 4. (10 pt.) Ferromagnetic cores are frequently made laminated. What is the main advantage of this design? Core lamination helps reducing paths that eddy currents travel through the core and, therefore, reduce the associated eddy current losses. 5. (10 pt.) What are two disadvantages of Y-Y connection of three-phase transformers? 1) Slight unbalance in the load may severely unbalance the system; 2) Third harmonic current is possible.
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This note was uploaded on 09/21/2011 for the course EE ee taught by Professor Ee during the Spring '10 term at Istanbul Technical University.

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Exam 1 - Solution - ELEN3441FundamentalsofPowerEngineering...

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