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Calculation of Electrical Quantities in Three Phase Circuits using MATLAB

Khalid S. Al-Olimat, Pete Jankovsky, Matt Valerio and Jack Skinner Ohio Northern University

Abstract

This paper presents a MATLAB program that utilizes a Graphical User Interface (GUI) to calculate the electrical quantities of three phase circuits. The GUI is designed in a way to allow the user to enter the resistances and reactances of the source, the transmission line and that of the load respectively. It also requires a voltage value of one of the phases at the generator end. This program performs the calculations with respect to the specified connection type. There are four types: wye-wye, wye-delta, delta-wye and delta-delta. This allows the students to compare the obtained results and can check the validity of their solutions of homework problems involving three phase circuits in electric circuits, energy conversion and power systems courses.

Introduction

When considering ac steady-state circuits and their relation to electric power generation and transmission, we are dealing with what is known as polyphase circuits, or more specifically three-phase circuits. It is not only more economical to transmit electric power through three- phase circuits, but also power transmission is more efficiently accomplished at such high voltages. In addition, it is possible to obtain much more power from fewer components with a three-phase circuit as well as having the ability to deliver a constant amount of power to the load at all times.

Students usually have difficulties in applying the concepts in three phase circuits due to the different configurations of such circuits. There are four different configurations, Y-Y, Y-Delta, Delta-Y and Delta-Delta. The difficulty results from the fact that three phase circuits are alternating current circuits which their calculations deal with complex numbers. When dealing with complex numbers, there are two formats, rectangular and polar. Usually it is easier to deal with polar form since it gives the magnitude and the phase angle of voltages and currents involved in such systems. In addition, there are many terms involved regarding current, voltage and power. These are phase current, line current, phase voltage, line voltage, apparent power per phase, real power per phase, reactive power per phase, total apparent power, total real power and total reactive power.

There are many software packages available to analyze electric and electronic circuits. The most popular packages are PSPICE and WORKBENCH. These packages require students to draw the circuit to be analyzed then it will be simulated and give the students the results based on the desired analysis and set up. Using such software packages is an excellent practice, but the problem with those they don’t show students the intermediate steps or how they went about to solve for the requirements. When students compare their solutions with the obtained results

Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition Copyright  2005, American Society for Engineering Education

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Jankovsky, P., & Valerio, M., & Skinner, J., & Al-Olimat, K. (2005, June), Calculation Of Electric Quantities In Three Phase Circuits Using Matlab Paper presented at 2005 Annual Conference, Portland, Oregon. 10.18260/1-2--14884