Print this page Calculating and Measuring Power in Three Phase Circuits
Joseph E. Fleckenstein, P.E.
Course Outline
At the outset of the course some basic electrical principles are reviewed. The course starts with single phase circuits and the equations applicable to these circuits. Next, the course moves into the topic of power in balanced three phase wye and balanced delta circuits. The derivations for commonly used equations and principles are reviewed. Unbalanced three phase circuits are also discussed, and the applicable power equations are presented. Finally, the course treats the various methods for measuring three phase power with instrumentation. The course includes a convenient summary of symbols and equations used for determining power and current lead/lag in three phase circuits.
This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.
Learning Objective
Upon completing the course, the student will:
- Be familiar with the equations descriptive of single phase currents and voltages;
- Be familiar with single phase power equations;
- Understand power factor and current lead and current lag in single phase circuits;
- Understand the principles of instantaneous voltage, peak voltage, instantaneous current, peak current and instantaneous power as applicable to single phase circuits;
- Understand the relationship between instantaneous voltage, instantaneous current, rms voltage and rms current
- Understand the equations applicable to instantaneous power as well as their derivations;
- Understand the concepts of instantaneous voltage, instantaneous current, instantaneous power as applicable to three phase circuits;
- Know how to apply power equations to calculate power in three phase wye circuits with balanced resistive loads;
- Know how to apply power equations to calculate power in three phase wye circuits with balanced capacitive or inductive loads;
- Know how to apply power equations to calculate power in three phase delta circuits with balanced resistive loads;
- Know how to apply power equations to calculate power in three phase delta circuits with balanced capacitive or inductive loads;
- Know how to apply power equations to calculate power in three phase wye circuits with unbalanced resistive loads;
- Know how to apply power equations to calculate power in three phase wye circuits with unbalanced capacitive or inductive loads;
- Know how to apply power equations to calculate power in three phase delta circuits with unbalanced resistive loads;
- Know how to apply power equations to calculate power in three phase delta circuits with unbalanced capacitive or inductive loads;
- Understand the methods for measuring power in three wire and four wire wye circuits; and
- Understand the methods for measuring power in delta circuits.
Intended Audience
This course is intended for electrical engineers.
Benefit for Attendee
The primary benefit of this course is that it provides a simple and easily understood means to calculate power in a variety of commonly found three phase circuits. This benefit can be especially helpful to those who need to correctly determine three phase power since most available texts on the subject treat the subject in terms that are relatively brief and often short of detail.
Course Introduction
The equations applicable to power in single phase circuits are relatively straightforward and, in comparison to three phase circuits, easily performed with dependable accuracy. Three phase circuits are different. In some instances the equations applicable to the various types of three phase circuits can be confusing and rife with potential errors. Yet, it is very often important that power be determined with correctness. This course is designed to present the subject of power in three phase circuits in a simple and easily understood manner. All commonly recognized configurations of three phase circuits are discussed and treated in detail.
Course Content
The course content is contained in the following PDF file:
Calculating and Measuring Power in Three Phase Circuits
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Course Summary
This course teaches the methods for calculating and measuring power in balanced and unbalanced three phase circuits. Any engineer who periodically finds a need to determine power in three phase circuits will find the course of value.
Related Links
The following links provide supplementary information on subjects related to the content of this course:
PDH Online Course E336, Calculating Currents in Balanced and Unbalanced three Phase Circuits
General information on three phase voltages: Wikipedia.com/wiki/three-phase_electric_powerQuiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
