ECE431

ECE431 (Electric Machinery) is a 4-credit-hour senior/graduate level course that satisfies the Technical Electives requirement for ECE majors and counts as a hardware lab course. It is offered only in the spring.

Content Covered

Power measurement, three-phase power (ECE330 review)
Power factor control
Single-phase transformer tests and theory
Saturation and harmonic effects in three-phase transformers
Per unit analysis
Reluctance machines and stepper motors
Induction motor testing, theory, and performance
DC machine testing, theory, and performance
Synchronous machine testing, theory, and performance
Digital simulation of machine dynamics
Basic DC control systems and electric machines as inverters
Electric machine research

The first part of ECE431 is a review of ECE330 with some new content intertwined. The course startes by going over three phase power, the two-wattmeter method, wye and delta connected loads, power factor correction, and ideal transformers. The class then starts to discuss the problems with ideal models and how to truly represent a transformer or machine using an equivalent circuit. At the same time, in the lab you get to create the equivalent circuit model of a transformer or machine from scratch using a variety of different tests that you learned in class. The next part of the class is all about studying various types of electric machines. Every week in the lab, there is a different electric machine to be studied, whether that be an induction motor, synchronous generator, DC motor, or even a stepper motor. The content in the class is directly applied to the lab which does a fantastic job at solidifying understanding. As the class starts to wrap up, there is usually a small research project that you can work on with your lab partner or whoever you want. You must write a short research paper about something relevant to the field of electric machinery and give a 5 minute presentation with your partner.

In the lab, students apply a variety of methods and tests learned in lecture to study electric machines. The goal of most labs is to be able to represent the behavior of the motor with an equivalent circuit and to compare it to the behavior of the theoretical model. For example, one of the labs focuses on understanding the motor regime of an induction machine. You begin by performing basic tests to find the equivalent circuit parameters and then graph the theoretical Torque-Speed curve based on the measured values. You then actually measure the points on the Torque-Speed curve and construct it based on the data. The final step is to compare the accuracy of the equivalent model to the measured Torque-Speed curve.

The final lab is a culmination of everything that you learned in the class. The whole power lab is turned into a microgrid that students have to start up and synchronize to eventually toast some bagels! This lab highlights the complexity of the grid and how hard it is to manually ensure stability under a variety of different load conditions.

Prerequisites

ECE330

ECE330 is the only official prerequisite to the course. It is essential that students take this course before ECE431 as this class builds on the content. It is recommended that students have already taken a few lab courses as this is a senior/graduate level course and the labs require familiarity with oscilloscopes, Variacs, and designing your own wiring diagrams. There is also a programming assignment where you simulate a synchronous motor's dynamic response to sudden loads using any language you want and a lab that requires students to use an arduino to control a stepper motor, so it is recommended that students have some coding experience under their belt.

When to Take it

This course is one of the logical next steps in the power systems sequence after ECE330. Many students feel like this class solidifies and continues on from ECE330 material while also reinforcing complex ECE330 content through the labs. Take this course if you are at all interested in electric vehicles, power systems, and/or the electric grid. Definitely take this class if you want to go more into depth on the theory and machines first introduced to you in ECE330.

Course Structure

This course has semi-weekly homeworks, two midterms, weekly prelabs and labs, a written lab report due every week, a final research project, and one final.

The homeworks start weekly and tend to lighten up as the semester goes on. On exam weeks, the homework due date is usually extended. Homework sets are generally not too difficult and will primarily contain calculations, but there are some problems that test deeper understanding of the course content. Many of the homework problems are gone over in class before the assignment is due. Some homeworks will take under an hour, while others require more calculation and can be generally annoying. Students who pay attention and stay engaged in lecture will find these homeworks to be conceptually simple.

The midterms are in class (1 hour) and usually not very difficult with the averages being in the high 80's to low/mid 90's with small standard deviations. Very few practice exams are given out (1-3 per exam) and students. Cheatsheet policies may vary depending on the semester and the lead instructor. For the Spring 2023 semester, students were allowed to bring one double-sided 8.5x11 cheatsheet to the first exam, two double-sided 8.5x11 cheat sheets to the second exam, but only two double-sided 8.5x11 cheat sheets to the final exam. Students were highly recommended to reuse cheat sheets from prior exams, although this was not enforced.

Overall, the course requires about 8-12 hours a week based on how difficult the lab is for the given week and also how much effort you put into the report.

Instructor

Professor Haran usually teaches this course. Haran has an extensive background within electric machines as he is the head of the power group and oversees many research projects related to electric machinery. He has experience working as an engineer at General Electric.

Course Tips

The lab reports can be complicated based on the week and may need extra time to complete, so start early! Especially start the induction machine lab report early as it is one of the longest reports that you will have to write in the course. Professor Haran usually finishes the content early in the class period and expects students to ask questions, so do not be afraid to ask a question no matter how simple you may think it is.

The course can get overwhelming quickly as you keep learning about different types of electric machines at an increasing pace. Be sure that you understand the content because the exams (and homeworks) often ask you to explain what would happen if a parameter changed and why that would occur.

Make sure you fully understand the prelabs before the labs so you do not have to redo your lab experiment and stay after (a common occurrence in this class). Also do not be afraid to ask a TA to double check your wiring before you connect power, you will be working with high voltages and high currents which can potentially harm you if you do not wire the circuit correctly.

Life After

This is currently the only ECE class on electric machinery, except for ECE432 (Advanced Electric Machinery) which has not been taught in over a decade. Related classes include ECE333 - Green Electric Energy(more on the grid and green energy), ECE464 - Power Electronics (if you like EVs, inverters, power in general), ECE476 - Power System Analysis (focus on the grid with many overlapping concepts), and ECE486 - Control Systems (more on control of electric machines).

If you want to continue down the power path, it is recommended to take ECE486, ECE464 (and the lab section, ECE469), and then ECE515 as they are prerequisites for many graduate level power courses.

Infamous Topics

DC Machines: despite the seemingly simple nature of these machines, they are complicated in almost all aspects. The sheer number of different types of DC machines and the effect of current vs voltage control on the operating point behavior often confuses students. Some DC machine problems also require students to remember rotational mechanical physics from PHYS211 which is a struggle for many.
Synchronous machine transient response: Setting up the Delta-Power curve for a synchronous machine based on a given word problem, figuring out which areas to shade in, setting up the equal area criteria integrals, and solving the set of equations is a complex task that requires practice.
Velocity: This class does many conversions between electric radians and mechanical radians which is a new concept to some. Because of this, there are a lot of variables that can easily be confused which is frustrating for many students. Many equations include the lower case omega with up to 4 different subscripts.
Reluctance machines: analysis of phase inductance as a function of angle is complicated as it has to do with the setup of the rotor and stator. There is not necessarily one formula which will help you produce the graphs so students have to figure out a way that works best for them which usually involves a fair share of geometry.