Dear Dennis... EN-Genius Network's Dennis Feucht answers your design queries in his new Circuit Design Clinic! December, 2006

EN-Genius Network presents a new, interactive analog design service to readers! Send us your design questions (with relevant data; schematics in JPEG or GIF, please) for some free engineering advice from EN-Genius Network's circuit consultant, Dennis Feucht, on how you might solve a design problem or improve circuit performance. Submissions may be edited for clarity or brevity, and submitters and their email addresses will remain anonymous (unless otherwise indicated). Please send your questions to Dennis here.

Power Electronics and Motor Drives: Advances and Trends
by Dennis L. Feucht

Bimal Bose is a prominent researcher in power electronics, mainly associated with high-power motor-drive systems. This book shows the maturity of a leader in the field in that he combines power conversion with motor control in one intertwined presentation. It is not an introductory book on the subject and is optimal for those who already have some grounding in the principles of power conversion, electric machines, and their control. It is oriented toward high-power techniques and applications, though much of it applies at any power.

The book is written in a novel format. When you are searching through a technical book for a topic you need to find out about, do you focus on the text or the illustrations? I suspect most of us look at the graphics. Yet books are written with graphics as support material for the text. Why not swap the priorities and let the illustrations drive the text instead? This storyboard format is used by Bose. Each illustration starts a page and is explained by the underlying text, which can flow onto the next page.

The book opens by explaining power semiconductor devices, then moves into phase converters and cycloconverters. Following this are voltage- and current-input converters and PWM techniques, after which a few chapters cover electric machines (mainly induction and synchronous motors), simulation, and digital control. The rest of the book applies advanced methods of control such as fuzzy logic and artificial neural networks to motor control. He gives some specific examples.

In its many pages the book presents much content, mostly in the form of system-level block diagrams. There are equations here and there, but very little derivation of them. The author assumes them from more basic books. There are also not many circuit diagrams having any detail -- mainly circuits in simplified form to express an idea.

Bose does a good job of conveying the basic ideas behind otherwise complicated concepts. In particular, he explains (mainly graphically) some of the newer forms of PWM control, including multilevel PWM and "space vector modulation," which he considers one of the larger breakthroughs and one of the latest in the field.

The advanced control methods applied to power electronics are particularly interesting. The use of artificial neural networks (ANNs) included examples of fuzzy logic and ANN application to motor drives. Other control methods such as adaptive control appear, making this a good book for control theorists to also delve into.

For those interested in alternative energy, wind generation makes an appearance, with some rather insightful explanation on wind turbines from a power electronics (instead of aerodynamic) viewpoint, including control schemes. Electric vehicles are discussed at some length, with an excellent coverage of the relative merits of hybrid vehicles.

Additionally, what the best kind of motor for electric vehicles is includes a personal note recounting Bose's days at GE Research in Schenectady, NY, from whence essentially all the motor experts of Bose's generation came, including my motor mentor, Allan B. Plunkett of AC Drives Technology, Sherwood, OR, Tom Lipo at the U of WI, Madison, a prolific contributor to advancement of the motor art, and Paul C Krause of Purdue U, who completed the theory of electric machines in the mid-1980s and wrote, Analysis of Electric Machinery, originally published by McGraw-Hill in 1986 (ISBN 0-07-035436-7), now available reprinted in paperback from the Armory Bookstore, Purdue U, 1511 Armory Bldg., Room B1, West Lafayette, IN 47907-1511 (ISBN 0-931682-38-X) for USD $33, payable to Purdue University. To me Krause's book is the most rigorous and elegant textbook on electric machines (with some deference to Enrico Levi of Brooklyn Tech and his and Marvin Panzer's Electromechanical Power Conversion, Second Edition, Dover # 0-486-60592-2, 1966) though Bose, Lipo, and another eloquent UWM motor professor, Donald Novotny (from the last I spoke with him), would disagree about the presentation of vector theory instead of the steady-state phasor theory to undergraduate students. Krause's book would make a good complement to Bose's because both tend to use the same generic GE motor notation and talk about motors and drives in a GE way.

Bose's book would be useful to anyone doing motor-drive design, especially for applications over 10 kW.