An engineer's diary

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  1. [No. 1] When is a fluxmeter not a fluxmeter?

    A fluxmeter is an integrating voltmeter. It never measures flux directly. It measures flux-linkage, the integral of voltage with respect to time. It is true that flux can be estim…

    • [No. 2] ABC of engineering calculations today

      Most engineering calculations take the path of analysis or simulation, shown in Fig. 1, A. Analysis has been established for a long time; but simulation is more recent, especially…

      • [No. 3] Görges diagram

        The polygonal diagram of H. Görges (Das Görgessche Durchflutungspolygon) dates from 1907. Although it is highly developed in German literature, until recently it has been rare in …

        • [No. 4] The Historic Claw-Pole Machine

          My grandson is interested in mathematics and history. Maybe it is an unusual combination, but both these subjects are helpful in looking forwards as well as backwards. In engineer…

          • [No. 5] Formulas and Equations

            What’s the difference between a formula and an equation? Take the examples,

            • [No. 6] The Periodic Table of Electric Machines

              When the archaeologists dig us up in 5,000 years’ time, they will find a large number of electric motors and generators. Who knows if they will understand what they find? They w…

              • [No. 7] Peripheral, marginal, second-order, inexact . . . and IMPORTANT!

                The finite-element method is very rarely exactly correct. Now surely that is an outrageous thing to say on the JMAG website! But what do we mean by exactly? The finite-element met…

                • [No. 8] Hysteresis

                  At the JMAG Users’ Conference in Strasbourg last October, Hiroyuki Sano (JSOL) and Yves Thiolière (Powersys) gave a detailed class tutorial on the hysteron, a defined trapezoidal …

                  • [No. 9] Can a magnetic circuit work without air ?

                    Recently the U.K. Magnetics Society sent a list of 10 questions for their magazine MagNews, in which the first question was “What is your favourite magnetic material?” In a hurry…

                    • [No. 10] RW

                      All electric machines use wire — usually of copper, but sometimes of aluminium. The electrical resistance R determines the I2Rloss (Joule loss) in each winding when the RMS curre…

                      • [No. 11] What is the finite-element method?

                        The idea in the finite-element method is to divide a difficult problem into a number of simpler problems which can be solved simultaneously; the solution to the difficult problem…

                        • [No. 12] The IPM

                          The IPM or interior permanent-magnet motor started its history as a line-start motor in the 1950s. At that time Alnico magnets were the best available, but their low coercivity me…

                          • [No. 13] Winding diagram for an AC motor

                            Here we see a winding diagram for a 3-phase AC induction motor or brushless PM motor (IPM), having 4 poles and 36 slots. This winding could in fact be used with any AC machine, i…

                            • [No. 14] Synthesis of AC motor windings

                              How should we synthesize a suitable winding layout for an AC brushless PM motor? While the properties of existing windings can easily be analysed using a spreadsheet program, it …

                              • [No. 15] Reading a winding diagram

                                Winding diagrams come in many different formats. There is no universal standard, but several common conventions can be found in the winding diagrams used by different manufacturin…

                                • [No. 16] Four rules of saliency

                                  We often hear the terms "salient-pole" or "non-salient-pole" in relation to electric machines."Saliency" is the idea of "projecting beyond the general outline", and it refers to t…

                                  PROFILE

                                  Prof. Miller was educated at the universities of Glasgow and Leeds, U.K., and served an industrial apprenticeship with Tube Investments Ltd. He worked for G.E.C. in the U.K. and General Electric in the United States. From 1986-2011 he was professor of electric power engineering at the university of Glasgow, where he founded the Scottish Power Electronics and Electric Drives Consortium. He has published more than 200 papers and 10 books and 10 patents, and he has given many training courses. He has consulted for several industrial companies in Europe, Japan and the United States. He is a Life Fellow of I.E.E.E. and in 2008 he was awarded the Nikola Tesla award.

                                  The Green Book: “Design of Brushless Permanent-Magnet Machines”

                                  The Blue Book: “Design Studies in Electric Machines” (June 30, 2022)