An engineer’s diary

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  1. [No. 51] Current-density J

    Next in alphabetic sequence is J — which could stand for 'JMAG' or 'JAPAN', but instead let us think of J as the common symbol for current-density. Sometimes when I think about c…

    • [No. 50] Insulation

      In this series of Engineer’s Diary, the topics are selected by following the letters of the alphabet, giving an almost random walk through the field of electrical engineering. ‘I’…

      • [No. 43] Exponential function and complex numbers in electrical engineering

        Euler [1707-1783] is closely associated with this equation which has been described as the most beautiful equation in mathematics. It is sometimes regarded as having mystical sign…

        • [No. 52] JMAG goes to work

          This new book is written for engineers concerned with the design and development of electric machines.

          • [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. 39] The magnetic vector potential

              A is commonly used as the symbol for magnetic vector potential, just as B is used for flux-density or "induction", and H for mag…

              • [No. 48] Helical winding

                The helical winding (Figs. 1 and 2) was originally examined as a candidate air-gap winding for large 2-pole superconducting alternators at International Research and Development C…

                • [No. 49] Hair-pin winding

                  The hair-pin winding has become prominent in drive-train motors for electric and hybrid vehicles, with many creative examples in manufacturing. Although ‘push-through’ hair-pin co…

                  • [No. 46] Harmonic poles

                    The number of poles is perhaps the most basic parameter in the design of an electric machine. When we speak of this parameter, we usually mean the number of working poles. Fig. 1 …

                    • [No. 35] The position of wires in the slot

                      In the armature of a permanent-magnet DC motor, the wires usually occupy a rather untidy pattern in the slot — not because there is anything wrong, but simply as a result of the w…

                      • [No. 41] Coils and Conductors

                        The two previous Engineer’s Diaries were titled A and B: A for vector potential and B for flux-density. This is C, for coils and conductors — and maybe for “crocodile clips” (croc…

                        • [No. 54] K : Kron

                          Last month the letter K failed to provide a ready supply of suitable electrical engineering topics for the Diary, so we borrowed the German term Kennlinie.

                          • [No. 42] Diameter

                            D is for diameter! — surely the most fundamental of all engineering dimensions, at least in electric machine design. It is so important, we might ask ourselves why computer monito…

                            • [No. 53] K : Kennlinie, ken-lines, and cissoids

                              Progressing through the alphabet of electrical engineering topics, we come to the letter K, and for this Diary I have to say I had some difficulty finding a suitable topic beginni…

                              • [No. 34] Some essential features of the synchronous reluctance motor

                                In Column 31 we deduced several inherent features of the switched reluctance motor merely by inspecting its cross-section and considering the main flux-paths, and here we will do …

                                • [No. 31] Some essential features of the switched reluctance motor

                                  Every type of electric motor has certain essential features. One way to begin to understand them is to make a drawing, and at the same time make a list of observed features and ch…

                                  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)