An engineer's diary

[No. 65] Inductance

Inductance may come as a shock to anyone who thinks that V = I × R. That delightfully simple expression of Ohm’s law is not the whole story. For sure, if we have a coil connected …

[No. 66] Axial flux

Axial-flux machines are currently in vogue. With an internet search we can quickly find numerous examples, including many videos of home-made machines and some notable products an…

[No. 67] Harmonic waves in AC machines

The famous Park’s equations for the d- & q-axis voltages in synchronous machines were developed from the concept of sine-distributed armature ampere-conductors. The fundamental or…

[No. 68] Torque waves (and the insane simplicity of the torque equation)

Smooth torque. Isn’t that what we get from electric machines?　They certainly appear to produce smooth torque. Unlike internal combustion engines, they have no flywheels or balanc…

[No. 69] Animation

The educational and commercial importance of animation can hardly be overstated. We see it almost everywhere, and it now has a significant role in even the most traditional areas …

[No. 70] Don’t make your eddy-currents angry !

Imagine a block of permanent magnet material in an IPM, Fig. 1. Our line of sight is parallel to the direction of magnetization, at right angles to the plane of the diagram.

[No. 71] p.u.

The first time I saw the expression “p.u.” was in an examination paper on electric power-systems, when I was a student-apprentice. Fortunately it was the previous year’s paper, no…

[No. 72] Properties of the dq-axis transform

In any system of calculations using dq-axis theory for synchronous machines, the question will arise, as to which transform should be used. The two transforms shown in Fig. 1 are …

[No. 73] Butt joints and other gaps in electric machines

There are several gaps and joints (or interfaces) in any electric machine, and we can classify them as follows. A. Intended gaps. The air-gap between the stator and the rotor is t…

[No. 74] Uncertainties in design calculations for electric machines

Although these are the words of a forlorn princess wringing her hands in a castle, concerned about uncertainties in her design space, they could surely have been expressed by any …

[No. 75] What finite-element analysis can and cannot do

Is FE Man telling the truth? Let’s pretend somebody has sued him for making false claims. We’re in the High Court, and the lawyers pose two carefully-worded questions: 1 Can the f…

[No. 76] Maxwell’s Apprentice and the Flux Gusher

Video 54 introduced a short series of three or four videos with an attempt to compare flux-linkage captured at the terminals of an electric machine with oil captured at the well-h…

[No. 77] Mathematics in Action

In a recent session of the Biggar Science Café entitled Mathematics in Action, I found it very easy to borrow some examples of applied mathematics from the world of modern automot…

[No. 78] Atomic Simulation

Atomic simulation — Imagine the simulation of a system or an electric machine atom by atom, indivisible particle by indivisible particle, in which there is one discrete finite ele…

[No. 79] The Alexanderson Alternator — An Axial-flux Marvel

Alexanderson alternators had these design parameters: Electric machine designers will surely look on these figures with admiration—even with astonishment—given that the era of the…

[No. 80] The Shadow-Winding

The shadow-winding is useful for measuring generated EMF and inductance in prototype electric machines. Typically it consists of a complete phase winding wound in the same slots a…