An engineer's diary

[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. 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…

[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. 36] Some essential features of the induction motor – 1

In Column 34 we deduced several inherent features of the synchronous reluctance motor merely by inspecting its cross-section and considering the main flux-paths, and here we will …

[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. 21] What is a space-vector?

A space-vector — let us say, a space-vector of current — is a single complex number representing the combined effect of all three phase currents in an AC machine at a particular i…

[No. 17] Classification of electric machines

The diagram shows most of the electric machines in common use, together with the two reluctance machines which are rare but interesting. Classification is much more than an acade…

[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. 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. 19] The number of poles in a rotary electrical machine

The figure shows the some of the effects of pole-number on the magnetic field in a rotary electrical machine.It is a highly idealised figure: the winding is a current-sheet in the…

[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. 40] Flux density

The six images are listed below in the wrong order. Please, before you read this, try to decide what the Bees are showing. The answer is given at the end.

[No. 24] Synchronous torques in induction motors

Fig. 1 shows two types of irregularity in the speed/torque characteristic of an induction motor — the asynchronous torque dip and the synchronous torque dip. These are sometimes c…

[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…

[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…