Why is it called Park’s, not Blondel’s, Transformation?

The History of the DQ Transformation

Park’s transformation can be considered to be the single theoretical contribution that triggered the development of advanced design, control, and analysis of electrical machines (motors and generators). To most practicing engineers and researchers in this field, the story goes like this:

Robert H. Park (1902–1994)
André-Eugène Blondel (1863–1938)

After Nikola Tesla invented the AC machine in the 1880s, it took the electrical engineers over 3 decades of struggling with AC circuits analysis before Robert H. Park (1902–1994) published his seminal paper, in 1929, “Two Reaction Theory of Synchronous Machines”. In that paper, the brilliant young engineer solved the problem mathemagically by introducing the dq0-transformation that has been called after him, the Park’s transformation, which transforms the natural 3-phase AC reference frame into a fictitious 2-circuit rotating reference frame.

The Park’s transformation is a brilliant idea indeed, except that it was not invented by Park… Have you ever heard of André-Eugène Blondel (1863–1938)? Here is the complete story.

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Electric Motors Should be More Fun

We encounter mechanical phenomena all the time. We see things move, fall, spin, oscillate, break, etc. Electrical phenomena, on the other hand, are not always visible. Therefore, it has become a common practice to use mechanical analogies to explain and teach less visible concepts.

Classical analogy. Source

We compare electrons to water when explaining voltage, current, and Ohm’s law. The inductor is often compared to a spring, and the capacitor to a mass/inertia. The electrical resonance can then be compared to the mechanical resonance.

Even control engineers use mechanical analogies to illustrate their concepts; the proportional-derivative controller is nothing but a mass-damper system in that sense.

The theory of AC motors involves many difficult concepts, often explained with mathematical formulas and graphs. This is an obstacle to effective teaching and vulgarization. In this post, I propose 3 ideas to make the teaching of AC motors more fun. My goal is to stimulate more ideas and analogies; if you have some, please share them.

Continue reading “Electric Motors Should be More Fun”