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11. The calculus of the magnetic co-energy and attraction force

Lecture's plan

Introduction

  1. The importance of the magnetic circuit notion
  2. An example of magnetic circuit
  3. Defining the integration contour for the application of Ampère's theorem
  4. The application of Ampère's theorem - emphasizing the magnetic circuit
  5. Hopkinson's law
  6. Analogy between magnetic circuits/electrical circuits
  7. Application for modelling an electromechanical converter
  8. Defining the equivalent magnetic circuit
  9. The reduction of the equivalent magnetic circuit
  10. Flux-current relation
  11. The calculus of the magnetic co-energy and attraction force

The flux induced in the N whirls of the reel are expressed :

,

in which according to (7),

The magnetic co-energy 4 is then

The attraction force between the two elements of the ferromagnetic core is finally expressed:

It is in inverse ratio to e, having a maximum equal to:

for

4 which is, however, equal to magnetic energy, as presented in §2.4.3 of the book because, assuming a constant r, we face the case where the flux-current relations are linear.

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Last update: 2005, September, 30 | Translation: Sergiu Ivanov | Realization: Florin Ravigan, Cristian Vladu