Glossary of Motor Terms
Faraday’s law, Electromagnetic induction, Electromotive force
The meaning of Faraday's electromagnetic induction experiment is often explained by a model as shown in Fig. (a). The phenomenon of electromagnetic induction is described by the following dynamic equation including the time derivative with respect to Ampere's static integral law.
![](/-/media/www-nidec-com/technology/motor/glossary/item/faraday_law-01.jpg)
Here, "e" on the left side is a voltage generated by temporally changing the flux linkage ψ, and is referred to as the electromotive force. The flux linkage ψ is the physical quantity obtained by multiplying the magnetic flux φ by the number of turns, N. As explained in (b), φis the two-dimensional (surface) integral of B・n across the magnetic flux as given by
![](/-/media/www-nidec-com/technology/motor/glossary/item/faraday_law-02.jpg)
If we combine the above two relationships and express it in differentiation form with respect to spatial locality, we get the following:
![](/-/media/www-nidec-com/technology/motor/glossary/item/faraday_law-03.jpg)
And this is how it is described in many textbooks.
![](/-/media/www-nidec-com/technology/motor/glossary/item/faraday_law-04.jpg)
![](/-/media/www-nidec-com/technology/motor/glossary/item/faraday_law-05.jpg)
(a) What is electromagnetic induction? Even if there is no electrical connection between the primary winding and the secondary winding, if there is a magnetic interlocking relationship, a voltage is generated between the secondary winding terminals due to the current on the primary side, and it flows.
![](/-/media/www-nidec-com/technology/motor/glossary/item/faraday_law-06.jpg)