Electrical Engineering ⇒ Topic : AC Excitation of Magnetic Circuit

AC EXCITATION OF MAGNETIC CIRCUIT

Transformers and ac machines get excited from ac sources. An alternating current fed to the winding produces an alternating magnetic flux Φ. Let

                                                          ...............  (1)

                                                                  figure (a)

Effective value of the voltage induced in the N windings is:

The induced voltage e lags behind the flux and hence the exciting current by 90⁰. The polarity of the induced voltage will also be such as to oppose the flux change as per Lenz's law.