The paper presents an analytical method which allows the estimation of the dynamic iron losses due to the slotting effect in a three phase induction machine. The case of a smooth air-gap machine supplied with nonsinusoidal waveforms is the subject of the initial developments. Their main interest is to show that elementary considerations, which are about the “copper” losses dissipated in stator and rotor cores, make it possible to find, in the case of rotating field, the usual formulations of the dynamic iron losses which appear in the literature. Then, this procedure is used to define the analytical expressions of the dynamic iron losses in case of sinusoidal supply taking the slotting effect into account. The calculus makes it possible to define these losses whether they originate from the fundamental or harmonic flux density waves distinguishing the effects according to stator or rotor core is considered. The variations of the different losses with the slip are given and it is shown that the slotting effect takes a non negligible part in the total dynamic iron losses. Moreover, it is shown that particular slotting flux density components, tied up with the slotting resonance phenomenon, have a main contribution.
The analysis of the iron loss distribution in the different parts of the machine makes it possible to define equivalent circuits of the induction machine iron cores. These circuits lead to estimate the steady harmonic torques generated by the iron rotor according to the iron rotor losses. Then, two particular experimental tests, which exploit the previous torques, allow the determination of all the parameters which intervene in all the components which define the total iron losses. Finally, the results of tests performed on an induction machine with rotor open windings and supplied stator, driven with a DC machine, are presented. The results validate the theoretical approach making clear that the slotting effect takes a non negligible part in the total iron loss definition.