Field distribution and performance of copper-filled slotted solid iron rotors

The paper presents an extensive set of experimental results of the flux measurements on slotted solid iron rotors, in which the slots were filled with copper to establish the actual field distribution along the tooth and slot axes under sinusoidal-excitation conditions. These results, when compared with those for machines without copper, show first, that the tooth-axis flux distributions are identical in both cases, and secondly, that the leakage flux is much larger in machines with copper, and lead to the conclusion that this large leakage flux has little influence on the tooth-axis flux distribution and confines itself to a region very close to the tooth profile. An analysis for obtaining the field distribution along the tooth and slot axes has been developed, and performance equations for the machine have been obtained. The analysis gives the current-density distribution in the copper, and yields simplified expressions and equivalent circuits when the deep-bar effect in the copper conductor is negligible. Results of this analysis are in good agreement with the test results.