Calculation of some basic flux quantities in induction and other doubly-slotted electrical machines

The distribution of magnetic flux in the air gap of an electric machine is of fundamental importance in determining such quantities as stray losses, torque, reactances and magnetic noise. The author discusses some of the methods of approach which have been employed in the determination of the basic flux quantities in induction and other doubly slotted machines. By a new form of analytical approach, equations are obtained for some important quantities; these include accurate, but simple, equations for gap permeance and the amplitude of certain flux pulsations. Also developed are some basic equations for air-gap leakage flux, including its variation with rotor movement. Tests made on models in an electric-tank analogue confirm the equations obtained for this component of leakage flux and give some additional information regarding flux pulsations.