Iron loss measurement technique and experience for flux including DC offsets

The authors are engaged in a programme of work to develop an improved model of iron loss for the use in the design of switched reluctance machines. This has necessitated (i) the development of equipment to measure iron loss in samples of steel over a wide range of frequencies for a variety of impressed flux waveforms, including a DC bias, and (ii) measurements of the loss in a static basic 2-pole switched reluctance machine. The paper gives details of these systems and results demonstrating the agreement with the new model. Two interesting effects which have emerged are also explained - the first shows the unexpected effect of the nonlinear magnetisation curve on the relationship between mean flux and mmf and the second concerns the decay of flux and eddy currents under conditions of discontinuous excitation