Motor Band Losses

It is shown that railway motor band losses are of appreciable magnitude, sometimes sufficiently large to be detrimental to the cooling of the machine. By tests of a small machine checked against those of a large one, the band losses are found to vary according to the 1.7 power of the frequency and from the 1.35 to the 1.8 power of the induction, depending on the width and type of band. These losses are shown to be due chiefly to the change in the radial component of the flux as the band passes by the pole tip. For average bands, about 15 per cent of the losses (hysteresis and eddy) are due to the tangential flux in the bands. A typical set of curves is shown for calculating band losses.