Geometrical factors affecting magnetic properties of wound toroidal cores

Although toroidal cores wound from grain-oriented silicon iron strip are basically simple devices used in many applications, their magnetic properties are known to vary in a complex manner with core dimensions. The theoretical effects of radial magnetic field and flux density variation, interlamina normal flux, and winding stress on the real and apparent power loss and the permeability of a range of toroids with typical commercial dimensions are discussed. Comparisons are made with actual performance. It is shown that the radial variation of flux densities has a very small effect on the power loss and permeability but the interlamina normal flux has an influential effect, particularly in small-diameter toroids. It is shown that to obtain low losses and magnetizing currents, toroids should be designed using wide strips having large internal diameter and low buildup