Linear and nonlinear reactors with nickel-iron alloys in power circuits

Abstract

The optimum design of linear inductors used in switching regulator circuits is outlined with regard to core and winding losses. It appears that tape wound toroidal cores with 36-48 percent Ni-Fe alloys (0.03-0.05 mm thick) with one air gap are well suited for these applications because of their small iron losses and their particularly wide range of dc biasing. Non-linear reactors are required in thyristor circuits as protective elements. Newly developed alloys (specially annealed 65 Ni-2.5 Mo-Fe and 79 Ni-4 Mo-Fe) exhibit particular advantages for these applications with respect to the excursion range of induction and the pulse permeability. For RFI suppression in SCR circuits, nonlinear chokes prove to be more effective than the hitherto existing solutions. Optimal results are realized with tape wound cores composed of several magnetic materials (e.g., 36 NiFe and 2.5 SiFe or 72-81 Ni-1-3 Mo-Fe and Fe). In particular, the acoustic noise levels produced by these chokes are considered.