Technical Tools & References


Utilization of bobbin ( spool or drum) cores is a simple and cost effective way of designing a power inductor. This calculator makes use of standard bobbins in Fair-Rite's # 77 material - so frequency is limited to about 10 MHz, depending on the winding. Maximum possible NI is 750 Ampere-Turns, maximum current is 15 Amps ( using AWG# 10) and minimum wire gauge is AWG# 30. The user enters target inductance and maximum operating current : the first thing the calculator does is selects a minimum wire gauge based on 700 cir-mils/Amp ( 2.8 Current Density. Then the calculator estimates number of turns required and selects the smallest size bobbin core capable. Uncoated bobbins, magnet wire and 90% copper fill ratio are assumed.

Enter Target inductance (Ls in uH)
Enter maximum operating current (Imax in A)
Recommended Fair-Rite core
Smallest wire to use (in AWG)
Number of turns (N)
Minimum achievable inductance (Lsmin in uH)