Technical Data 4301 VP Effective August 2017 VERSA-PAC® Inductors and Transformers (Surface Mount) How to use multiple windings Discrete inductors combine like resistors, when connected in series or parallel. For example, inductors in series add and inductors in parallel reduce in a way similar to Ohm’s Law. L = L1 + L2 + L3...Ln Series L = 1/ [1/L1 + 1/ L2 + 1/ L3..1/Ln] Parallel Windings on the same magnetic core behave differently. Two windings in series result in four times the inductance of a single winding. This is because the inductance varies proportionately to the square of the turns. Paralleled VERSA-PAC windings result in no change to the net inductance because the total number of turns remains unchanged; only the effective wire size becomes larger. Two parallel windings result in approximately twice the current carrying capability of a single winding. The net inductance of a given PCM configuration is based on the number of windings in series squared multiplied by the inductance of a single winding (LBASE). The current rating of a PCM configuration is derived by multiplying the maximum current rating of one winding (IBASE) by the number of windings in parallel. Examples of simple two-winding devices are shown below: Series Connected (2 Windings) Parallel Connected (2 Windings) 10µH 1 Amp 10µH 10µH 1 Amp 1 Amp 10µH 1 Amp L = L x S2 I = I x P L = L x S2 I = I x P TOTAL BASE MAX BASE TOTAL BASE MAX BASE = 10 µH x 22 = 1 Amp x 1 = 10 µH x 12 = 1 Amp x 2 = 40 µH = 1 Amp = 10 µH = 2 Amps Where: LBASE = Inductance of a single winding P = Number of windings in parallel (use 1 with all windings in series) S = Number of windings in series IBASE = Maximum current rating of one winding 6 www.eaton.com/electronics