Design, analysis and simulation of magnetic biased inductors with saturation-gap

Abstract

Permanent magnet biasing, is a known technique for increasing the energy storage capability of inductors operating in DC applications. The opposing flux introduced by a permanent magnet will extend the saturation flux limit of a given magnetic material. When full biasing of the core is achieved, the effective saturation current limit of a given inductor is doubled. This results in a smaller requirement in number of turns and area cross-section, allowing for smaller and/or more efficient inductors. By adding some switching elements, the benefits of biased inductors can also be used in AC applications. This paper presents a review of the scientific literature on biased hybrid inductors and the evolution of the used magnets and cores configurations. A recently developed biasing configuration, the saturation-gap, will also be analyzed and the design parameter will be identified using finite element software. The simulation results will be compared with empirical laboratory measurements on physical units.

Parametric transformer using PM‐inductors with saturation‐gap

“…11 shows the magnetic flux measured at the PMs, for the same interval of input current. Similar to the behaviour of the DC-bias PMI topology, the PMs lowers their operation point as the current increases, attempting to maintain a flux equilibrium at the SGs [20]. On the other hand, in the symmetric PM-PT topology, PM 2 and PM 3 present an almost constant operation point, and the variations in flux are maintained symmetrically by PM 1 and PM 4 .…”

“…In both cases, these PMI topologies present a fix nominal inductance, dominated by the reluctance of the air-gap, and would have limited value as PTs. A more recently develop PMI topology, referred as the saturation-gap [19][20][21], uses two non-gapped (UU shape) cores, biased by the same pair of PMs. The saturation-gap topology, is depicted in Fig.…”

“…where A C is the area cross-section of the magnetic core, and A W is the window area available for the windings. The energy storage capability, W of the inductor can be expressed as: (20) where I P is the peak current value, J max is the maximum current density allowed on the electric conductor, K u is the utilisation factor of the window area, A W and B sat is the saturation flux density of the core material. The expression (20) can only serve as an approximate estimation, since the accurate energy transfer in PTs is a more complex phenomena, involving the variation degree of primary and secondary inductances.…”

“…Using (20) and (21) the number of turns, N 2 and core dimensions, A C and A W can be selected. In order to simplify the analysis of primary-secondary energy transfer, initially it will be consider a…”

“…The dominant reluctance of the core is almost constant until saturation of the full core is reached, providing a linear nominal inductance until the saturation current limit, I sat . The nominal reluctance value of each of the SG segments, ℛ SG is approximately equal to the reluctance of one of the PMs, ℛ PM [19][20][21]…”