Numerical predictions versus experimental findings on the power-harvesting output of a NiMnGa alloy

The effect of magnetic field orientation on the open-circuit voltage of Ni–Mn–Ga based power harvesters

“…Following Nelson et al (2014), we further investigated experimentally power output with bias field at an angle for two orientations of the MSMA, with the external field along and against the twin boundary (configurations iii & iv, and i & ii, respectively) as shown in figure 3(a). The resultant of the axial and transverse field components acts at a 'tilt angle', θ indicated in figure 3(a).…”

“…However, unlike Nelson et al (2014), in this work we use separate axial and transverse magnets to get a much wider range of orientations for the external field and more uniformity in the applied field. Furthermore, in this work, we use finite element analysis (FEA) to quantify the field within the MSMA, and for one set of experimental tests, we use FEA to design the experimental magnetic loading in order to get the desired magnitude and direction of the magnetic field inside the MSMA.…”

“…Schiepp et al 2012, Schluter et al 2012, Wegener et al 2014, however, such a low stress can be advantageous for power harvesting or sensing as it is easier to provide. Suorsa et al (2004), Karaman et al (2007), Bruno et al (2012), Kohl et al (2013) and Nelson et al (2014) demonstrated that high-frequency cyclic compressive, or impact loading, can induce power output with MSMAs. The power output is due to a deformation-induced change in magnetization, a.k.a.…”

On the power and efficiency of Ni2MnGa magnetic shape memory alloy power harvesters

“…The side coil setup [1,8,9] and the surrounding coil setup [7,10,11], as shown in figures 2(a) and (b), respectively, are commonly used for developing MSMA-based power harvesters. In the former configuration the pick-up coil is wrapped around a magnetic core that is part of the magnetic circuit which generates the bias field, while the latter configuration involves placing a pick-up coil directly around the MSMA element.…”

“…Using the surrounding coil setup, Karaman et al [10] reported a maximum peak voltage of 280 mV at an operating frequency of 10 Hz. Nelson et al [11] and Guiel et al [7] also used the surrounding coil setup and reported an increase in the open circuit voltage by approximately 15% and 900%, respectively, when exposing the MSMA to both an axial and a transverse bias field (see figure 2(c)). The axial component of the bias magnetic field causes a larger change in magnetization along the axis of the pickup coil because the magnetization vectors in V1 are aligned with the axial field.…”