Magnetic field and currents in plane linear induction pumps with lateral busbars

S. V. Vasil'ev

Abstract
The distribution of the electromagnetic field in a plane, linear pump with lateral busbars is investigated. The problem is analyzed in a plane-parallel formulation. The induction of the primary field beyond the edge of the inductor is approximated by B_δ=B_δm k_Bexp(−\fracy−cδ), where B_δm is the amplitude at the level of the central line of the inductor, c is the half- width of the inductor batch, δ is the nonmagnetic gap, and the value of the coefficient k_B = 0.83. The variation in magnetic susceptance for the field of the secondary currents in the bus bar region is taken into account through the decrease in magnetic permeability in these regions according to the expression μ = μ₀k_μ1exp(−k_μ2\fracy−cδ), where μ₀=4π·10⁻⁷ h/m and k_μ1=k_μ2=1. The solution of the equations for the electromagnetic field is obtained in the form of a convergent power series. Analysis of the distribution of induced currents shows that when the channel is widened and the busbars are replaced with liquid metal, the useful component of the current density is increased. When the electrical conductivity of the busbars is sufficiently high in comparison to that of the liquid metal, a transverse edge effect develops in them. A portion of the currents flows out of the busbars and, locking in with the liquid metal, they strengthen the useful component there, and the direction of the longitudinal component is reversed. Under these conditions the pressure developed by the pump is larger than that developed in the case of a channel of infinite width. Theoretical results are compared with experimental graphs of the distribution of the inductance along the width of the inductor. Plates of stainless steel with copper busbars and a widening brass plate were used as loading. Satisfactory agreement was obtained.