Effect of gap nonuniformity on generated mechanical force and energy generated by powerful electromagnetic motor

Abstract

To increase the power generated by the electromag netic motor, for which the armature moves along the magnetic force lines, it is necessary to increase the area of the inductor poles. For a short stroke electromag netic motor (EM) that serves as the source of a pulse or vibration on the soil (a seismic source) [1], under the required force of dozens of tons and an operating gap limited by the load properties, the ratio between the area of the poles and the gap above them increases (the gap is less than 5 mm and the area of the poles is up to 1 m 2 ) so that it becomes difficult (in terms of structure) to achieve gap uniformity over the area of the pole. And the gap nonuniformity causes the mag netic flux redistribution between external poles and over the area of the poles and its concentration near the smaller gap (with high magnetic conductivity). Due to magnetic flux redistribution caused by the gap nonuniformity, several parts of the magnetic core is underloaded by the magnetic flux and it can happen that the electromagnet is not able to generate the force maximal possible under the uniform gap.The aim of the work is to estimate how the operat ing gap noniniformity influences the force and the mechanical work generated by the electromagnetic motor.To analytically estimate the inability of the electro magnet to generate the maximal possible force, let us examine how the nonuniformity of the gap (δ) between the armature and inductor caused by the armature shift relative to the inductor over width b 0 influences the performances of the electromagnetic motor ( Fig. 1). At the edges of the magnetic core, we set the deviation Δ from the gap δ mean at the middle of the magnetic core.To analytically estimate the worst case, let us limit the magnetic field induction in the area of minimal gap δ 1 . Let us assume that, during the motion of the armature and inductor, the value of Δ is invariable (the armature does not rotate relative to the inductor) if the gap δ mean decreases from δ o to Δ.In our analysis, we do not take into account the buckling and scattering fields, which is permissible for a short stroke electromagnetic motor, since these fields have an insignificant influence on the magneto motive and mechanical forces (less than 10% [2]). Let us assume that the drop in magnetomotive force at the magnetic core is insignificant and the magnetic field induction B in the minimal gap δ 1 due to the counter motion of the armature does not vary, which is achieved via corresponding variations in the magneto motive force as follows:Abstract-We have analyzed how the noniniformity of the operating gap influences the power and mechan ical work of the powerful electromagnetic motor. It is revealed that the gap nonuniformity can decrease the efficiency of magnetic core usage; however, in the excitation mode of electromagnetic motor operation with winding interlinkage close to a constant value, it does not significantly change the efficiency and response time of the electromagnetic motor. δ 2 δ mean δ 1 Δ a b 0 Fig. 1. Block di...