Generation Mechanism and Experimental Research of Unbalanced Radial Electromagnetic Force of Proportional Electromagnet

The function of proportional electromagnet is to proportionally convert the electrical signal into a mechanical quantity, the output axial electromagnetic force is proportional to the input current or voltage within the effective stroke of the armature. Because there is a radial gap between the armature and the guide sleeve, the armature is prone to be eccentric with the guide sleeve, and a unbalanced radial electromagnetic force is generated. The guide sleeve bears the radial pressure of the armature, and then generates friction that hinders the movement of the armature, which decreased sensitivity and linearity of the proportional electromagnet. The eccentricity problem of the armature and the guide sleeve is put forward in this article, the causes and hazards of unbalanced radial electromagnetic force are analyzed, the calculation formula of the unbalanced radial electromagnetic force is deduced, and simulation calculations and experimental research are conducted. The results reveal that the unbalanced radial electromagnetic force acting on the armature is approximately proportional to the eccentricity, and increases with the decrease of the axial working air gap between the armature and the basin-shaped pole piece, and rapidly raises with the increase of the coil current. To reduce the unbalanced radial electromagnetic force, a spline type armature is designed, which significantly reduces the eccentricity and unbalanced radial electromagnetic force, simultaneously reduces the contact area and motion resistance of the precise clearance between the armature and the guide sleeve, hence improves the sensitivity and linearity of the proportional electromagnet.