INFLUENCE OF FRINGING ON SERVOVALVE TORQUE-MOTOR CHARACTERISTIC

Abstract

Servovalve torque-motors are controlled changing magnetic flux through air gaps at the armature ends. The traditional theory gives the torque on the armature assuming uniform distribution of the flux over the air gaps. However, experimental facts contradict with the assumption because the flux density becomes uneven by the fringing at the gaps. To express the torque with acceptable accuracy, two coefficients are necessary. The first is the ratio of the mean flux density and the flux density at the center of the gap. The second is the ratio of mean of squared flux density and the square of the flux density at the center of the gap. This paper explains the necessity of these coefficients and presents the procedure to find them. The obtained result forms a part of design criteria for servovalve torque-motors.