Theory and Characteristics on Novel Variable Reluctance 1X Resolver.

Abstract

Although brushless resolvers have been widely used as angular position transdusers, they are expensive due to the intricate construction having rotary transformer which supplies the exciting coils wound on the rotor poles with the current.The authors have shown theoretically in the present paper that the resolver without rotary transformer or brushes can be realized by the simple construction which consists of the stater core with both 4-poles exciting windings and 2-poles output ones and the rotor core carrying no windings. In this resolver the rotor core has the minimum gap at one side and the maximum gap at another side of a diameter and is characterized by the outer surface form which makes the fluctuation part of gap permeance vary in proportion to cos θ, where θ represents angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the above mentioned gap permeance variation is also shown.It has been comfirmed by not only simulation but also experiment that the 2 phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy.