| Abstract |
Although brushless resolvers have been widely used as angular position transducers, they are expensive due to their intricate construction, having a rotary transformer which supplies current to the exciting coils wound on the rotor poles. The authors have shown theoretically in the present paper that a resolver without rotary transformer or brushes can be realized, by a simple construction which consists of a stator core with both 4-pole exciting windings and 2-pole output ones and the rotor core carrying no windings. In this resolver the rotor core has a minimum gap at one side and a maximum gap at the opposite side of the rotor cross-section, and is characterized by an outer surface form which makes the gap permeance vary in proportion to cos omega, where omega represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. A method for determining the rotor form that embodies this gap permeance variation is also shown. It was confirmed by simulation and experiment that the 2-phase output voltages of a model designed according to this theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through a conventional resolver/digital converter was within acceptable engineering accuracy. |
