VR resolvers were developed as angle sensors for the motors of hybrid electric vehicles. Because the angle error of the resolver affects motor efficiency, the angle accuracy of the resolver must be improved. Results of investigations up to now showed the major cause of angle error of the resolver to be determined by imbalance of induced voltages on the coils caused by uneven distribution of magnetic flux around the coils. We, therefore, searched for a shape core that makes the distribution of magnetic flux more even around the coils. Finally we found that a thicker core stack, a smaller minimum air gap between the rotor and stator, and wider tooth tips of the core are effective for reducing the angle error.
