A sine-cosine resolver, which has high measurement accuracy and reliability, is widely used as an angular position and speed sensor in many fields of industry. Attempts to further raise the robustness of a resolver have been made, and as a result, a pancake brushless resolver has been developed.
A pancake resolver has no traditional collector that brings energy into the rotor but feeds current into the rotor through a rotary transformer located at the stator edge. The advantage of such structure over the traditional resolver with a collector is absence of relative movement between mechanical parts that causes wear, vibration and noise. But the disadvantage is that a rotary transformer consumes most of the power that a pancake resolver needs.
Ro Yong Sim, a researcher at the Faculty of Electrical Engineering, has proposed a new structure of a rotary transformer for reducing consumed power of a pancake resolver. The core material she used was electrical steel containing silicon. This material has large resistivity, which can result in lowering core loss.
She has also proposed a scheme for cutting some air gaps in the core to block the path of eddy current and to further decrease core loss. She estimated the proper amount of silicon and the size of air gaps through field analysis by Ansoft Maxwell and experimental results.
The simulations by Ansoft Maxwell software and the experimental results in a resolver manufacturing plant have shown that a newly designed rotary transformer consumes less power (71.7%) than before.
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