Magnetic　sensors　have　been　widely　used　for　current　measurements　in　diverse　industries.　In　order　to　achieve　a　large　current　measurement　without　an　iron　core　structure,　magnetic　sensors　are　often　arranged　to　be　a　circular　array　for　designing　a　new　electronic　current　transformer　(ECT).　However,　this　ECT　with　a　circular　array　of　magnetic　sensors　usually　suffers　from　tradeoffs　between　the　number　of　sensors　and　the　measurement　accuracy.　This　paper　visualizes　this　tradeoff　and　proposes　a　3-D　magnetic-field　model　to　analyze　the　impact　of　the　magnetic　sensor　circular　array　position　on　current　measurements.　We　develop　an　analytical　expression　of　the　current　measurement　errors　to　estimate　the　minimum　number　of　required　magnetic　sensors　and　point　out　the　acceptable　deviations　of　the　ECT　position　under　various　accuracy　classes.　Based　on　the　estimation　results,　we　design　a　new　circular　array　with　eight　magnetic　sensors　and　build　a　three-phase　current　measurement　system.　The　test　results　demonstrate　the　efficiency　and　the　robustness　of　the　designed　class-1.0　ECT,　which　successfully　maintains　accuracy　class　1.0　under　various　position　deviations　in　balanced　or　unbalanced　three-phase　power　delivery　systems.