The　rotor　flux　error　affection　on　the　stability　of　the　induction　motor　full-order　speed　adaptive　rotor　flux　observer　was　studied　using　the　voltage　model.　The　positive-real　property　of　the　forward　path　transfer　function　of　the　observer　equivalent　error　system　was　analyzed.　Stability　domain　border　equations　in　ω1-ωs　plane　were　derived.　A　modified　rotor　flux　error　model　excluding　a　pure　integrator　was　suggested.　Affection　of　the　modified　model　on　open-loop　zeros　plots　of　the　linearized　equivalent　speed　control　system　was　investigated,　and　the　stability　region　distribution　in　all　motor　operation　modes　was　studied.　Research　results　indicate　the　stability　region　is　enlarged　by　amplifying　the　rotor　flux　error.　The　observer　with　the　modified　model　is　stable　in　the　low-speed　region　with　regenerative　loads　but　unstable　in　low-speed　motoring　mode.　Simulation　results　illustrate　the　adaptive　observer　with　combined　speed　adaptive　laws　is　stable　in　all　motor　operation　modes.