The　V/f　control　method　is　one　of　speed　control　methods　for　induction　motors.　We　have　proposed　an　auto-boost　voltage　method　to　compensate　the　voltage　drop　of　stator　impedance　and　a　slip　frequency　compensation　method　to　decrease　the　speed　error　caused　by　the　change　of　load.　Stability　of　the　proposed　V/f　control　system　is　analyzed　by　root　locus.　Steady-state　torque-speed　characteristics　and　transient　responses　of　proposed　system　are　presented　by　experimental　system.　Compared　with　the　constant　V/f　control　method,　speed　accuracy　of　proposed　method　is　improved　in　various　speeds　and　loads.　©2008　IEEE.