Electromagnetic　contactor　is　a　kind　of　widely　used　electric　product.　When　the　voltage　drops　suddenly,　the　contactor　will　be　open　or　closed　frequently,　and　the　circuit　will　be　influenced　seriously.　Based　on　the　research　of　CJ20-63A　contactor　dynamic　equations　were　established　during　closing,　closed　and　opening　processes;　the　movement　process　of　the　moving　contact　and　the　bounce　of　the　contacts　were　considered　at　the　meantime.　The　experimental　data　shows　the　model　is　correct.　Simulations　were　carried　out　with　respect　to　different　working　states　and　various　closing　phase　angles.　Influences　of　the　range,　duration　and　occurrence　time　of　voltage　drop,　and　the　variation　of　voltage　phases　on　performance　characteristics　of　contactors　were　analyzed;　the　result　indicates　that　the　influences　of　voltage　sag　on　the　contactor　are　related　to　the　closing　time　directly　in　the　closing　process;　and　a　critical　time　value　should　be　considered　after　the　contactor　is　closed.　This　research　provides　the　basic　for　the　further　study　on　the　intelligent　AC　contactor　with　anti-voltage　sag.　©　2011　Chinese　Society　for　Electrical　Engineering.