{"schemaVersion":1,"slug":"phase-sequence-indicator","name":"Phase-sequence indicator","kind":"symbol","abbreviation":"PSI","aliases":["phase rotation indicator","phase rotation meter"],"category":"measurement-protection","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Instrument that shows whether three-phase supply rotation is positive or reversed before motors are run or sources paralleled.","description":["A phase-sequence indicator connects to all three phases and shows whether rotation is L1-L2-L3 or reversed. It is used when commissioning motors, generators and supply changes, because wrong rotation reverses motors and prevents correct paralleling.","The instrument gives a check at one moment and does not protect anything on its own. If permanent protection against reversed rotation is needed, a phase-sequence monitoring relay with contacts must be shown instead of, or as well as, the indicator."],"readingNotes":["Confirm all three phases are connected in the stated order.","Check whether a protective relay is also required."],"drawingChecklist":["Show phase connections","State expected rotation","Reference commissioning check"],"distinction":"A phase-sequence indicator only displays rotation; a phase monitoring relay acts on incorrect rotation or loss of phase.","facts":[{"label":"Inputs","value":"Three phase voltages"},{"label":"Output","value":"Display only"},{"label":"Preview","value":"Independent educational concept; consult the applicable standard and project legend for the exact graphic"}],"references":[{"sourceId":"iec-diagrams","relevance":"IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced."}],"related":["phase-loss-monitoring-relay","47-phase-sequence-or-voltage-balance-protection","synchronoscope"],"artwork":"s28-phase-sequence-indicator","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Phase-sequence indicator mean?","introduction":"A phase-sequence indicator connects to all three phases and shows whether rotation is L1-L2-L3 or reversed. It is used when commissioning motors, generators and supply changes, because wrong rotation reverses motors and prevents correct paralleling.","example":"The instrument gives a check at one moment and does not protect anything on its own. If permanent protection against reversed rotation is needed, a phase-sequence monitoring relay with contacts must be shown instead of, or as well as, the indicator.","drawings":"Confirm all three phases are connected in the stated order. Check whether a protective relay is also required. A phase-sequence indicator only displays rotation; a phase monitoring relay acts on incorrect rotation or loss of phase.","terms":[{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Coil","meaning":"A wound conductor that can produce a magnetic field when energised."},{"name":"Phase","meaning":"One of the related AC waveforms in a power system."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"IEC graphical symbols for diagrams","url":"https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/"}],"detail":"Instrument that shows whether three-phase supply rotation is positive or reversed before motors are run or sources paralleled. A phase-sequence indicator only displays rotation; a phase monitoring relay acts on incorrect rotation or loss of phase.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/phase-sequence-indicator","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/phase-sequence-indicator.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"iec-diagrams","title":"IEC graphical symbols for diagrams","publisher":"IEC","url":"https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/","type":"standard","scope":"IEC 60617 and related symbol-design publications. Full database access requires a subscription.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced."}]}