{"schemaVersion":1,"slug":"4-master-contactor","name":"Master contactor","kind":"function","abbreviation":"4","aliases":["main master contactor","ANSI 4","IEEE device 4"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEEE / ANSI"],"summary":"Switches the main control or operating circuit under the unit's master command.","description":["Switches the main control or operating circuit under the unit's master command.","In a drafting package, connect this reference to the master control coil and power contacts. The associated drawing should trace the circuit energised by the contactor; the number identifies the role and does not specify the terminal arrangement, ratings or operating settings."],"readingNotes":["Identify the master control coil and power contacts.","Trace the circuit energised by the contactor."],"drawingChecklist":["Label the master control coil and power contacts.","Cross-reference the circuit energised by the contactor.","Identify the device tag, manual revision and logic drawing that define this implementation."],"distinction":"A master contactor is a switching device; the master element numbered 1 can be a control function.","facts":[{"label":"ANSI / IEEE function number","value":"4"},{"label":"Drawing context","value":"The master control coil and power contacts"},{"label":"Application scope","value":"Protection or apparatus-control role; exact implementation is defined by the equipment documentation."}],"references":[{"sourceId":"pub-function-sel-numbers","relevance":"Public manufacturer number/name association. Drafting explanations are independently written."},{"sourceId":"ieee-functions","relevance":"Normative device-number publication; exact edition wording and compliance require the licensed standard."}],"related":["contactor","52-ac-circuit-breaker"],"artwork":"pub-function-box","publishedOn":"2026-10-13","updatedOn":"2026-10-13","provenance":"independent-public-research","url":"https://eloragrid.ai/protection-functions/4-master-contactor","illustration":{"url":"https://eloragrid.ai/library/illustrations/4-master-contactor.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pub-function-sel-numbers","title":"ANSI device-number and suffix reference table","publisher":"Schweitzer Engineering Laboratories","url":"https://selinc.com/pt/products/tables/ansi/","type":"manufacturer","scope":"Public Portuguese-language base-number and application-suffix table. Used to cross-check public number associations. Application-specific and historical labels need the selected drawing legend; this table is not a substitute for the licensed IEEE standard.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public manufacturer number/name association. Drafting explanations are independently written."},{"id":"ieee-functions","title":"IEEE C37.2-2022: power-system device function numbers","publisher":"IEEE","url":"https://ieeexplore.ieee.org/document/9984140","type":"standard","scope":"Device function numbers, acronyms and contact designations. The full publication may require access through IEEE.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Normative device-number publication; exact edition wording and compliance require the licensed standard."}]}