{"schemaVersion":1,"slug":"control-transformer-fused-primary-interface","name":"Control-transformer fused-primary interface","kind":"symbol","abbreviation":"CFI","aliases":["Switchgear control-power supervision","switchgear Switchgear control-power supervision","switchgear","Switchgear","Auxiliary AC source","Control transformer primary"],"category":"control-circuits","drawingTypes":["Schematic"],"referenceFamilies":["Manufacturer"],"summary":"Shows the protected primary connection of the selected control-power transformer.","description":["Shows the protected primary connection of the selected control-power transformer. Control power supplies the command, protection and indication equipment associated with a switchgear assembly. The drawing must distinguish the source, each distribution branch and the functions lost if that branch fails.","In a switchgear lineup, separate protected branches may feed trip coils, closing coils and protection electronics. Their alarm contacts help the station controller identify which operating capability is unavailable. For this reference, the drawing identifies “Auxiliary AC source” at the input and “Control transformer primary” at the output. Fuse selection follows transformer and protection data.","Follow the actual positive, negative or neutral returns and the protective device on each branch. A healthy voltage indication does not establish that every downstream path can deliver its required operating current. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation."],"readingNotes":["Start at the named input: Auxiliary AC source. Identify its source device or document and the state represented on the drawing.","Follow the named output: Control transformer primary. Cross-reference its destination and separate the command from confirmation that the equipment responded.","Fuse selection follows transformer and protection data.","Follow the actual positive, negative or neutral returns and the protective device on each branch. A healthy voltage indication does not establish that every downstream path can deliver its required operating current."],"drawingChecklist":["Label the source and connection reference for auxiliary ac source.","Identify the destination and defined state of control transformer primary.","Record the equipment or control-document revision supporting this functional block.","Check this application limit in the project design: Fuse selection follows transformer and protection data."],"distinction":"Fuse selection follows transformer and protection data. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.","facts":[{"label":"Representation","value":"Functional block"},{"label":"Installation focus","value":"Switchgear"},{"label":"Input / boundary","value":"Auxiliary AC source"},{"label":"Output / connection","value":"Control transformer primary"},{"label":"Lookup label","value":"CFI is a library lookup label, not a standard device designation."}],"references":[{"sourceId":"pi26-station-power","relevance":"Public technical context for switchgear control-power supervision. Independent AC and DC sources for station auxiliary power. The application text and educational graphic are independently authored; the publisher does not certify this representation."}],"related":["relay-coil","ac-to-dc-power-supply","control-transformer-secondary-distribution-interface"],"artwork":"pi26-control-transformer-fused-primary-interface","publishedOn":"2026-11-03","updatedOn":"2026-11-03","provenance":"independent-public-research","representation":{"type":"functional-block","focus":"switchgear","family":"control-power","input":"Auxiliary AC source","output":"Control transformer primary"},"plainEnglish":{"title":"What this block does","introduction":"Shows the protected primary connection of the selected control-power transformer.","example":"In a switchgear lineup, separate protected branches may feed trip coils, closing coils and protection electronics. Their alarm contacts help the station controller identify which operating capability is unavailable. For this reference, the drawing identifies “Auxiliary AC source” at the input and “Control transformer primary” at the output. Fuse selection follows transformer and protection data.","drawings":"Start at the named input: Auxiliary AC source. Identify its source device or document and the state represented on the drawing. Follow the named output: Control transformer primary. Cross-reference its destination and separate the command from confirmation that the equipment responded.","terms":[{"name":"Input","meaning":"Auxiliary AC source"},{"name":"Output","meaning":"Control transformer primary"},{"name":"Application reference","meaning":"An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections."}],"diagram":"flow","steps":["Auxiliary AC source","CFI","Control transformer primary"],"caption":"A reading guide. The entry's original illustration and input/output facts describe this application.","sources":[{"label":"SEL-RPM redundant power module","url":"https://selinc.com/products/RPM/"}],"profileId":"power-installation-control-power"},"url":"https://eloragrid.ai/symbols/control-transformer-fused-primary-interface","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/control-transformer-fused-primary-interface.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pi26-station-power","publisher":"SEL","title":"SEL-RPM redundant power module","url":"https://selinc.com/products/RPM/","scope":"Independent AC and DC sources for station auxiliary power.","type":"manufacturer","checkedOn":"2026-11-03","reuse":"link-only","relevance":"Public technical context for switchgear control-power supervision. Independent AC and DC sources for station auxiliary power. The application text and educational graphic are independently authored; the publisher does not certify this representation."}]}