{"schemaVersion":1,"slug":"motor-generator-set","name":"Motor-generator set","kind":"symbol","abbreviation":"MG","aliases":["MG set","rotary converter","rotary frequency converter"],"category":"microgrid-systems","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEC","IEEE / ANSI"],"summary":"A motor mechanically coupled to a generator, used to isolate, change frequency or convert between AC and DC.","description":["A motor-generator set is an electric motor driving a generator on a common shaft. It provides complete electrical isolation, conversion of frequency or voltage, or AC to DC conversion, and its rotating mass rides through short disturbances. Some sets add a flywheel or an engine on the same shaft for backup.","Drawings show two machine circles, one marked M and one marked G, joined by a mechanical coupling line. The motor input and generator output are on separate circuits, each with its own protection and earthing.","Efficiency is lower than a static converter and the rotating machines need maintenance, so motor-generator sets are now mainly found in legacy, test or special-purpose installations. The symbol does not show speed, coupling arrangement or ride-through time."],"readingNotes":["The coupling line shows a mechanical link, not an electrical one.","Earthing of the generator output is independent of the motor supply."],"drawingChecklist":["State motor and generator ratings.","Show output earthing and protection.","Reference flywheel or engine if fitted."],"distinction":"A motor-generator set converts through rotating machines; a static frequency converter uses power electronics.","facts":[{"label":"Machines","value":"Motor and generator on one shaft"},{"label":"Isolation","value":"Complete electrical separation"},{"label":"Ride-through","value":"From rotating inertia"},{"label":"Preview","value":"Independent educational illustration; consult the applicable standard and project legend for the exact graphic"}],"references":[{"sourceId":"ieee-315","relevance":"Graphic-symbol standards context for rotating machines."},{"sourceId":"autodesk-generators","relevance":"Public generator symbol family context."}],"related":["static-frequency-converter","88-auxiliary-motor-or-motor-generator","rotary-ups","generator"],"artwork":"s28-motor-generator-set","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Motor-generator set mean?","introduction":"A motor-generator set is an electric motor driving a generator on a common shaft. It provides complete electrical isolation, conversion of frequency or voltage, or AC to DC conversion, and its rotating mass rides through short disturbances. Some sets add a flywheel or an engine on the same shaft for backup.","example":"Drawings show two machine circles, one marked M and one marked G, joined by a mechanical coupling line. The motor input and generator output are on separate circuits, each with its own protection and earthing.","drawings":"Efficiency is lower than a static converter and the rotating machines need maintenance, so motor-generator sets are now mainly found in legacy, test or special-purpose installations. The symbol does not show speed, coupling arrangement or ride-through time.","terms":[{"name":"DC","meaning":"Direct current: electricity flowing in one direction."},{"name":"AC","meaning":"Alternating current: electricity whose direction changes periodically."},{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."}],"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":"IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams","url":"https://standards.ieee.org/ieee/315/515/"},{"label":"Generator symbol variants","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-09BE3BB5-9118-4302-8061-3888692E538F.htm"}],"detail":"A motor mechanically coupled to a generator, used to isolate, change frequency or convert between AC and DC. A motor-generator set converts through rotating machines; a static frequency converter uses power electronics.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/motor-generator-set","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/motor-generator-set.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"ieee-315","title":"IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams","publisher":"IEEE Standards Association","url":"https://standards.ieee.org/ieee/315/515/","type":"standard","scope":"Graphic symbols and designation letters. IEEE lists this edition as Inactive-Reserved; it is a historical reference, not a claim of current compliance.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Graphic-symbol standards context for rotating machines."},{"id":"autodesk-generators","title":"Generator symbol variants","publisher":"Autodesk","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-09BE3BB5-9118-4302-8061-3888692E538F.htm","type":"cad-reference","scope":"DC and three-phase synchronous generator categories.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public generator symbol family context."}]}