UL 845-2021 pdf download – Motor Control Centers.
3 Definitions 3.1 For the purposes of this standard, the following apply. 3.2 auxiliary devices – types of devices such as indicating meters (instruments), current transformers, control devices, control relays, timers, protective relays or protective devices, communications devices, etc. 3.3 available short-circuit current – the short-circuit current available at the equipment line terminals plus any motor contribution. The available ac short-circuit current is expressed in rms symmetrical A. 3.4 bus, horizontal – a bus that extends through a motor control center section. 3.5 bus, vertical – a bus that serves the units in a section and that originates from the horizontal bus. This bus may be replaced by insulated wiring. 3.6 Class I motor control centers – mechanical groupings of combination motor control units, feeder- tap units, other units, and electrical devices arranged in an assembly. (See Annex H). 3.7 Class II motor control centers 一a Class I motor control center provided with manufacturer- furnished electrical interlocking and wiring between units, as specifically described in overall control system diagrams supplied by the user. (See Annex H) 3.8 combination controller unit – a control unit containing a magnetic or solid-state controller and an externally operable disconnecting means and overcurrent protection. The controller may or may not contain motor overload protection. 3.9 combination motor control unit 一a control unit that contains components that perform the following functions: externally operable circuit-disconnecting means, motor branch-circuit overcurrent protection, motor overload protection, and motor control.
3.12 incoming supply conductor – a conductor installed to provide power to the equipment. 3.13 main bonding jumper 一the connection between the grounded circuit conductor and the equipment grounding conductor at the service. 3.14 motor control center – a floor-mounted assembly of one or more enclosed vertical sections typically having a horizontal common power bus and principally containing combination motor control units. NOTE Usually, units are mounted one above the other in the vertical sections. The sections normally incorporate vertical buses connected to the common power bus, thus extending the common power supply to the individual units. Power may be supplied to the individual units by bus bar connections, by stab connections, or by suitable wiring. 3.15 motor control center section – the vertical enclosure and assembly that is prevented by the structural framework from being physically separated into smaller parts and is intended to receive individual combination motor control units. The function of the vertical section is to support the horizontal and vertical buses, units, covers, and doors when the doors are not mounted directly to the unit. 3.16 service equipment – the necessary equipment, usually consisting of a circuit-breaker or switch and fuses, and their accessories, located near the point of entrance of supply conductors to a building or other structure, or an otherwise defined area, and intended to constitute the main control and means of cut-off of the supply. 3.17 system bonding jumper – the connection between the grounded circuit conductor and the equipment grounding conductor at a separately derived system. 3.18 Type A wiring – user (field) load and control wiring connected directly to device terminals internal to the unit (See Annex H.)