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{{Short description|Assembly to control a series of electric motors from one location}}
[[File:Motor Control Center 480 Volt.jpg|thumb|A small, early 1960s-vintage motor control center for 480 volt motors.]]

A '''motor control center''' ('''MCC''') is an assembly to control some or all [[electric motor]]s in a central location. It consists of multiple enclosed sections having a common power bus and with each section containing a combination starter, which in turn consists of [[Motor soft starter|motor starter]], [[Fuse (electrical)|fuse]]s or [[circuit breaker]], and power [[disconnector|disconnect]].<ref name="eep">{{cite web|title=Siemens Basics of Motor control centers|url=http://electrical-engineering-portal.com/res/Siemens-Basics-of-Motor-control-centers.pdf|website=electrical-engineering-portal.com|publisher=EEP - Electrical Engineering Portal|accessdate=29 May 2018}}</ref> A motor control center can also include push buttons, indicator lights, [[variable-frequency drive]]s, [[programmable logic controller]]s, and metering equipment. It may be combined with the electrical service entrance for the building.<ref name=NEC100Definition>{{Cite book | author=National Fire Protection Association | title= NFPA 70 National Electrical Code | access-date=October 9, 2023 | year=2017 | publisher=NFPA | location=1 Batterymarch Park, Quincy, Massachusetts 02169 |url=https://archive.org/details/gov.law.nfpa.nec.2017/gov.law.nfpa.nec.2017/page/n42/mode/1up | chapter=Article 100 Definitions | quote=Motor Control Center: an assembly of one or more enclosed sections having a common power bus and principally containing motor control units.}}</ref>

MCC's are typically found in large commercial or industrial buildings where there are many electric motors that need to be controlled from a central location,<ref name="eep"/> such as a [[mechanical room]] or [[electrical room]].

==Voltage ranges==
Motor control centers are usually used for low voltage [[three-phase]] alternating current motors from 208 V to 600 V. Medium-voltage motor control centers are made for large motors running at 2300 V to around 15000 V, using vacuum contactors for switching and with separate compartments for power switching and control.<ref>Robert W. Smeaton (ed) Switchgear and Control Handbook 3rd Ed., Mc Graw Hill, New York 1997 {{ISBN|0-07-058451-6}}, chapter 26</ref>

==Usage==
Motor control centers have been used since 1950 by the automobile manufacturing industry which used large numbers of electric motors. Today they are used in many industrial and commercial applications. Where very dusty or corrosive processes are used, the motor control center may be installed in a separate air-conditioned room, but often an MCC will be on the factory floor adjacent to the machinery controlled.

==Components==
A motor control center consists of one or more vertical metal cabinet sections with power bus and provision for plug-in mounting of individual motor controllers. Very large controllers may be bolted in place but smaller controllers can be unplugged from the cabinet for testing or maintenance. Each motor controller contains a contactor or a solid-state motor controller, overload relays to protect the  motor, fuses or a circuit breaker to provide short-circuit protection, and a disconnecting switch to isolate the motor circuit. Three-phase power enters each controller through separable connectors. The motor is wired to terminals in the controller. Motor control centers provide wire ways for field control and power cables.

==Specifications==
Each motor controller in an MCC can be specified with a range of options such as separate control transformers, pilot lamps, control switches, extra control terminal blocks, various types of thermal or solid-state overload protection relays, or various classes of power fuses or types of circuit breakers. A motor control center can either be supplied ready for the customer to connect all field wiring, or can be an engineered assembly with internal control and interlocking wiring to a central control terminal panel board or programmable controller.

==Fire protection==
Motor control centers usually sit on floors, which are often required to have a [[fire-resistance rating]]. [[Firestop]]s  may be required for cables that penetrate fire-rated floors and walls.

==See also==
* [[Power distribution center]]
* [[Transformer]]
* [[Switchgear]]
* [[Motor controller]]
* [[Power factor|APFC]]

==References==
{{Reflist}}

{{commons category}}

[[Category:Electric power systems components]]
[[Category:Electric power infrastructure]]
[[Category:Electric motor control]]