Rockwell Automation Publication 2100-IN012D-EN-P - September 2010
9
Chapter
1
General Information
General Description
Allen-Bradley CENTERLINE Motor Control Centers (MCCs) consist of one
or more vertical sections containing electromagnetic or solid state control devices
that are prewired and tested within modular (plug-in) or frame mounted (hard-
wired) units.
CENTERLINE MCCs are designed in standard widths of 20 in. (508 mm), 25
in. (635 mm), 30 in. (762 mm), 35 in. (789 mm), and 40 in. (1016 mm). The
standard front-mounted depths of an MCC are 15 in. (381 mm) and 20 in.
(508 mm), in addition back-to-back mounted depths of 30 in. (762 mm) and
40 in. (1016 mm) are also offered. The standard height of an MCC is 90 in.
(2286 mm). A 70.5 in. (1791 mm) high section is also available. All MCC
sections are supplied with top and bottom horizontal wireways. Sections that are
designed to accommodate plug-in units include a vertical wireway. Each 90 in.
(2286 mm) vertical section can accommodate up to 6.0 space factors or 78 in.
(1981 mm) for units.
Units (buckets) are designed in increments of 0.5 space factors. Each 0.5 space
factor is approximately 6.5 in. (165.1 mm) high. Units are designed as either
removable (plug-in) or frame-mounted (non-plug-in).
Individual units house a wide variety of power and logic devices. Plug-in units are
mounted on unit support pans within the section. Stab assemblies on the back of
the unit plug onto the vertical bus. A mechanical interlock prevents the unit door
from being opened when the disconnect is not in the OFF position. An
additional mechanical interlock prevents the unit from being plugged-in or
unplugged when the disconnect is not in the OFF position.
Line power is distributed throughout the MCC via an isolated bus work
structure. The main horizontal bus is in the center of each section. Standard,
center-fed, 300 A rated vertical bus supplies power to the individual units above
and below the horizontal bus for an effective 600 A capacity, allowing virtually
unrestricted unit arrangement. An optional 600 A vertical bus provides 1200 A
effective rating.
The CENTERLINE MCC is also available with an ArcShield rating. The
ArcShield rating includes arc-resistant features that are intended to help provide
enhanced protection to you during internal arcing faults (when compared to
MCCs that are only designed to meet UL 845 requirements). Arcing faults can
be caused, for example, by accidental touching, closing into faulted lines, or loose
connections. Depending on the application, MCCs with the ArcShield rating can
provide up to Type 2 accessibility per IEEE standard C37.20.7, which helps
protect you when you are at the front, sides, and rear of the enclosure in the
unlikely event of an arcing fault.
