Rockwell Automation 294D ArmorStart LT Distributed Motor Controller DeviceNet Version - User Manual - Manual (Page 189)

Rockwell Automation Publication 290D-UM001A-EN-P - June 2012 189
Appendix
A
Applying More Than One ArmorStart LT
Motor Controller in a Single Branch Circuit
on Industrial Machinery
Introduction Each ArmorStart LT motor controller is listed for group installation. This
appendix explains how to use this listing to apply ArmorStart LT motor
controllers in multiple-motor branch circuits according to 7.2.10.4(1) and
7.2.10.4(2) of NFPA 79, Electrical Standard for Industrial Machinery.
From the perspective of the ArmorStart LT product family, being listed for group
installation means one set of fuses or one circuit breaker may protect a branch
circuit that has two or more of these motor controllers connected to it. This
appendix refers to this type of branch circuit as a multiple-motor branch circuit.
The circuit topology shown in
Figure 40 , is one configuration, but not the only
possible configuration, of a multiple-motor branch circuit. In these circuits, a
single set of fuses (or a single circuit breaker) protects multiple motors, their
controllers and the circuit conductors. The motors may be any mixture of power
ratings and the controllers may be any mixture of motor controller technologies
(magnetic motor controllers and variable-frequency AC drive controllers).
This appendix addresses only NFPA 79 applications. This is not because these
products are only suitable for industrial machinery, but because industrial
machinery is their primary market. In fact, while all versions of the ArmorStart
LT products may be applied on industrial machinery, the versions that have
the Conduit Entrance Gland Plate Option may also be used in applications
governed by NFPA 70, National Electrical Code (NEC), (see “ArmorStart LT
Product Family”).
In the 2012 Edition of NFPA 79, motor controllers that are listed for group
installation may be installed in multiple-motor branch circuits according to either
of two alternative sets of requirements. The first is found in 7.2.10.4(2), the
second in 7.2.10.4(3). The requirements of 7.2.10.4(3) are similar to those in
430.53(C) of NFPA 70, while the requirements of 7.2.10.4(2) are found only in
NFPA 79. This appendix explains the requirements of 7.2.10.4(2), rather than
those of 7.2.10.4(3), because this is the simpler method to use when applying the
ArmorStart LT family of motor controllers.
The user must determine the requirements – NFPA 79 or NFPA 70 – to use for
the application. When making this determination, it is necessary to understand
the ArmorStart LT product characteristics and useful to understand the
definition of industrial machinery. The section of this appendix, “ArmorStart LT
Product Family”, specifies whether a motor controller is suitable for installation
according to NFPA 79 or NFPA 70 (or both). The definition