New control cabinet conceals busbars

Problem: Motor control centres either contain switching and control gear in separate enclosures, or mounted together on busbars in wardrobe-sized enclosures. The problem with mounting units in separate enclosures is that they take up a lot of space, incurring significant build costs, as well as costing more themselves. The problem with mounting them together is that, in the UK at least, it is necessary to switch everything off before attempting to test or change units, because of the live busbars. Solution: Rockwell Auto-mation has come up with a cabinet-based system which conceals the busbars behind plastic backs which remain attached. The system, designated Allen-Bradley 141A, allows switchgear and control units to be ‘clicked’ on and off by inserting a screw driver to release catches. Micro-switches beneath units de-energise contactors upon removal. Modules may be connected to control circuits with quick disconnect connectors. These are normally top mounted to keep control cabling separate from motor cabling on the output side. The result is a clean and EMC-favourable layout. Applications: The system comprises direct-on-line, reversing, star-delta and soft starters and PowerFlex AC drives. Maximum current rating is 125A and it conforms to Form 2B BS/EN 60439-1. All components are type tested according to BS/EN 60947, providing a partially type-tested switchgear and contol gear assembly in compliance with BS/EN 60439. The system has the highest form of protection against short circuits and has been tested to 50kA. Busbars are spaced at 60mm centres and may be either horizontal or vertical. TS