MCC design: have you considered Form 2?

24Aug

Businesses should seek out the cost and operational benefits to be gained by adopting Form 2 motor control centre design, says Mark Harrison, who believes that Form 4 could well be an unnecessarily expensive method of MCC design, given the belt-tightenings that most enterprises are currently undergoing

With current economic conditions challenging many enterprises – particularly those in the manufacturing sector – most are now looking at ways of reducing costs, while at the same time increasing operational efficiencies. Industrial processes and manpower levels may be reviewed to see where cost can be squeezed out, but one area common to all production facilities can offer immediate potential for savings.

Low voltage motor control centres (MCC) are at the heart of most manufacturing plants where they distribute power to, and provide control of, the many electric motors installed across such facilities. Usually an assembly comprising one or more enclosed sections, they have a common power bus and house all necessary motor control devices such as contactors, soft starters, variable speed drives and programmable controllers.

MCCs are critically important installations as they have command of the entire motor architecture of a factory or plant; hence the associated time and cost considerations of any MCC development and installation are important factors when looking at the overall cost and effectiveness of the production process.

Form factors
MCC panels are available in different types, according to the complexity of the systems they are required to control. The simplest is an ‘open wardrobe’ type panel (Forms 1 and 2), while Forms 3 and 4 refer to compartmentalised panels where different aspects of a process have to be physically separated to allow individual control and isolation.

Traditionally, the design and build of the MCC has been based upon the long-established Form 4 approach. The philosophy behind this is ingrained via the principle of ‘separation’ which is overseen by British Standard EN 60439-1. It states that Form 4 assembly should, for instance, provide ‘separation of busbars from the functional units and separation of all functional units from one another, including the terminals for external conductors which are an integral part of the functional unit’.

And while this approach has underpinned the development of many historic MCC applications, it could be argued that the time has now come for panel builders and end users alike to embrace the commercial and industrial advantages inherent in Form 2 design and assembly.

Form 2 seeks separation of busbars from the functional units, but terminals for external conductors do not need to be separated from the busbar itself. Adopting Form 2 could lead the way to substantial cost and space savings for end users, as well as enabling panel builders to deliver MCC panels to market more quickly and more competitively.

While Form 4 is still heavily specified in many industries as the traditional way to build LV motor control centres, it could be said that the very separation provided by a Form 4 style enclosure is actually provided by the modern design of the internal devices themselves. This was not the case when the first MCCs appeared in the 1950s on car production plants.

While this separation point can be debated, nonetheless, it is worthy of serious consideration and Form 4 could well, in the current marketplace, be an unnecessarily expensive method of MCC design that could compromise a company’s ability to take advantage of modern control gear technology and innovation.

Manufacturers of LV control gear spend huge sums annually on product innovation, not just to gain a competitive market advantage for themselves, but also to save costs for panel builders and, ultimately, their clients. As a result of this investment, modern control gear now allows the provision of many individual motor starters in increasingly smaller footprints, largely due to miniaturisation, modularity and reduced wiring requirements.

But innovation that allows for vastly reduced MCC cabinet size and the associated benefits this delivers are, in essence, lost if remaining with Form 4 assembly, where each individual starter requires its own compartment.

Another advantage of Form 2 is that it represents a more environmentally-friendly approach to MCC design. Clearly, a tangible benefit of being able to specify smaller cabinets is reduced raw material consumption and even less in terms of transportation – both of which contribute to a more sustainable design methodology.

Form 2 to the fore
The fairly recent introduction of Form 2 and its increasing popularity has a positive impact on new factory construction, as well as those facilities undergoing retrofits and upgrades. Form 2 provides access to smaller sized panels with direct cost savings in terms of reduced cabling, materials, installation and labour. Smaller panels also mean lower civil engineering costs.

For any manufacturing business looking to cut costs without reducing their operational efficiencies, as well as MCC panel builders wanting to get to market more quickly, adopting Form 2 MCC panel design methodology really is a win-win situation.

Mark Harrison is with Siemens Industry Automation and Drive Technologies