Form A Queue

7th November 2012
Source: Siemens
Posted By : ES Admin
Form A Queue

Businesses should seek out the cost and operational benefits to be gained from Form 2 motor control centre design. Mark Harrison, Product Specialist with Siemens Industry Automation and Drive Technologies, discusses the costs and benefits of MCC's against the backdrop of the current ecenomic climate in this article from ES Design Magazine.

With the current challenging economic climate as a backdrop, companies – particularly in the manufacturing and production sectors - are continually looking at methods to reduce costs and at the same time increase operational efficiencies. Whilst processes and manpower requirements within commercial or industrial applications can be examined to see where to squeeze out costs, one key area that is intrinsic to production capability offers a simple and effective route to expenditure savings and speedier application.

Low voltage motor control centres (MCC) form the basis of any industrial application, and are used to centralise the distribution of power and control to the electric motors utilised in manufacturing and production across all sectors - from car production plants to the process industries and beyond. Usually an assembly of one or more enclosed sections, they have a common power bus and contain motor control units. A motor control centre can include variable frequency drives, programmable controllers and are used for low voltage three-phase alternating current motors from 230V to 600V.

As a key element in powering and controlling the motor architecture in a factory or plant, the associated time and cost considerations of any MCC development and installation are important factors when looking at the overall cost and effectiveness of production processes.

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’.

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This long-held approach has underpinned the development of many historic MCC applications. However, it could be argued that the time has now come for panel builders and end users alike to more proactively embrace the commercial and industrial advantages inherent in Form 2 design and assembly.

Cost savings

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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 offering a far more flexible solution to enable panel builders to deliver MCC panels to market in less time, as well as more competitively.

While Form 4 is still heavily specified in many industries as the traditional way to build low voltage 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 innovation.

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Each year, huge sums of research and development investment is spent by manufacturers of low voltage control gear to generate innovative methods that can allow their products to gain a competitive market advantage and save the electrical panel builder money. As a result, modern control gear now allows the provision of many individual motor starters in an increasingly smaller amount of space - thanks to radically reduced physical sizes, modular concepts and reduced wiring requirements. Such innovation that allows for vastly reduced MCC cabinet size and the associated benefits it delivers are in essence lost if remaining with Form 4 assembly, as in such cases each individual starter requires its own compartment.

Another added advantage of Form 2 is its basis as a greener solution. A tangible by-product of manufacturing smaller cabinets is the reduced use of raw material sources in the form of steelwork and even less transportation – both aspects contributing to a more sustainable future.

The fairly recent introduction of Form 2 and its increasing use is an important development for new factories being constructed today, as well as those undergoing retrofitting projects. Form 2 provides access to smaller sized panels with direct cost savings in terms of reduced cabling, installation and labour. Smaller panels can also contribute directly to lower civil engineering costs, with less space required to house the units, meaning overall building design can take this important (and costly) factor into account at planning stages. As an example, if the requirements of the water industry can be met through the construction of reduced sized houses for smaller MCCs, then significant sums in terms of civil engineering can be saved. Likewise, the particular need of the food and beverage industry - which necessitates that all MCC panels have to be produced in stainless steel for hygiene purposes - can also be tackled as the resulting lower amount of steel use provides cost benefit to the bottom line.

From an operational viewpoint, the MCC panel components themselves are vastly improved via the Form 2 approach. With increased integration possible with system control and innovative diagnostics providing a route to fast problem solving and fault finding, the operational efficiencies associated with, for example, preventative maintenance strategies are clear. With easier to swop components reducing plant downtime markedly, plant production effectiveness can be impacted positively.

For the modern production business looking to make inroads into spiralling costs without reducing their operational efficiencies and MCC panel builders wanting to get to market more quickly, adopting the methodology of Form 2 MCC panel design really is a win-win situation.


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