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The miniaturization of motor drives: Why and how?

The miniaturization of motor drives: Why and how?


All information and opinions presented in this paper are the authors. Design News online did no editing or confirmation of the information provided.

The emergence of a fast-growing market for micro drives is due, in large part, to a strong, sustained economy, domestically and internationally. With demand for both durable and non-durable products growing worldwide, corporate managers continue to re-engineer every part of their organizations -- from the receiving dock to customer-service delivery systems -- to maintain profits; this requires maximum production from their manufacturing facilities, and creates pressure on their component, assembly and product vendors.

Maximizing a plant's real estate

Plant managers (our customers), in turn, restructure and reconfigure every square inch of the "real estate" under their care to increase throughput, output and quality, reducing labor and waste as much as possible in the process. Capital improvements focus not so much on expanding plant size as on wringing as much production as is mechanically and humanly possible from existing capacity.

Rapidly developing technology in electrics -- power electronics, process controls and plant-wide control systems -- helps managers reach this objective. With their factory space at a premium, it pays these end users to scrutinize details, such as the size of control cabinets and panels. Witness micro drives for motors.

Micro drives are physically smaller, i.e., packaged in much smaller enclosures -- but they provide a full feature package, in many cases, identical to their larger counterparts. Micro drives currently offer a comprehensive range of performance/control options -- from simple motor starter control with communications to a sophisticated fully programmable motor drives. Manufacturers and end users describe this new physical reality as "power per cubic foot" or, even, "power per cubic inch," -- that is, getting maximum horsepower/control/usage out of every inch of cabinet space.

Freeing up physical and panel space

Consider the concept in a real-life application. Bottling company X is expanding its existing fill and cap lines to increase production, and the wider lines require using some of the space taken up by the existing control room. In this retrofit installation or a similar one requiring a multiple number of drives, the smaller drive/enclosure footprint becomes extremely important -- critical, both from the plant manager's and the drive manufacturer's point of view. Packaging of the entire motor drives system must fit into less space, without sacrificing any operating advantages. Similarly, when plants upgrade their electronics/process controls, the existing controls need to be consolidated to free up space. The micro drive manufacturer, in these instances, enjoys a distinct selling advantage.

The same is true in OEM applications where drives are components of large stand-alone machines (pumps, for example). Micro drives free up space to the machine designer -- physical space the OEM can utilize to increase capacity/output, or use to add in additional featuresbenefits; and panel space to which the OEM can add more electrical and mechanical controls.

Technology fuels miniaturization

How did drives get smaller? Primarily through different technologies galloping forward at the same time. Surface-mount technology has led the way, with its primary objective being the shrinkage of the components -- such as microprocessor and memory -- and, thus, the circuit boards used inside drives, while maintaining, even increasing, the capacity, speed and operation at which these components work. We've just begun, in fact, to see this miniaturization process at work for drives; look for the trend to continue and drives to shrink further as new materials and designs get married together by the component designers.

Micro drives also are possible as the result of continued improvement in heat-sink design. (Power modules instead of individual power components have saved heat sink space.) Small-dimension heat sink designs and the latest IGBT technology require increasingly less space, while offering the same heat dissipation capability.

Advancements in power electronics help, too. Within the last two variable-speed AC drives ABB has introduced, the ACS 600 and ACS 300, power electronics improvements include incorporating the inverter bridge into the IGBT device, as well as integrating temperature sensors; and reducing the number of protection components. ("Integration" and "reduction" are watchwords for consolidation and physical down-sizing of the electronic components, which, inch for inch, become more superior with virtually every subsequent drive introduction.)

It is the fusion of all these technologies that aid in producing ever-smaller drives, while improving performance, increasing reliability (through fewer parts and connections), and providing better noise immunity.

Future drive designs?

Where does this leave designers and manufacturers of drives? From an end user's point of view, micro drives make it possible, literally, to "get more from less": more performance; greater horsepower. Micro drives offer a good price-to-performance ratio, too -- a benefit that increases further in applications where there are spatial constraints. Drives with a shrinking footprint will make them a good choice for solving a host of challenges in a very wide range of industrial installations. So packing high-tech features in the smallest possible package provides an increasingly competitive edge in drive quoting, at least to the manufacturers producing them! Those manufacturers that are not will be forced to concentrate on designing superior large-frames drives only; or choose to develop and add micro drives, if they want to be a competitive one-stop, full-line provider to the market.

If you want to contribute a technical paper, please send a hard copy and IBMelectronic format (.txt file, .jpg file, or .gif file only). For more information, e-mail [email protected].
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