• • • ENCLOSURES • • •


Key factors to consider when selecting cabinets for 19in mounted electronic equipment


Alan Vincent, sales director of Foremost Electronics, recommends designers and systems integrators take into account the following seven key considerations when considering the selection of a suitable cabinet


S


electing a suitable cabinet for any electronic system can be a challenge. Applications and environmental conditions are major


influences on sourcing the correct product. Other than the large 19in datacomms and telecoms markets and clean room or laboratory use, cabinets may be required to withstand or protect the installed equipment from extreme heat, high dust or other contaminant environments, radio- frequency/electromagnetic interference (RFI/EMI) and locations subject to high shock and vibration. To help select the best possible 19in


electronics cabinet solution for a specific application this article outlines seven essential design considerations.


Design Standards Depending on the end system requirements, meeting appropriate design standards may be necessary. Standards for equipment safety and EMC compatibility are created and imposed by worldwide associations, government agencies and regulators.


Standards result from technical agreements


related to design specifications and environmental requirements that need to be fulfilled by a product or service. Some key design standards associated with electronics cabinets include the following:


IEC International Electrotechnical Commission (IEC) develops international standards for all electrical, electronic and related technologies. Adoption is voluntary, although they are often referenced in mandatory national laws or regulations worldwide. IEC 60297 (mechanical structures for electronic


equipment – dimensions of mechanical structures of the 19in series) standard provides crucial information for designing 19in cabinets – IEC 60297; IEC 60297-3-100 (19in Standard); IEC 60917- 2-2 (25mm metric Standard); ETS 300 119-2/-3 (European Telecommunication Standard)


RoHS Compliance Restriction of Hazardous Substances. (RoHS), originated in the European Union and restricts the


use of six hazardous materials found in electrical and electronic products.


MIL-S-901D This is a specific military test requirement designed for shipboard applications. Based on the type of equipment – essential or non-essential to the safety and combat-readiness of the ship – qualification testing is performed on a specified machine placed on a barge floating in a pond where explosive charges are detonated at various distances and depths in the pond to impart shock upon the equipment.


Cabinet Dimensions 19in cabinets provide a standardised frame or enclosure for mounting various types of electronic equipment. Each piece of equipment is typically 19 inches (482.6 mm) wide, including edges or mounting ears, which allow for mounting to the rack frame. Cabinet height is defined in “Units” (U), each unit equals an industry standard of 1.75 inches (44.45 mm). Rack-mountable equipment is usually designed


to occupy a specified number of “U”. Cabinet depths may vary depending on the application, typical depths range 600-1200mm. Detailed guidance regarding mechanical structure standards for 19in electronics may be referenced in IEC 60297-3-100.


Weight load capacity The amount of weight loaded into a cabinet can vary widely, it is therefore very important to consider this factor to determine the correct type of cabinet for a specific application. Whether it is to contain several banks of batteries for uninterruptable power supplies, or an array of hard drives in a datacentre, proprietary equipment or other heavy components, underestimation of weight loading requirements is a very common concern for engineers. It is especially difficult because some tests may


be conducted to ensure optimal results, such as mounting the heaviest equipment at the bottom of the cabinet, which may not correspond to the layout in the final application. Working with heavy loads can also present other


issues. Depending on the application, some cabinet designs may require dynamic protection, which in turn, necessitates a more robust design depending on the load.


22 ELECTRICAL ENGINEERING • OCTOBER 2022 electricalengineeringmagazine.co.uk


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