Electronics Protection - March/April 2013 - (Page 12)

Feature Increasing the Lifespan and Reliability of Electrical Components Bruce Kreeley, Director of Sales and Engineering Steve Coulton, the Business Development Manager Kooltonic Heat is both a by-product and one of the greatest enemies of electrical and electronic components. If not dissipated, this heat has the potential to cause early failures and malfunctions. Components commonly packaged in electrical enclosures, computer server racks, and other product compartments are the vital controls for drives and displays used in many industries including telecommunications, industrial automation, machine tools medical instrumentation, retail kiosks, security imaging and detection equipment, robotics, etc. The primary purpose of these electrical enclosures is to provide protection and safety for the components they house. If an enclosure is properly cooled, the components within can have a long and useful life. Without proper cooling, however, the components in these enclosures can be subject to damaging heat, shortening their longevity and reliability. Although individual manufacturer’s specifications vary, the majority of electrical distribution and control equipment is designed to operate properly and achieve normal life expectancy under ambient air conditions ranging from 40°C to 50°C (104°F to 122°F). The table below indicates the maximum operating temperatures for specific devices. It is generally accepted that operating temperatures above this range reduce life expectancy. Every ten degree rise in temperature shortens the average reliability of electrical/ electronic components by 50 percent. Table 1 shows examples of components typically found in electrical enclosures. Table 1 Based on the information provided in Table 1, it is clear that thermal management is advantageous. Reducing the operating temperatures within electrical enclosures is an effective way to increase life expectancy and system reliability. If an enclosure is properly cooled, the cost associated with that cooling can be recovered over the life of the equipment. The graph opposite, “Drive Life Increase with Reduction of Enclosure Temperature” illustrates the benefits of increased longevity when a drive enclosure is cooled properly. This is based on typical drives having a 40°C (104°F) maximum recommended environmental temperature. The Sources of Heat The primary source of heat production in an electrical enclosure is from the working components. Devices that transmit motive power have voltage drop or efficiency losses that are converted into heat. In the case of electronics or microprocessors, nearly all of their power is converted into heat. The means for calculating and estimating this heat generation are available from enclosure cooling manufacturers in the form of spreadsheets or calculators. 12 Heat gain or loss is expressed in watts or BTU’s (British Thermal Units). These units of heat are converted as follows: Watts = BTU / hr. ÷ 3.414 and BTU/hr. = Watts x 3.414. This internal heat load is one source that will cause the internal enclosure temperature to rise to unacceptable levels if it is not removed. Ambient Air Ambient air, which is the air outside the enclosure, can also be a potential source of heat gain. The ambient air may be cool enough to allow the enclosure to dissipate heat, however, in many cases ambient air may be so hot that it adds to the heat load. Solar Load When enclosures located outdoors are exposed to the sun, heat will be transferred to the inside of the enclosure. This is known as solar load or solar gain. (The effects of solar load can be significant; an automobile parked outdoors on a sunny day is a prime example.) Thermal insulation, white reflective paint finishes and a roof or sunshield will often help to offset solar load. Some enclosures are double walled for this purpose. However, this tends to be a very costly process. Humidity and Air Infiltration Outside air entering an electrical enclosure carries both heat and humidity. High relative humidity in the air potentially increases the heat content. In most cases it is best to seal the enclosure to limit this effect. Condensing water vapor or the formation of dew from high humidity, particularly in outdoor enclosures will damage the electrical and electronic contents of an enclosure. It is best to seal up enclosures and feeding conduits completely to avoid this type of heat gain and effects of humidity. Removing the Heat Heat transfer by natural convection is the simplest and most common method of cooling electronics. Relying entirely on hot air rising, however, is generally not sufficient to safely cool sensitive electronics and electrical power transmitting components. Often natural convection is used in conjunction with a heat sink to keep electronics cool. An electronic component mounted on a heat sink helps cool the electronics by dissipating heat into the air. Such passive thermal management solutions are found in consumer March/April 2013 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - March/April 2013

Electronics Protection - March/April 2013
Newer Technology Releases Next-Generation Power2U AC/USB In Wall Charging Solution
Specifiers of Enclosures for Components in Outdoor Applications: Be Aware of Material Selection Issues
How to Protect Electronic Circuits from Power Surges
Testing for Ingress Protection of Portable Electronic Devices
Increasing the Lifespan and Reliability of Electrical Components
From the Inside: The Configurable Plastic Enclosures Revolution
Tips for Selecting and Designing a Membrane Switch
HP Intelligent Series Rack Models Available for Networking and Demanding Server Requirements
Polyonics Antistatic Tapes Solve ESD Problems Before They Damage Static Sensitive Devices
OptoTherm Introduces IR LabMate Infrared Camera Solution
Falcon Electric Offers NEMA 3R/4 Enclosures with SSG UPSs
PEM SpotFast Fasteners Enables Flush Joining of Two Sheets
Industry News
Calendar of Events

Electronics Protection - March/April 2013