How to combine design options for best resultsElectrical/electronic enclosures/boxes contain components that naturally generate heat.Therefore, electrical engineers must take care to select the most suitable solutions to maintain the temperature in an acceptable range.Existing cooling methods take heat from inside the case and transfer it to the outside, keeping the components inside below dangerously undesirable values.In what follows, we briefly present Emily Newton's conclusions.When engineers work with metal cases and backplanes, thermal conduction can help transfer component heat to the backplane and into the case.Through this process, heat generated inside an enclosure can reach the outside.However, if the outside air is extremely hot, thermal conduction alone is unlikely to provide the desired temperature-reducing effects.Another fundamental practice is to increase the size of the case, thereby providing a larger surface area for heat exchange.Furthermore, placing the components at greatest risk of overheating near the bottom of the case is a sensible design choice, as hot air rises, pushing cold air down [1].Installing a fan system could force evaporation or heat conduction through air movement.Furthermore, a venturi air cooling system could be used, which brings compressed air into the case.This setup requires the use of a thermostatically controlled valve that moves compressed air through the venturi and relies on a one-way valve to send internal air to the rear of the case.Addressing excessive indoor humidity is another effective solution.Humidity makes it easier for the air to retain heat.Thus, the decrease in humidity causes a cooling effect.The key thing to remember is that it's usually best to consider how different cooling methods work together to keep an enclosure at the desired temperature.What influences the temperature of the enclosure?Selecting the most appropriate approach to cooling a case also requires knowing the potential factors that cause heat levels to rise.Statistics indicate that every 10 degrees Celsius increase in temperature causes a 50% reduction in the reliability of electronic components [2].Maintaining an adequate temperature in an enclosure requires knowledge of what influences the associated heat.For example, a case in direct sunlight will heat up faster than one in a shaded location.Also, choosing a non-metallic material or opting to paint the case will produce better results than bare metal.Temperature issues can also occur if you don't use a dustproof case.The dust particles insulate the components so that they do not benefit from the full cooling effects of whatever method is used.If the environment inside the case / box is less than, approximately, 55 degrees Celsius, the cooling systems can be considered effective.However, users should take care to filter the outside air.When contaminants enter the casing, they could cause the head pressure of the condenser section to rise.If this occurs over a prolonged period, the conditions could cause premature failure of that part.In addition, all cooling systems require periodic maintenance.Alternatively, if you want a passive cooling system, heat pipes could provide the necessary thermal conductivity.Heat pipes can operate over an extremely wide temperature range, from -271°C to 2000°C [3].This is one of the reasons why they can be used in highly demanding applications such as those associated with spacecraft.Cooling systems used to control the temperature of electronic circuits typically consist of a copper heat pipe inside a copper jacket.Beyond cooling, customer requirements must be metCooling requirements are often just one line in a long list of a customer's needs.For example, a person may need a closet made with a hygienic design.If a food and beverage manufacturer wants an enclosure that houses electrical connections or systems, they may insist on an easy-to-clean design.Most enclosures for electrical systems that do not have hygiene in mind have numerous areas that could trap dirt.The same could happen with recessed surfaces or those with unrounded corners.Installing drain slopes for an enclosure helps drain water from it during cleaning.In addition to design principles that support hygienic conditions, engineers must determine which cooling method works best in environments that receive frequent cleaning.An air/water heat exchanger is a clean and frequently used choice.It is also a cost-effective solution due to low maintenance and low energy consumption [4].This example is meant to highlight that cooling methods cannot be taken out of context.The designer must take the time to determine what the customers' needs are.This usually precludes certain approaches to cooling systems.Design engineers then narrow down their options while taking a holistic view of customer needs.The specifications of the electronic components must be taken into accountWhen selecting the best cooling methods for cases, people must prioritize the sensitivity of the electronic devices inside.Fortunately, finding the right approach can go beyond just making a guess based on experience.There are references.NEMA (National Electrical Manufacturers Association) defines different grades for electrical enclosures in North America.Similarly, the IEC (International Electrotechnical Commission) sets ingress protection (IP) classes for enclosures.There are also UL (Underwriters Laboratories) protection classes.Steve Sullivan, training and development supervisor at Rittal North America, LLC, believes that electronic component specifications serve as starting points for selecting cooling methods.He stated: "Usually the specifications for these electronic devices will detail the cooling requirements and even the preferred type of enclosure in terms of degrees of protection such as NEMA, UL or IP.[5]"“In such cases, you have to adapt the climate control to those specifications.The case/case and the cooler will probably have to match in terms of protection class.For example, if you have a NEMA 4 enclosure and you put a NEMA 12 filter fan on it, then the panel will step down to NEMA 12,” he continued.There is no single best methodThis overview points out that there is no universally superior option for cooling electrical enclosures/boxes.Selecting the most appropriate options requires evaluating many factors, including the average ambient temperature, a component's specifications, and any needs associated with a customer's industry.Considering the combination of influences helps prevent unexpected consequences and stop premature failure of temperature-sensitive parts.Below are some examples:The present example is part of the Aurocon COMPEC offer of housings for voltage sources.Power supply enclosures are robust and have been specially designed to house transformers and other components in a safe manner.Some power supply enclosures include brass ground pins or pins for connecting a power supply.Power supply enclosures are available in a multitude of sizes, depending on the components they need to house.They are popular in most industries because of the safety features they offer:The exemplified product is a sheet steel housing / box with an integral rail system for mounting various products.Excellent corrosion protection and powder coated surface with high abrasion resistance.Cooling fins for optimal heat extraction.Integral crane eyes for larger models, legs for smaller models.Dual sleeves for connecting cables.The size of the case is 130mm × 140mm × 170mm, it is made of steel, with protection class IP20.The example presented is part of Aurocon COMPEC's offer of general purpose boxes/cases, which do not have a specific destination, being created and designed to house and protect a wide range of equipment, mostly electrical / electronic.The type of case you choose depends entirely on the application you are using it for.The range of general purpose enclosures features a variety of different materials such as aluminium, plastic and fiberglass, some of which are reinforced, flame retardant and corrosion free.Aluminum housings are available in a variety of types, such as aluminum alloy and die-cast aluminum.The classification of casings / boxes can also be done according to: materials for gaskets;dimensions;different IP protection classes such as IP65, IP54 and IP66;variety of colors;options with mounting flanges;some of the cases have ventilation, display windows and chassis mounting plates.The exemplified box/housing solution is fiberglass reinforced and consists of two parts.The base has M4 (Dodge) threaded inserts for attaching a mounting plate or mounting frame.The cover is made of opaque fiberglass reinforced polyester.The housing/box gives you security for both operators and equipment, with isolation and protection to IP 67 (IED 60529 and EN 60529).IK10 protection against external mechanical impacts (EN 62262 and IEC 62262).Designed for demanding environments, the enclosures are corrosion resistant and maintenance free, plus they are RoHS compliant.Wide Terminal Resistors Improving circuit reliabilityWide terminal resistors have been around for many years, and the best known benefit in using them is that the designer can dissipate more power into a smaller device because heat is dissipated more efficiently through the long side terminals.rather than on the short side.In what follows, we briefly present Paul Caston's conclusionsThe adjacent figure illustrates the dimensional difference between the two types of resistors, both rated at 0.75W @ 125°CThis means that the designer can use the former either to save PCB space or to increase the power in the circuit without having to use larger parts.However, there is a lesser known but still very important benefit in using wide terminal devices: reduced termination cracking after repeated thermal cycling.FR4 PCBs have a coefficient of thermal expansion of about 17 ppm/°C, while the ceramic substrate of the resistor has one of about 5 ppm/°C.In many applications this difference does not matter, but if the designed device is expected to withstand repeated, rapid cycling of temperature variations, then the possibility of terminal cracking may arise.The adjacent image shows a terminal crack of a standard size 1206 resistor subjected to more than 2500 rapid temperature cycles on a standard FR4 PCB.The greater the distance between the terminals, the greater this stress on the solder.So this means that resistors with larger case sizes are more affected than smaller devices.The most obvious way to reduce mechanical stress is to reduce the size of the resistor used, but this is not always possible if the device has to dissipate some power.Switching to a resistor with wide terminals has two benefits in this regard.First, the terminals are much longer, which means that if a crack occurs, the integrity of the solder joint will last longer.Second, as we can see from the image above, the terminals are closer.In this example, 1 mm versus 3.7 mm.A slight disadvantage of using wide terminal resistors is the resistance value.The maximum resistance value of the WK73 series is 1M, while the RK73 is available up to 10M.Ranges available from RS include the WK73R series and the WK73S seriesThe KOA WK73S series are surface mount thin film resistors in the 1020 capsule with ±1% tolerance and 3.3Ω resistance.The rated power of the resistor is 1W and the temperature coefficient is ±100ppm/°C.Tin (Sn) is used as the terminal material.The resistor has an overload of 400V and an operating voltage of 200V.Among other features can be highlighted: wide terminals, high operational safety and performance with TCR ±100×10−6/K, an operating temperature range from -55°C to 155°C.Author: Bogdan Grămescu Aurocon Compec https://www.compec.roYour email address will not be published.Required fields are marked *Save my name, email and website in this browser for the next time I comment.