Cooling Power Supplies

Power supplies generate waste heat which has to be dissipated. They typically have either convection cooled or forced cooled ratings or, in some cases, both. Forced cooled power supplies may incorporate a cooling fan, or may specify the user cooling required to operate the unit at maximum load and ambient temperature.

Where user cooling is required it is most important that the power supply cooling is adequate for both safe operation and adequate service life. It is very application specific and dependent on the ambient temperature, applied load and physical location with respect to the cooling fan and other system assemblies.

The main difference between convection and force cooled products is in the power density offered. For a given efficiency, convection cooled products offer a lower power density, meaning that they occupy a larger volume. A power supply on a 3” x 5” industry standard footprint may have a convection rating of 150 W while the force cooled version may have a rating as high as 350 W.

Convection Cooling

Where the power supply has a convection cooled rating, it is intended to be used in an environment where there is free air. The system designer must ensure that there is adequate space around and above the unit for free air convection currents to cool the unit and must also ensure that the ambient temperature local to the power supply is controlled to a level within its maximum ratings.

Forced Cooling

Force cooled products with integral cooling fans are easy to apply as it is a simple matter of ensuring that the maximum specified ambient temperature is not exceeded for a given load rating and that the intake and exhaust areas are not obstructed.

Typically, power supplies that require the user to provide forced air cooling will specify a minimum required airflow. This is usually for operation at 100% of the power rating at the maximum ambient temperature allowed.

The required airflow is often specified in Cubic Feet per Minute (CFM) which is also the common rating for cooling fans. The effectiveness of cooling fans installed in enclosures must be given consideration, as discussed earlier in this section, and the CFM rating deals in volume of air rather than air speed, which is the important factor. The object is to maintain the components used within the power supply at a safe operating temperature and to ensure adequate service life.
When the required airflow is specified in CFM it assumes that the power supply is installed in an area which is relatively similar to it’s own cross sectional area. This is rarely the case as the power supply is typically used as a sub-assembly within a complete equipment enclosure. It will also assume that the air is directed at the power supply, which may also not be the case, so converting to Linear Feet per Minute (LFM) or meters per second (m/s) provides a more valid criterion as linear air speed measurements specify where the air is flowing and directly relate to heat transfer.


In the case above, the power supply requires forced air of 7 CFM in the direction indicated by the arrow. The cross sectional area is:-

3” x 1.43” = 4.29 inches2 or 0.0297 feet2

Therefore the air velocity required is:-

7/0.0297 = 236 LFM or 1.2 m/s

This air speed can be measured locally to the power supply to ensure that sufficient forced air cooling is being applied.Evaluation of the Application

The object is to maintain the components used within the power supply at a safe operating temperature and to ensure adequate service life. Given the huge potential for variation between one application and another, the only real test is measurement of the temperature of the critical components within the power supply assembly when installed within the end application under the worst case external ambient conditions. The other option is to model the application exactly using a suitable software simulation.

The criteria for safe operation will be specified for the power supply in question or can be obtained from the manufacturer. For the example above, the specific component temperatures for safe operation are given below; these are typical for a power supply of this type.


While these figures will ensure safe operation they do not give any indication of the service life that can be expected. The lifetime of a power supply is largely determined by the temperature of the electrolytic capacitors, which have a wear out mechanism. As a general rule, capacitor lifetime can be doubled for every 10 °C drop in operating temperature.The graph below indicates the expected service life of the power supply based on measurement of two key electrolytic capacitors.



Gary Bocock is a qualified electronics engineer and Member of the Institution of Engineering and Technology (MIET).

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Innovative Energies announced the EPL225 series of high efficiency open frame AC-DC power supplies.

Product news
Reference: EPL225



IE leads the industry with 95% efficient 225 Watt AC-DC supply in a 2” x 4” package

Innovative Energies today announced the EPL225 series of high efficiency open frame AC-DC power supplies approved for industrial, IT and medical applications. The series comprises seven single-output models that offer a range of standard output voltages from +12 VDC to +48 VDC.  A secondary 12 VDC / 0.5 A fan output is provided across the range. Packaged in an extremely compact low profile 2 x 4 inch industry standard ‘1U’ footprint (50.8 x 101.6 x 32.3 mm) the series has a convection cooled output power rating of 150 Watts which is believed to be “best in the industry” for a power supply of this footprint. Output power of up to 225 Watts is available with only 10 CFM of forced airflow.

The EPL225 series offers a minimum average efficiency of 93% and a maximum efficiency of 95% resulting in less heat to dissipate and a cooler running unit, the later contributing to a more reliable longer-life power supply. In addition, the units “green” attributes include a no-load power consumption of less than 0.5 Watt enabling compliance with the latest environmental goals and legislation.

The series complies with the universal safety standard EN 60950-1 for IT equipment in addition to the medical safety standards ANSI/AAME/ 60601-1 and IEC/EN60601-1 3rd edition. With low conducted and radiated noise the units meet the standards EN55011 & EN55022 for Class B conducted and Class A radiated EMI specifications.

The EPL225 suits use in a broad range of operating environments with an extended temperature range from -20 to + 70 degrees C and no derating until +50 degrees C.

The EPL225 range offers a high power density solution and is ideal for space constrained applications that are either convection cooled or have airflow.

The EPL225 series is available, and come’s with a 3 year warranty.



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Innovative, Inline and Amtex Sales Conference FEB 2015



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EEA Conference 2015




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Inline Components Joins The Innovative Energies Group

Inline Components Joins The Innovative Energies Group

We are pleased to announce:


As of the 1st February 2015, Inline Components Ltd becomes part of the Innovative Energies Group of companies. This exciting development brings together the two main DC Power Solutions companies in New Zealand. The combination of the Cordex range of convection cooled industrial DC units from Inline with the Innovative Energies range of locally designed and manufactured DC power solutions and world leading imported products, provides industrial customers with an unbeatable range. More importantly, the combined experience and technical capability of the people in the business means customers have direct access to a wealth of knowledge on DC power, unmatched in New Zealand…..  read more…..


 Inline-Cordex Announcement



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Greg Russell                                                                                      Barry Johnson

INNOVATIVE GROUP                                                                   INLINE COMPONENTS

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Schaefer is ITAR Certified and Compliant

Schaefer is ITAR Certified and Compliant

17th September 2009               News Release from: Schaefer Electronic


Schaefer Inc. has announced that it is an ITAR Certified and Compliant company. ITAR (International Traffic in Arms Regulations) is a set of United States government regulations that control the import and export of defense-related articles and services on the United States Munitions List.

ITAR regulations implement the provisions of the ARMs Export Control Act and are interpreted and enforced by The U.S. Department of State. ITAR regulations dictate that information and material pertaining to defense and military related technologies may only be shared with U.S. Persons.

Schaefer designs and manufactures COTS and MOTS power converters that have been certified to MIL-STD-810, MIL-STD-461, MIL-STD-704D, MIL-STD-1399 and other critical standards. A product offering of 6000+ heavy industrial COTS power converters can be easily optimized to satisfy most user-defined electrical, mechanical, and environmental requirements. Designed for mission critical applications, Schaefer’s products offer such features are weatherproof/waterproof enclosures, increased mechanical strength, and extended temperature operating/storage conditions.

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What does ITAR Compliant/ITAR Compliance mean?

What does ITAR Compliant/ITAR Compliance mean?

The U.S. Government requires all manufacturers, exporters, and brokers of defense articles, defense services or related technical data to be ITAR compliant. If your company falls under these categories, the following information will help answer some of your questions.

More and more companies are requiring that members of their supply chain be ITAR CERTIFIED or ITAR COMPLIANT. Language to that end is often contained in contracts, on purchase orders and request for proposals. Nowhere in the International Traffic in Arms Regulations (ITAR) is it spelled out what “ITAR certified” means. If you speak to different staff members of the Directorate of Defense Trade Controls (DDTC), you may get slightly different answers, but the “not for attribution” acceptable, generally safe definition is as follows:

For a company involved in the manufacture, sale or distribution of goods or services covered under the United States Munitions List (USML), or a component supplier to goods covered under the USML, the stipulation or requirement of being “ITAR certified (compliant)” means that the company must be registered with the State Department’s DDTC, if required as spelled out on DDTC’s web site and the company must understand and abide by the ITAR as it applies to their USML linked goods or services. The company themselves is certifying that they operate in accordance with the ITAR when they accept being a supplier for the USML prime exporter.

In other simpler words, to be ITAR COMPLIANT, a company needs to register with DDTC and know what is required of them to be in compliance with the ITAR, and self certify that they possess this knowledge. This explanation does not constitute legal advice and is not for attribution. If in doubt as to how this concept applies to your company, you should seek legal advice.

The ITAR can be found at: ITAR Regulations

Article from Government Contracts Blog: New DOD Rule Imposes Contractual Requirement For Contractors To Comply With U.S. Export Laws

What is important to understand is that even though you may register your company with the DDTC to sell your products or services in the ITAR industry, you must also not violate ITAR compliance regulations. You are expected to be educated and trained in ITAR regulations. Violating the ITAR may result in criminal or civil penalties, debarred from future exports, as well as imprisonment.

The International Import-Export Institute at Dunlap-Stone University offers the TRD-306 Understanding the ITAR six-week online class. Many companies new to the ITAR industry choose this class for gaining a practical knowledge and to help protect their company (and employees) from violating ITAR regulations. For more information regarding the International Traffic in Arms Regulations, and our online ITAR classes, please do not hesitate to contact us. Learn more about trade compliance.

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