Power derating in practice
Protecting your power supplies from overheating and premature failure
Power Supplies I 27.06.2024
Increasing efficiency is leading to smaller and smaller industrial power supplies and a consistent increase in power density. But what application-dependent factors need to be taken into account with regard to the actual possible power consumption? Often, in practice, insufficient attention is paid to power derating.
Background
Most power supply makers provide information about the service life, output current, and reliability of their products, but this only applies to specific ambient conditions. To avoid overheating or early failure of the components in the power supply, power derating must be taken into account. Derating relates to a reduction in output power resulting from the ambient conditions and is thus a protective factor that ensures that a power supply unit works reliably under all operating conditions. Based on these operating conditions, the power reduction is precisely defined for each power supply. It is particularly important to take this into account in industrial power supplies – with increasing efficiencies, these are becoming smaller and smaller, and the power density is increasing accordingly. As a rule, derating is not automatically controlled by the power supply, but must be taken into consideration, case by case, during product development. This is the only way to ensure the long-term operation of a power supply unit under the given conditions. Users can find the specifications for the necessary power reduction in the corresponding data sheet, while the derating curves for adjusting output current based on the ambient conditions are also helpful. As well as derating due to higher ambient temperatures, possible derating due to the installation position, cooling design, input voltage range, and maximum operating altitude must also be considered during product design and installation.
Image 1: Derating curves as a function of ambient temperature, input voltage, operating conditions, and installation position for the LOP-600-24 power supply unit (Source: MEAN WELL)
Dealing with the derating of switching power supplies can be simplified by:
• Using power supplies with a higher rated power: This allows more latitude while staying within the operating limits, making derating less critical.
• Selecting power supplies with a wider operating temperature range: This allows for more stable performance under varying environmental conditions.
• Implementing more efficient cooling systems: Improved heat dissipation can stabilise the operating temperature of the power supply, making derating less restrictive.
• Adherence to manufacturer specifications and recommendations: Strict adherence to specifications and operating limits will help avoid potential derating issues.
Solution
As a leading producer of standard power supplies, MEAN WELL closely monitors the demand for compact power supplies with ever-higher performance. The new generations of open frame power supplies, MEAN WELLs LOP series,, have a high power density of 30.8W/inch³ and efficiency of up to 95%. Nominal output power ranges from 200 to 600W and the standard models offer a range of output voltages (12, 15, 18, 24, 27, 36, 48 and 54V).
The universal input range of the LOP series, from 80 to 264V AC – with no input-voltage-related derating above 115VAC – means they can be used worldwide. The power supplies in the series can be operated with both free-air convection and active cooling, with a 12V fan output pre-integrated for this purpose - a separate power supply is no longer required for the fan when operating with active cooling. When working with inductive or capacitive loads, the generous peak power capability allows 150% output power for up to 3 seconds to handle short-term peak loads.
With their wide range of certifications, the power supplies in the LOP series are suitable for industrial applications (IEC/EN/UL 62368-1), medical 2xMOPP applications (IEC/EN/ANSI/AAMI 60601) and household applications (IEC/EN 60335-1). In accordance with IEC/EN 61558-1/2-16, they are also suitable for applications in overvoltage category III (OVC III) for operation at altitudes up to 2000 metres.
At Schukat
Schukat electronic offers power supplies from a range of manufacturers, including MEAN WELL, RECOM POWER and Self Electronics. Schukat stocks around 6000 different types of power supplies and DC/DC converters in production quantities at its automated central warehouse in Monheim am Rhein, Germany.
As a distributor, they provide fast, competent support with direct contact persons, and also offer an expert field service team for on-site problem solving. Customers benefit from rapid processing of enquiries, availability of data sheets and samples, and variable delivery quantities, from samples to series production.