Power Supplies Peak Load For Power Supplies —How Much, For How Long?

Related Vendors

RECOM Power GmbH

FAULHABER Drive Systems

Wuxi InfiMotion Technology Co., Ltd.

Efficient power supplies designed for peak loads significantly contribute to the reduction of energy consumption and the increase of system reliability— especially during recurring or short-term peak loads.

When selecting a power supply, it is not sufficient to merely align the rated power with the maximum expected continuous load. Many applications exhibit variable load profiles—with typical load, maximum load, and transient peaks that exceed these. Power supplies are often able to cover such peak loads above the rated power for a limited time, which, however, requires precise design and monitoring.

Efficiency And Environmental Conditions

High efficiency is crucial to minimize losses and heat generation. Power supplies—both AC/DC and DC/DC—must operate reliably under varying environmental conditions such as ambient temperature, humidity, and voltage fluctuations. They must be able to provide their rated power immediately and maintain this consistently within their design. Continuous monitoring is necessary to prevent overheating and ensure reliability. Since many electrical consumers do not have a constant power consumption, load fluctuations frequently occur. This includes inrush currents, counter-EMF from motors, or surge loads at startup. Especially in HVAC systems, such factors significantly affect the base load, highlighting the need for more efficient systems and upgrades.

Temporary overload capability

Power supplies can be operated above the nominal output for a short time. To prevent damage, many manufacturers specify not only the continuous load but also an allowable peak load. Two critical parameters in this are:

• the maximum duration of the peak load,

• the necessary cooling time between peaks.

During development, engineers plan for a so-called headroom—a temporary overcapacity to cover such peaks. This headroom allows for a short-term overload without affecting the lifespan. Particularly with time-dependent electricity tariffs and load management systems, behavior during peak loads is also relevant from a cost perspective.

Example: Recom Racpro1-T480 Series

A practical example is the DIN rail power supply of the Recom Racpro1-T480 series. This device can deliver a peak power of 250% for up to 20 ms. A moderate overload of 150% of the rated power is permissible for up to 7.5 s. After a full peak load, the load must be reduced to 100% or less for 52.5 s. Peak loads may occur only every 60s. This results in utilization rates of 0.03% at 250% load and 12.5% at 150%.

This information shows how precisely power supplies need to be designed and operated to work reliably even under non-constant conditions. With appropriate peak load capability, smaller and more cost-effective devices can be used without compromising function or lifespan.

Management of Multiple Peak Loads

Some applications regularly generate multiple peak loads—for example, conveyor motors, which mostly run evenly but occasionally have significant load changes. In such cases, energy storage solutions like batteries gain importance: they balance peak loads by absorbing energy during low network load and releasing it when needed.

Vehicle-to-Grid technology (V2G) also becomes relevant in this context. It allows electric vehicles to act as decentralized energy storage units and feed energy back into the grid when needed. This helps reduce peak loads and increase grid stability.

Another important aspect is the average required power, which is usually significantly below the short-term peak load. This insight allows for more efficient design: instead of designing a power supply for maximum demand, a smaller device can be chosen that is temporarily overloaded during peak times—provided that conditions (e.g., cooling times) are observed.

Summary

The rated load describes the maximum continuous power of a power supply under defined environmental conditions. The peak load, on the other hand, is the maximum permissible short-term overload without causing permanent damage. This can be two to three times the rated power, but must be limited in duration and frequency. Proper handling and design of peak loads are crucial to operate a power supply efficiently and reliably.

Peak loads often arise from motor starting currents, inrush current, or sudden load changes. Therefore, system developers must consider peak load magnitude, duration, and interval in addition to continuous load when selecting components. This requires careful analysis of the data sheets for both the power supply and the load.

Efficient power supplies designed for peak loads significantly contribute to reducing energy consumption and increasing system reliability—especially in applications with recurring or short-term peak loads. (aru)

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