Power supply

A modular DC power supply is a static converter mounted on a 35 mm DIN rail that converts the mains voltage into stabilised DC voltage. These switched-mode or linear power supplies deliver standard output voltages of 12V, 24V or 48V DC with power ratings ranging from a few watts to several hundred watts. They comply with IEC 61558 or IEC 60950/62368, depending on their technology, and provide local power to measurement, control and communication equipment installed in the same electrical panel.

Voltage and power ranges of modular DC power supplies

Voltage ranges and common ratings of DIN-rail power supplies

Modular DC power supplies cover three standardised output voltages: 12V DC for compact automation devices and relays, 24V DC for industrial sensors and PLC inputs/outputs, and 48V DC for communication systems and certain measurement modules. Our standard practice favours 24V DC as the standard voltage in industrial electrical panels because of its universal compatibility with automation equipment.

Range of available power ratings according to load requirements

Available power ratings range from a few tens of watts, for powering a single measurement module, up to several hundred watts for the centralised power supply of a set of automation devices. In the field, we find that precise power sizing avoids overheating and optimises the service life of filtering capacitors.

Mechanical integration and electrical panel compatibility

35 mm DIN-rail mounting and compact formats of switched-mode power supplies

Mounting on a 35 mm DIN rail is the universal installation method for modular DC power supplies in electrical panels. This system allows direct integration close to the modules being powered, whether relays, sensors or measurement modules such as the DIRIS and ISOM Digiware ranges. Feedback from installers confirms that this proximity significantly reduces electromagnetic disturbance linked to remote wiring.

Housing materials and heat dissipation of modular power supplies

Housings are made of metal or polyamide depending on the range, with designs optimised for natural or forced heat dissipation. The choice of material directly affects the switched-mode power supply's ability to maintain its performance at high ambient temperatures.

Typical applications and associated equipment in electrical panels

Power supply for electrical measurement and control modules

Modular DC power supplies provide the stabilised power needed by network analysers, energy meters and modular measurement modules installed in the electrical panel. Our installation experience confirms that a dedicated power supply located close to this measurement equipment improves acquisition accuracy and communication stability.

Power supply for automation and industrial communication systems

Programmable logic controllers, fieldbus couplers and industrial communication equipment require a regulated DC voltage with no load variation. DIN-rail switched-mode power supplies meet this requirement with response times to load variations of under a few milliseconds.

Regulatory compliance and marking of modular power supplies

Applicable IEC standards depending on conversion technology

Modular DC power supplies comply with the IEC 61558 standard for safety transformers and associated switched-mode power supplies, or with IEC 60950 and IEC 62368 for information- and communication-technology equipment. CE marking confirms compliance with the applicable European directives. We find that design offices systematically require this regulatory traceability in tender documents.

Distinction between linear and switched-mode power supplies

Switched-mode power supplies offer better efficiency and lower weight compared with linear power supplies, but generate more conducted disturbance, requiring input filtering. Our installation feedback shows that the choice between these two technologies is mainly based on the trade-off between efficiency and electromagnetic simplicity.

Frequently asked questions

Which output voltage should be chosen for a modular DC power supply in an electrical panel?

The choice depends on the equipment to be powered: 24V DC is the most common voltage for industrial automation devices and sensors, while 48V DC is often required for communication systems and certain DIRIS-range measurement modules.

Why should DIN-rail mounting be preferred for modular power supplies?

35 mm DIN-rail mounting allows direct installation close to the equipment powered inside the electrical panel. This configuration minimises the length of distribution cables, reduces voltage drops and limits sensitivity to electromagnetic disturbance.

Which standard applies to switched-mode power supplies for industrial applications?

Switched-mode power supplies for industrial electrical panels mainly fall under the IEC 61558 standard for transformers, power supplies and related equipment, or under IEC 60950/62368 depending on their technological field of application.

How should the power rating of a modular DC power supply be sized?

Power should be calculated by adding up the rated consumption of all connected equipment, then applying a safety factor of 20 to 30%. Our commissioning tests show that an insufficient power margin causes premature heating and degradation of the output capacitors.