Slim DIN Rail Mounted Power Supplies

Sep 6, 2024
DIN-rail mounted RECOM REDIIN120-24, REDIIN240-24, REDIIN480-24 power supplies
DIN rail mounting has revolutionized electrical cabinets since the idea was first introduced in the 1920’s to standardize switchgear mounting and allow interchangeability between manufacturers. DIN stands for “Deutsche Industrie Norm” or the “German Industrial Standard” and the success of the DIN rail system rapidly spread outside of Germany, eventually becoming the European standard DIN EN 60715.

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The simplicity and versatility of the DIN rail system, where components can easily click into place or be unclipped for maintenance upgrades or replacement led to a whole range of different electrical components being manufactured for DIN rail mounting, such as circuit breakers, relays, contactors, terminal blocks, data network components (KNX, DALI, Ethernet), programmable logic controllers (PLCs), and power supplies (Figure 1).

Industrial electrical control panel with wiring and devices

Fig. 1: Typical DIN rail installation

The reason for the DIN rail system’s success lies in the following advantages

Firstly, the modular approach allows electrical cabinets and panels to be quickly assembled, moved, or rearranged for optimum use of the available space with only a standard electrician’s screwdriver as a tool. There is no drilling, cutting, or threading needed. Electrical cabinets and panels are often available with pre-installed rails so installation can begin immediately.
Thirdly, as the mounting rail dimensions are all standardized, parts from different manufacturers are interchangeable and mounting compatible. On a single rail, different electrical components can be freely mixed, so, for example, connector blocks can be placed next to power supplies to simplify the distribution of power and reduce the amount of cabling required, or actuator relays placed next to PLCs.
Secondly, the DIN rail system allows easy upgrading or repair without disrupting other components – a defective part can be simply unclipped and replaced without affecting the other components. If the new part happens to be slightly larger than the older module, then the existing components can be shifted along the rail to make space.
Fourthly, as you might expect from a German standard, the ease of mounting allows an organized, neat, and logical layout within the cabinet. This not only speeds up assembly by streamlining the whole construction process but simplifies maintenance and troubleshooting. All electrical contacts are accessible from the front without disconnecting any wiring and many electrical components have status or alarm indicators so that complex installations can be quickly inspected to find the fault.
RECOM's REDIIN120, REDIIN240, and REDIIN480
Fig. 2: REDIIN120, REDIIN240, and REDIIN480 DIN rail Power Supplies
In some ways, the DIN rail system has become a victim of its own success. As the DIN rail mounting system is now ubiquitous for almost all electrical, networking and telecommunication equipment, there is a tendency to try and cram as much as possible onto each rail. Each component should be as thin as possible to minimize the amount of rail space required. However, some electrical equipment generates heat, for example power supplies, contactor coils or relays, so placing these units in very close proximity to each other can adversely affect the natural convection cooling air flow. As every 10°C increase in ambient temperature halves the operational lifetime, this needs to be avoided if possible.

Solutions include adding spacers between equipment to allow free air convection to cool the components, to repositioning heat-generating components so that they are not in close proximity where they could warm each other up, or, in extreme cases, adding fans to force air cool the parts. The vertical separation between rails also needs to be considered so that warm air rising from one component does not adversely affect the component placed immediately above it. Fortunately, software packages are readily available that can be used to both plan the layout of the panel or cabinet in advance and to calculate the expected thermal loading. This software is often offered free by the cabinet manufacturers. More advanced software can also automatically check if the electrical safety, construction, and technical standards, such as EN 61439, are also being complied with.

RECOM is an established power supply manufacturer that is well-known for board-mounting or chassis-mounting embedded power, but also offers competitively priced AC/DC DIN rail mount power supplies (Figure 2).

Power supplies designed for DIN rail mounting need to have certain special features which makes them different from standard industrial power supplies

Always-on

Power supplies in panels and electrical cabinets typically operate in “always on” mode. Even if a production line is shut down overnight, the low voltage power supply for the relays and controllers stays on. Operating 24/7 means that DIN rail power supplies need to have a very long operational lifetime, which is assured both by careful design and also by heavy duty input filtering stages that can withstand severe input voltage fluctuations, supply interruptions, mains transients, and power surges.
Graph comparing efficiency vs. load for 115VAC and 230VAC
Fig. 3: Flat efficiency curve of the REDIIN120-24. No load power consumption is only 150mW

High efficiency

Both when fully loaded and un-loaded, high efficiency is needed to minimize the internal heat dissipation and to save energy during standby. The REDIIN series feature a flat efficiency curve which remains at around 90-94% for all loads from 20% or less up to 100% full load (Figure 2) independently from supply voltage. Under no-load conditions, the 480W version consumes less than 750mW, while the 120W and 240W versions both consume less than 300mW.

Design

DIN rail mounted power supplies are designed so that all the electrical connections are at the front and the major heat dissipating components such as switching transistors and power diodes are in good thermal contact with the back of the device (the so-called “book shape”). By using such a thermally efficient layout so that the metal DIN rail can act as an additional heatsink, the REDIIN series can operate at full output power at up to +50°C ambient temperature with only natural convection cooling. Sometimes, the environment may be very cold rather than hot, for example, in an outdoor solar farm PV string controller application or in an unheated warehouse, so low temperature operation is also important. The REDIIN series can operate at full load down to -30°C, with a cold start capability down to -40°C.

Protection

All REDIIN power supplies operate from a universal single-phase AC input (90 to 264 VAC), making them suitable for all global mains power supplies including undervoltage and overvoltage variations. Power factor correction is included as standard. The short-circuit, over-voltage and overload protected outputs are the typical industrial supply voltages of 12V (REDIIN 120), 24V or 48V DC, all trimmable over the range of ±10% to adjust for cable losses. They also have automatic CV/CC operational modes, making them suitable for either highly inductive or highly capacitive loads. An output over-current limit of up to 150% allows high start-up current loads to be driven without needing to over dimension the power supply. If the power supply is continuously overloaded, the built-in over temperature protection will safely turn off the output before the unit becomes damaged. A two-color indicator LED shows if the output voltage is within range or if it is in short-circuit, over-temperature or overload protection mode.

Summary

The cost-sensitive REDIIN power supply series are designed to fulfill the demanding technical requirements needed for many industrial-grade electrical cabinet applications without compromising on quality and reliability. The series are all housed in an extremely slim ‘book-shape’ case of only 123,6mm high and 116,8mm deep. The REDIIN120 delivers 120W output power with only 30mm width, the REDIIN240 delivers 240W with only 40mm width, while the REDIIN480 delivers an impressive 480W with only 56mm width. The exceptionally slim design frees up valuable space while the low weight avoids overloading the DIN rail in congested installations.

The products are fully certified according to international safety standards IEC/EN/UL 62368-1, IEC/EN/UL61010-1 and IEC/EN/UL/CSA61010-2-201. Electromagnetic radiated and conducted emissions are compliant with heavy industrial EN 61000-6-4 Class B Emission standard and EN 61000-6-2 Immunity standard.

The REDIIN series are intended for industrial, automation, power distribution and test and measurement environments and will find a wide range of applications in industry, heavy engineering, production, home automation, data and telecom, traffic control and water management - wherever and economical solid, reliable, DC power supply is needed inside of cabinets and other electronic enclosures.
Applications
  Series
1 AC/DC, 120 W, Single Output, DIN-Rail REDIIN120 Series
Focus
  • Universal input voltage range 90-264VAC
  • Built-In constant current circuit
  • Three output variations 12V, 24V and 48V available
  • Adjustable output voltage range ±10%
2 AC/DC, 240 W, Single Output, DIN-Rail REDIIN240 Series
Focus
  • Universal input voltage range 90-264VAC
  • Built-In constant current circuit
  • Two output variations 24V and 48V available
  • Adjustable output voltage range ±10%
3 AC/DC, 480 W, Single Output, DIN-Rail REDIIN480 Series
Focus
  • Universal input voltage range 90-264VAC
  • Built-In constant current circuit
  • Power Factor >0.96 115VAC & >0.93 230VAC
  • Two adjustable output variations 24-28V & 48-55V