What is a DIN Rail power supply?
This central unit for the power distribution takes the AC line voltage and converts it to DC voltage and is located in a electrical cabinet mounted on a DIN rail. This metal strip has standard dimensions originally defined in the specifications published by “Deutsches Institut für Normung” (DIN) in Germany, which have since been adopted as European (EN) and international (IEC) standards.
As DIN Rail is a globally accepted standard, the user has a wide range of components at his disposal. System components such as relays, contactors, multipliers, circuit breakers, power supplies can be mounted conveniently on the practical 35mm rail. This means that even complex systems can be implemented quickly and safely.
DIN-Rail power supplies are typically used in control panels and electrical cabinets to provide industry standard 12V, 24V, or 48VDC. Applications include: motors, valves, solenoids, or nonlinear loads where the startup currents can be very high. Typically they need to be certified to UL standard 508 safety and performance standard for factory automation and the UL60950 general purpose power supply standard.
Not surprisingly, due to the fact that prices for DIN rail modules have become so low because of "economy of scale" and intense competition, they are becoming increasingly attractive for smart home applications, security technology and building automation.
What to consider when selecting a DIN Rail power supply?
When you are looking for the right DIN Rail PSU for your cabinet, there are a couple of key points to consider, which will help you find your way in the vast variety of AC/DC DIN Rail power supplies on the market.
Input / Output
To guarantee worldwide compatibility, it is advised to look for wide AC input voltage ranges, which cover most line voltages, and also accept wide frequency ranges.
Adjustable outputs are designed for specific needs in test and development applications, however the typical output voltages are a stable 12V, 24V, or 48VDC industry standards. 24VDC seems to have established itself as the standard supply voltage in the entire automation technology - from mechanical engineering to telecommunications to the oil and gas industry.
Relays, solenoids and control valves work with 24VDC as well as hydraulic or pneumatic drives. The same applies to a variety of sensors for pressure, temperature, flow or level and also for most gateways, programmable controllers and bus systems. A market analysis based on around 100,000 sold DIN rail power supplies assumes that modules with 24VDC output are sold more than four times as often as all other modules summarized - followed by 12VDC applications.
Operating temperature range
A major benefit of a DIN rail system is how space-saving they can be aligned, which allows to fit the entire cabinet in locations with extreme temperatures. Integrating cooling fans in these sealed enclosures can almost never be realized, so the power supplies have to be designed to function in extreme temperature environments without them. This is why a DIN rail PSU typically can operate over a wide temperature range. When reducing the output power (derating), most PSUs can be operated at higher temperatures according to their derating graph.
The DIN rail PSU can be subject to electrical errors originating from mains or the connected load. This is why they need various safety features in the case of an error. Protections against short circuit, over voltage, over temperature and over load are essential for a reliable operation. Some DIN rail PSUs feature hiccup protection, where the unit resumes operation automatically post-error, others need to be restarted manually.
Efficiency and no-load power consumption
In a closed cabinet without forced cooling, any additional dissipated heat can result in a temperature where some components quit working reliably. It is therefore advised that the central DIN rail power supply features a high efficiency of a minimum of 89%, which keeps the dissipated heat to a minimum. A low no load power consumption can also assist to reduce additional heat dissipation.
UL 508 Industrial Control Equipment Standard
DIN rail PSUs sold for the US market must comply with the Underwriters’ Laboratory National/International Standard UL 508, which regulates the use of all industrial control equipment, such as power supplies, selector switches, relays, contactors, motor starters and devices which include such components. This standard includes devices up to 1500 V and intended for use in an ambient temperature of typically 0 – 40°C.
Connection and wiring
Generally speaking, all wires connected to the PSU should be designed in the largest cross section and shortest cable length possible. This is to minimize cable losses on the loadside, to prevent adding heat to the cabinet. From the mains side this minimizes the effects of occuring noise.
Parallel Operation & Phase Redundancy
For power-hungry applications and redundancy purposes, some DIN rail units can be connected in parallel with no need for additional components. For connecting in parallel, they feature a switch for “Parallel Use” and then each needs to be power derated by a factor < 1.
Reliability & Low Maintenance Cost
In professional applications where you can not afford to have a failure, it is recommended to not focus on the price exclusively - especially quality and life expectancy should be firmly in your view. If production is at a downtime because a cheap capacitor has failed, a few dollars saved on the power supply come in expensive.
The less effort required to maintain and repair a plant, the cheaper the cost of ownership. And that plays a far greater role than the cost of higher-value components, for example, reflected in the purchase price of a power supply. That is because power supplies are undoubtedly one of the critical components of a system. If a voltage fails, parts of the system stand still. The cost of a production outage can quickly add up to more than 100 times the hardware. Therefore, it pays off for professional applications to rely on particularly secure technology.
With the experience of many millions of DC/DC and AC/DC converters produced, we have developed a series of DIN rail power supplies designed for maximum operational life. In order to create corresponding safety buffers, without exception only the highest quality components were used, whose operating temperature is well above the values specified for power supply units.
Our high-quality AC/DC DIN-rail power supply series are available for either 1-phase or 2 and 3-phase mains environments. All PSU series feature high electrical strength and high reliability; ideal for industrial cabinets operating in harsh environments.
Unlike many other DIN-RAIL power supplies on the market, we offer a full five year warranty with a design lifetime of up to 22 years. They have been designed to be reliable under harsh industrial conditions where regular maintenance is not possible. Once installed, they simply just work without further thoughts - fit and forget.