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effect on reliability than you might think.
The switch mode power supply (SMPS) has become increasingly efficient over the years, but when choosing one for an application, efficiency levels are sometimes overlooked in favour of reliability. Businesses can sometimes be willing to tolerate higher energy bills in exchange for buying the peace of mind that comes with the assumption that a power supply is less likely to fail or require frequent maintenance. But whilst reliability is clearly important, efficiency should not be overlooked, as it not only reduces energy bills, but can also have a positive effect on power supply reliability, as well as the reliability and performance of other devices around it.
Efficiency and reliability are inexorably linked. Low efficiency electronic devices generate more heat, and this can be compounded by the small space of the cabinet. The lifetime of electrolytic capacitors, for instance, is reduced by 50% for every 10°C temperature increase, so the lower the cabinet temperature, the longer they’re likely to last.
Heat dissipating from a power supply is in effect wasted energy, and can also have a detrimental effect on other devices. It can necessitate larger cooling systems, which will use up even more energy. The higher the efficiency of a power supply, the less heat it will generate. Less heat means that smaller cabinets can be used, or more can be fitted into them. Alternatively the freed up space can be left for natural convection, aiding cooling. For machine builders and OEMs this frees up vital capacity to uprate other components.
Cabinet air temperature can also be affected by nearby equipment, for instance motors, drives or inverters, all of which generate heat. This can be mitigated by performing a heat contribution summary of the enclosure components and a dissipation analysis to take account of where the cabinet is situated, be it outside, sealed, shaded or next to other heat sources.
There is no point having a power supply running if it is not needed. Power supplies, therefore, are now available that can be remotely controlled based on demand. When power is not required, the supply can be put into a low power standby state, thereby ensuring that the supply uses only the energy that it needs at any
Remote monitoring unlocks other areas of efficiency. Knowing what’s going on inside a power supply saves field inspection and simplifies troubleshooting, while providing enhanced data for asset management such as battery status, or letting operators know when components need replacing, freeing up maintenance teams for other tasks. This not only tells operators what’s happening inside the power supply, but can also provide feedback about the quality of the upstream power coming in.
The latest generation of SMPS products such as Wago’s Epsitron Pro offers up to 93% efficiency, and in addition to features such as the remotely controlled standby mode mentioned above, it also utilises advanced features such as Powerboost and TopBoost.
Powerboost is a function which provides additional current (up to 200% nominal rating) for four seconds to cope with heavy start-up current requirements. TopBoost provides a multiple of the nominal rated current of the power supply. For example, for a nominal current of 10A, the TopBoost feature guarantees 70A at 24V DC for 50ms, sufficient to trip the circuit breakers required by machine tools.
TopBoost is also available in some of the lower specification Wago power supplies such as the Epsitron Classic series. These features mean that power supplies can be sized for their normal operating loads, rather than being oversized to compensate for high inrush/start-up currents. This means that smaller, lower rated supplies can be used, saving space and reducing energy consumption.
Not every application requires these advanced functions, so at the other end of the scale, the new ECO series is aimed at the low cost, high volume market, and whilst it does not have the advanced features of the Pro series, it is very robust and compact. It offers a choice of installation options from DIN35 rail to screw mounting to fit into all types of enclosures and housings. It is also certified for EN 60335 conformity, allowing it to be used in household appliance applications.
The SMPS is fast becoming the power supply of choice compared to older linear models, and manufacturers continue to introduce new features and performance improvements to push efficiency and reliability further still, which in turn reduces both energy and maintenance costs.
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