Supplement: Power
Reliability in DC systems: application of buffer solutions
By Peter Huber, senior application engineer, PULS GmbH
(Source: AdobeStock) P
ower outages pose a significant risk to the operational continuity of electrical systems. In the United Kingdom, the average unavailability of electrical
energy, according to SAIDI (System Average Interruption Duration Index), is 18 minutes per end consumer per year (as of 2019). In comparison, the corresponding value in the USA is 125.7 minutes (as of 2022). The causes of these interruptions are diverse and range from weather-related impacts, such as ice loads and lightning strikes, to technical faults in the transmission and distribution levels, and even to deliberate interventions in the grid structure in the form of sabotage or cyberattacks.
24 July/August 2025
In industrial applications in particular, even brief voltage interruptions on the DC side can lead to significant disruptions: unplanned system shutdowns, data loss in programmable logic controllers (PLCs), timing errors in drive controllers, as well as thermal and mechanical stress caused by uncontrolled shutdowns of loads. To protect critical DC consumers, uninterruptible power supplies (DC UPS) and buffer modules are therefore used. This article focuses on the technical requirements, selection criteria, and application limits of capacitor-based buffer modules for short-term bridging in the millisecond range using practical application examples.
Components in Electronics
Bridging very short-term power interruptions and fluctuations Very short-term power interruptions and fluctuations in the millisecond range are often underestimated. Standard industrial power supplies already include an integrated hold-up capacitor, which can bridge such events for approximately 25 ms to 50 ms. If this is not sufficient, additional buffering time must be provided. Buffer modules with electrolytic capacitors are ideally suited for bridging short-term power interruptions of up to 200 ms under nominal load. They are easy to integrate, compact, completely maintenance-free, and designed for a wide temperature range. Their typical service lifetime exceeds 10 years.
The energy stored in the capacitor directly determines the bridging time during a power outage. Therefore, it is important to know the stored energy (E) in the capacitor (C). It can be calculated from the capacitor voltage (U) using the following formula:
For the design of a buffer module, this means: A greater stored energy can be achieved either by increasing the capacitance or the charging voltage. However, increasing the voltage has a quadratic effect! That is why PULS focuses
www.cieonline.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64
