Addressing Power Quality and EMC Together

­When designers are working on developing new electronic products or components, they often struggle to consider the issue of electromagnetic compatibility (EMC) and what that means in terms of electromagnetic interference (EMI). The best way of tackling this problem is, of course, to incorporate filters into the original design process and Schaffner works with designers around the world to help them understand why filters are important.

However, what is often not fully appreciated is the role that power quality plays in this process, in particular how important the relationship is between power quality and EMC. It is imperative that designers who are aware enough to focus on EMC / EMI issues when working on products also consider power quality. If all three factors are not addressed correctly, and at the same time, damage to products or to devices that they interact with will almost certainly be the result.

Why Is Power Quality Important?

We are living in an increasingly electrified world. The continuity of power, quality of power and availability of power are important today but will become essential in the future. That is why engineers need to understand how to maximise all of these and to know what solutions are available.

Put simply, if you want to have reliable and efficient usage of energy then you have to embrace the concept of EMC and combine this with delivering good quality power. It is essential for our modern life that power quality is given top priority. If not, the electronic devices that we have all come to rely on will simply not work to the levels of reliability and efficiency that we need.

Looking at the bigger picture, energy will be wasted, the efficiency of power networks and power lines will be compromised, equipment downtime will increase, and damage will occur. Also, from a financial point of view, it has been estimated that power quality problems cost businesses and organisations in the EU around EUR 10bn a year. This clearly provides a powerful incentive for engineers everywhere to tackle the issue.

When trying to appreciate the relationship between EMC and power quality, it is important to understand that the differences between them relate to power frequencies. In Europe, power frequencies usually start at 50 Hz and go up to several MHz, depending on the application. In terms of power quality, the important range to focus on is between 50 Hz and around 2.5 KHz and this is covered by the European power quality standard EN 50160. EMC / EMI usually become an issue at the 2.5 KHz level.

Harmonics Distortion

When power quality is not as high as it should be, that is mainly down to the issue of harmonics distortion (HD) of the electricity supply system. HD is what happens when a signal's waveform is altered, introducing unwanted harmonics. It can disrupt electrical systems, causing overheating, equipment damage and inefficiencies in energy transmission and consumption. The more distorted power is, the less efficient and reliable energy becomes. In many countries, maximum HD levels are dictated by law.

In industry, a significant number of issues and malfunctions are caused by poor power quality. Devices can get hotter than they should and need replacing earlier, incurring avoidable costs. If a motor drive in a manufacturing facility fails, for example, this can bring the entire production process to a halt. Even if failure does not occur, poor power quality can cause machines to run less efficiently and become less reliable, causing delays, disruption and more unwanted expense. By tackling harmonics distortion and eliminating losses, factory owners can keep their facilities operating at peak efficiency while minimising costs.

In the 21st century, motor drives are by far the most used devices in electronics and energy-saving variable speed drives have come to be used extensively in factories. Indeed, as much as 50% of all energy consumption today relates to motors. The downside of this is that the proliferation of motors inevitably increases the level of harmonics distortion that is present in power networks. While individual variable speed drives can be checked against standards in a laboratory, the challenge is what happens when 100 or more of them have to operate together in a large production facility.

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Figure 2: Electrical motors increase the level of harmonics distortion that is present in power networks

Power Quality ‘Black Magic’.

Unfortunately, many engineers today still see the relationship between power quality and EMC as some sort of ‘black magic’ that is difficult to fathom. However, there is no mystery to the fact that engineers should always be looking to mitigate the risk of disruptions, improve efficiency and enhance the overall quality of electrical power and electromagnetic environments. To do this, they need to address such vitally important factors as voltage stability, waveform distortion, electromagnetic compatibility and immunity to interference.

It is simply not possible to neglect the issue of power quality, whether designing a product or setting up a factory. EMC and power quality must always be tackled together in the drive to minimise losses. While engineers need to look at the bigger picture rather than just focusing on tackling EMI or improving power quality, there are very few solutions providers globally that can help them to deal with the whole spectrum.

Power Quality and EMC Solutions

For many years, Schaffner has specialised in solutions that tackle power quality and EMC issues together. They include input and output filters, passive and active harmonic filters, reactors and power quality simulators.

Input filters ensure stable and clean power delivery by dealing with harmonics and reactive power, reducing EMI, smoothing power supply voltages and filtering out unwanted noise. An output filter removes noise and ripple from a signal, ensuring smooth and stable voltage output, enhancing performance and reliability. Schaffner’s output filters not only reduce power losses but also enable customers to use longer power cables, which can be crucial in such applications as mining.

Passive harmonic filters attenuate specific frequencies, while active filters actively cancel out harmonics, improving power quality and reducing distortion. Reactors, typically used in combination with other filters as part of a whole solution, enhance power quality and protect equipment from damage by controlling current flow, reducing HD and stabilising voltage levels.

One area where Schaffner is unique is in its development of power quality simulators. There are many applications where simulation is the only viable option, for example if a factory has not yet been built but calculations still need to be made on equipment so that investments and budgets can be agreed. Now engineers have a tool that enables them to calculate the number of filters that will be required. They input into the power quality simulator such factors as the number of drives, the power source(s), loads and lengths of cable and the simulator works out the distortion level and proposes the optimal filter solution, including how many filters will be needed and where. Once equipment has been installed, the simulator can be used to check if its calculations match the reality. This very powerful tool is akin to engineering artificial intelligence.

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Figure 3: Power quality simulators help calculate the number of filters that will be required

Conclusion

To summarise, having good power quality and electronic devices that are electromagnetically compatible are essential factors in the modern world. If we want to have reliable and efficient usage of energy, then we need to be achieving maximum levels of EMC and power quality. Unfortunately, in the real world the situation is not as good as it should be. There are still too many issues associated with high levels of distortion and it is essential to the way we live our lives today that these are dealt with. If they are not, we cannot expect our modern devices to work reliably and efficiently, and the quality of our lives will be diminished.

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