Case story: How AHF put a stop to packaging manufacturer’s production outages


One of Canada’s largest manufacturers of innovative and sustainable packaging products was facing multiple transformer failures and production stops due to power quality issues at one of its many sites. The manufacturer needed to find a way to eliminate these recurring problems and troublesome interruptions. Multiple studies on power quality were performed by different contractors. Comsys Partner, ADM Engineering, was one of the companies performing power studies and providing analysis report.


The challenge facing ADM was to determine what was causing the periodic failures in the main transformers and to recommend a reliable remedy. Following site measurements and subsequent analysis of the data captured by ADM and Comsys, the root of the problem was identified. The culprit was the resonance caused by the interaction between the natural resonant frequency of the power system, tuned capacitor banks, and nonlinear loads. Based on these findings, ADM was able to recommend ADF as the only viable solution to the site’s persisting problems.


ADF P300 – Active Harmonic Filters engineered and assembled by ADM using PPM300 modules.

ADF at site


The ADF solution has been operating successfully since January 2020, eliminating resonance and harmonics

The ADF solution has been operating successfully since January 2020, eliminating resonance and harmonics as well as providing near unity power factor. Cost savings alone have amounted to around CAD 30,000 per month by eliminating harmonics and correcting the power factor. Increased uptime and productivity provide even more value.

Key Results:

  • Mill power outage frequency significantly reduced
  • Oil cooled transformer runs much cooler and requires less frequent oil changes
  • Significantly reduced running temperature of several transformers
  • Reduced nuisance trips and blown fuses of 600V switchgear
  • Reduced saturation of feeding transformers, reduces voltage variations to nominal values

Current THD - before & after installing ADF

Current THD – before & after installing ADF

Power Factor - before & after installing ADF

Power Factor – before & after installing ADF


Machine drives system supply voltages before active filters installation

Machine drives system supply voltages before active filters installation

Machine drives system supply voltages after active filters installation

Machine drives system supply voltages after active filters installation

Resonance damping using Active Harmonic Filter

LOCATION: Munich, Germany


SWM Services GmbH München is the public utilities company that supplies the city of Munich with electricity, natural gas, district heating and cooling, as well as fresh drinking water from the Bavarian Alpine foothills.

At one of their geothermal plants used for power generation and district heating, the use of a large number of frequency converters was creating major problems that only a solution from Comsys could solve. Fortunately for SWM, our partner in Bavaria, PQ ENGINEERING, was there to help


At their Sauerlach geothermal plant in Munich, thirty six frequency converters on a single transformer are used for the cooling units. Due to the high capacitive components of the load, a resonance point is formed in the network at the 25th harmonic. The resonance is so extreme that it was causing not only unusual noises, but also massive violations of EN 61000-2-4 class 2 limits, along with warranty issues for the supplier of the electrical equipment.

references gtk without filter

Picture: Resonance without Active Dynamic Filter installed 


After acceptance measurements carried out by PQ ENGINEERING revealed the limit value violations, a test installation with the active resonance damper Comsys ADF P200-100 was carried out. PQ ENGINEERING keeps these universal filters in stock for quick response to just such “emergencies”. Targeted programming of the filter’s impedance enabled the increased harmonics in the area of the resonance point to be reduced to a permissible level. After the test installation was completed, ADF P200 filters were installed on both of the main distributors. No other supplier was able to offer an active controlled solution for resonance damping.

Voltage harmonics kept well within the limits at all times ADF P200 (first generation) installed


The solution completely dampened the resonance, thus eliminating the severe compliance issues. 

Ralf Nosswitz quote

references gtk filter

Picture: Resonance after Active Dynamic Filter was installed


• Highly dynamic damping of the resonance point
• Flexible use, even if the customer makes changes later
• Easy retrofitting in the fully assembled switchgear

Sneakpeek at Danfoss new Active Harmonic Filter

At the SPS fair in Nürnberg 2019, Danfoss gave a sneak peek its new active harmonic filter for high power quality applications. Sources say it is due to be launched in q1 of 2020. We look forward to check out its specifications. Danfoss was the first drives manufacturer to use active harmonic filters as a solution for their low harmonic drives, often applied when complying with for instance IEEE519.  Last year Schneider followed up showing its Active Harmonic Filter in combination with multiple drives at SPS, see Active Harmonic Filters & Drives. The Danfoss filter AAF007 seems to be modular based on the picture presented.


Danfoss new Active Harmonic Filter AAF007


Active Harmonic Filters & Drives

If you have followed this site you know that for large drive applications the combination of VFD + AHF have several advantages over the serial solution AFE.  By placing the Active Filter in parallel you obtain a more secure derive solution as well as higher efficiency. The losses in the Active Filter are about 25-30% of the losses in the Front End on a system-wide basis. The AFE has to pass the whole drive power through itself as it is placed in series with the load. The shunt mounted Active Filter however is sized based on the harmonic mitigation requirement, normally around 25-30% of total load.


Schneider showcasing the combination of Active Harmonic Filter & Drives for higher energyefficiency at the SPS2019 fair in Nuernberg.

For more on Active Filters and rives see the Global Active Filter Compensation post with an excellent paper on the advantages.






Small is the new black in the Active Harmonic Filter market

It is not only ABB and Schneider that release new, smaller Active Harmonic Filters. Comsys, a Swedish company specialized in Active Harmonic Filters presented their new ADF-P25 model at the SPS Nürnberg last November. We got a chat with Rickard Jacobson, Head of Sales and Marketing at Comsys.

“We see an increasing demand for smaller filters in applications such as datacenters and commercial buildings where harmonics is an increasing issue. We scaled down our current design to 30A but it offers all the functionality and robustness that you find in the larger industrialized versions. As this filters will be broadly utilizedused we have focused a lot on simplicity, plug and play, making it very easy to commission and operate. We offer the option of Sensorless control as well as WiFi to access a bigger user interface on a mobile device.

We think this can be a great entry offering as customers can test the solution without allocating too much funds. It fits well with larger HVAC systems and building technology in general.”


Small Active Harmonic Filters from Schneider

Schneider dedicated 3 meters of exhibition space to its active harmonic filters at the SPS fair in Nuernberg this year. Great to see that the big boys are catching on. Schneider is no newcomer to the field though, rather one of the biggest suppliers of active filters world wide. This is the first year they show these products at the SPS.  This year small filters down to 20 A is a new offering from Schneider in the PCSn series. We assume this will broaden the application scope significantly.


Source: Schneider

For more info check out the PCSn flyer Schneider_PCSn_998-20306747_GMA

ABB launches new Active Filter

Active Harmonic Filters are moving into the mainstream. As the world embrace renewables, electrical vehicles etc the amount of inverters in the grid is growing. As the share of inverters grow, the stability of the entire power grid will be more vulnerable as the amount of turbine inertia is reduced. The last decade is already indicating a dramatic change in grid behaviour through the 24 hour cycle. Active grid stabilisation will become a need.  Several suppliers of Active filters are adopting battery integration to provide a complete solution to offer active, reactive and harmonic mitigation in one box. Now ABB is launching a new series of products.


The new portfolio comprises five solutions: PQflexC – variable reactive power controller; PQdynaC – ultra-fast reactive power and unbalance controller; PQactiF – active harmonic filter; and PQStorI – battery storage inverter with power quality functions. Finally, PQoptiM controls and monitors power quality parameters. The product family is further enabled by ABB Ability™ to allow the devices to be operated and controlled via cloud-connected user platforms to enable real-time access of data. See more here.

We look forward to see more of the specs as they become available. Great to see ABB expanding their offering in this segment.

Global Active Filter Compensation

Comsys has released a application note explaining the detailed advantages of using central filtering of many drives rather than installing separate low harmonic drives. A central active harmonic filter is often the cheapest and most efficient answer to maintain code compliance.

Read the report here: Global-vs-Local-Compensation_Application_Note

Schaffner updates its modular active harmonic filters – Ecosine Active Sync

Schaffner launches an updated version of its rack mounted active harmonic filter with higher efficiency and heat tolerance as we understand.

ecosine ahf freigestellt

Schaffner reports:

The modular design of ecosine active sync always allows a suitable filter size to be supplied and, in addition, the 60 A modules can be easily fixed to the wall or integrated into system control cabinets. Simply slide in and wire up – a filter from up to 300 A per cabinet is ready.

ecosine active sync in detail

  • Most effective harmonic mitigation up to 50th order (odd and even). Below 5% THID achievable even for mixed and dynamic load profile.
  • Most compact and modular design. Flexible and easy installation.
  • Robust, reliable and suits the broadest temperature (power module up to 50°C) range with full performance.
  • High efficiency (< 2.3% losses) and very low acoustic noise.
  • Only air cooling for all product variants with IP 20 power module, IP 21 (roof kit) and IP 54 cabinet version.
  • Reactive Power Compensation
  • Load balancing
  • Modular ready to use, retrofit integration in slide-technology cabinet
  • Ultra-flexible mounting and installation options


Active Filter on offshore MPSV- case study

Bourbon Offshore MPSV

Comsys has supplied Active Harmonic Filters to multiple offshore supply vessels. Bourbon Offshore, one of the biggest operators of offshore service vessels is using active filtering on their Evolution series of MPSVs. Filtering is employed on the main busbar to comply with class regulations. For a full report on the project and the result see here:

Bourbon Offshore Case by Comsys