Reducing Harmonic Distortion (HD) Without Regulations: Schaffner Filters Prevent Overheating in Fan Filter Units


The IEEE519 standard provides guidelines and recommendations for managing and controlling harmonic distortion (HD) in electronic power systems so that power quality remains high and electronic equipment is protected. Most countries enforce this standard or other international IEC standards, but in regions where there are no mandatory power quality requirements, such as Taiwan, the issue of harmonic distortion (HD) often becomes a low priority despite the potential impact on electronic systems.

Improving Power Quality and Efficiency

One of the key benefits of adhering to IEEE519 is the improvement in power quality, which reduces the likelihood of malfunctions and extends the working life of equipment. Other benefits include reduced downtime and maintenance, and improved efficiency. Occasionally, manufacturers of electronic devices can be lucky and don’t experience any problems relating to HD but one manufacturer in Taiwan found that its equipment, a fan filter unit (FFU), was failing regularly because it was overheating. FFUs are air filtering devices typically used in cleanrooms and controlled environments to provide clean air. The manufacturer wondered if the problem was due to harmonics and requested Schaffner to investigate the issue. Schaffner’s reputation in the industry for being experts in solving EMI challenges meant they were the obvious choice to go to for support. 

Simulating Power Quality Scenarios

Schaffner offered a full on-site power quality measurement service, carrying out measurements and simulations using its Power Quality Simulation (PQS) tool, which replicates various power quality scenarios to identify where HD is happening. A passive harmonic filter (PHF) from a local supplier had proved unable to meet performance requirements and Schaffner’s investigations found that overheating was occurring on the input and trap chokes, resulting in the failure. These chokes are essential components of a PHF, protecting electronic systems from the damaging effects of harmonics, so it is crucial for them to function optimally. Working closely with the FFU’s panel builder, main contractor and utilising its own expertise, Schaffner identified that the levels of total harmonic distortion (THD) in the equipment went significantly beyond those specified in the IEEE519 standard and recommend a solution from their own product portfolio. Schaffner selected a combination of its PHFs and active harmonic filters (AHFs) to ensure the system could operate within the standards, avoiding collateral issues. Designed into the cleanroom system at an early stage, the filters have been able to bring harmonics levels down to workable levels and prevent overheating in the chokes.
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