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ACTIVE HARMONIC FILTERS

Posted by Lionel Bey

Bell is on the same wavelength with Schaffner

The food industry always strives for more efficient and powerful machinery. PQ Bell Food Group contributes to guarantee the highest quality in meat production as well as in meat processing. The Bell factory in Cheseaux-sur-Lausanne is part of the Bell Swiss division and specialized in processing of raw meat to deli products. In order to fabricate healthy and high quality deli meats, the products undergo several production steps like, e.g. cold and hot generation.

ECOsine_100A_freigestelltAt Work

Due to a technical defect after the opening of the plant in Cheseaux, a short-circuit caused an unplanned shutdown of the production. Schaffner active filters shall ensure from now on an unhindered production.

The ChallengeBell_Firma

Concerning the production, two main steps are under focus: the glycol loop for the plant cooling, involving two screw compressors with a power of 160 kW each and the heat pump which is using two piston compressors with a power of 80 kW each. Both the hot and cold generation compressors are being driven by frequency converters, which can, depending on the process realization, lead to harmonic frequencies.

After the opening of the plant in 2017, a short-circuit in the main low-voltage switchboard caused an unplanned shutdown of the production. It turned out that one of the screws in the main transformer cabinet became loose and fell on the live copper busbars, what led to the short-circuit. In order to avoid further disruptions, additional analysis were carried out which identified vibrations in the transformer cabinet structure, caused by excessive voltage distortion. The harmonic distortion was recognized as an aggravating factor to the vibration and as the reason for the loosening of the screw.

Harmonic frequenciesBell_Firma_02

Harmonics are a voltage or current, produced by the action of non-linear loads such as variable-frequency drives or converters. Adapters of television sets, computers or halogen lamps can also cause harmonic frequencies. The non-sinusoidal currents can cause a voltage drop, which leads to harmonic distortion.

Results

Active harmonic filters of the Schaffner’s ecosine active series have been installed to solve the identified problems with harmonic distortion and to ensure a reliable deli food production. Harmonic measurements were carried out to verify the performance of the installed active harmonic filters. Figures 1 and 2 summarize the measurement results and compare the voltage and current harmonics with and without Schaffner’s ecosine  active harmonic filters.

Diagramm_1_white-background

Figure 1: The voltage and current harmonics with and without Schaffner’s ecosine active harmonic filters

On the same wavelength

The implementation of the harmonic mitigation solution of Schaffner has effectively reduced the vibrations in the main distribution transformer’s cabinet, contributing to the safe and reliable meat procession and deli production.

Diagramm_2_white_background

Figure 2: The voltage and current harmonics with and without Schaffner’s ecosine active harmonic filters

The frequency analysis of the vibrations development at the low-voltage main distribution transformer shows mainly two frequencies, namely 100 and 200 Hz. These are two mechanical vibrations caused by the 50 Hz network itself. The two frequencies are harmonics from the main network due to the active power required from the refrigeration systems. All oscillations in the low-voltage main distribution caused by harmonic distortion are no longer present thanks to the compensation provided by the installed active harmonic filters.

 

Schaffner ecosine active filter

Schaffner ecosine active filters are comparable with sea waves: two waves of the same phase, amplitude and intensity meeting together neutralize each other. The electricity grid works on the same principle. The active harmonic filters analyze the distortions and react immediately with creating an opposing current in less than half a second. The collaboration between the involved partners led to a successful cooperation in sizing, installing and commissioning of the Schaffner’s harmonic mitigation solution. Figures 3 and 4 give an overview of the vibration measured at the main low voltage 1400 kVA transformer, before and after the installation of the Schaffner ecosine active harmonic filters. With improving the grid quality in real-time, the newly installed filters (ecosine active FN 3420/FN 3420/FN 3430) ensure from now on that the production of the Bell factory in Cheseaux-sur-Lausanne is carried out smoothl.

Diagramm_3_white_backgroundFigure 3: Vibration at the main transformer before (red) and after (green)  the installation of the Schaffner ecosine active filters.

Figure 4: Vibration spectrums with 100 and 200 Hz components, before (red) and after (green) the installation of the Schaffner ecosine active filters.

Figure 4: Vibration spectrums with 100 and 200 Hz components, before  (red) and after (green) the installation of the Schaffner ecosine active filters.

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