Preventive Maintenance

Keep your line availability at maximum

Unstable power supply?

The last Newsletter no. 8 showed the importance of a stable power supply in the performance of film stretching lines. The consequence of variations in power supply can be unplanned production interruptions. These must be avoided, not only because of the accompanied production loss, but also in order to protect the sensitive equipment of the line.

Experiences from a film stretching line

In the following, we show the latest results of a power analysis from a BOPP line. The situation at the line was as follows: the power distribution has 2 transformers with 11 KV/415V, each 3000KVA, and 22 feedings to the stretching line. The records were taken from January until May 2014. During that time the line stopped seven times due to power interruptions!

The power analysis examines the following aspects (according to the European norm EN50160):

  • Frequency
  • Voltage deviations
  • Flickering altitude
  • Voltage unbalance
  • Total harmonic distortion (Voltage)
  • Harmonics (Voltage)

Additionally:

  • Sub-harmonics (Voltage)
  • Ripple control signal
  • Disruptions
  • Voltage dips
  • Voltage peaks
  • Transient/temporary overvoltage

Installation of the analyser

For safe and easy handling of the Brückner power analyser, the installation is possible in one of the feedings to the lines of the 415V distribution. There are two versions available:

  • Temporary installation: The analyser kit is a portable version in order to measure different feedings within a short time. This kit includes fast and safe connection possibilities, so that a power shut down is not necessary in most cases.
  • Fixed installation: The selected power feeding (415V) has to be shut down for approximately one hour in order to install the analyser box. Of course, a re-location into another feeding is possible at any time afterwards. The picture on the right shows the installation on the door of the power feeding (yellow box).

 

At the sample BOPP line, the power analyser was fixed installed at the feeding for utility, chill roll and MDO.

Results of the analysis

The power analyser provides a very detailed report. During the five months of the data acquisition at the sample line, the report shows that most of the reported events are within or close to the European norm. But it is apparent that the weak point of this power supply is the impact of power dips. Therefore we shall focus on the analysis of the voltage deviations.

 

The chart below shows the number of events with regard to voltage deviations. It records all voltage events with a maximum duration of 1 second and their deviation from the 100% line. Each yellow dot symbolizes one voltage deviation event. The red lines mark the limits of the European norm EN50160 (+/- 10 %). All electrical equipment is designed to work properly within these limits.

 

Of interest are all voltage dips below the red line at 90%. Each of them could cause a line stop. At the sample line, seven of these events definitely did!

Solution for voltage deviations

In order to avoid line stops caused by voltage deviations, the solution for the sample line would be an Active Voltage Conditioner (AVC). The AVC protects the plant power supply against excess and under voltage via a continuous voltage control. The effect of the AVC is symbolized by the blue dots in the chart above. They stand for voltage correction to each single yellow voltage dip or peak. Most of the voltage deviation could be corrected to 100%.

 

However, three voltage dips were dramatically lower than 70% at the sample line (no. 1 in the chart). Nonetheless the AVC could shift these events up to more than 95% (no. 2), i.e. within the limits of the European norm.

 

Using an Active Voltage Conditioner, the reported voltage deviations would not have stopped production.

Do you suffer from unstable power supply?

Please contact your Regional Service Manager or send an email to servtec@brueckner.com for more information about power analysis and the Active Voltage Conditioner (AVC).