Last edited one month ago
by Max Mustermann

Corona Grounding (2)

Template:Infobox bms


1 Grounding Corona Rolls[edit | edit source]

The Corona treatment is necessary to modify the molecular structure of the surface of the film to change its wettability and chemical affinity. It makes it possible for further treatment like printing labels or cluing as an example. Corona treatments are done with static load by HV-generators and electrodes nearby the film at voltages within the range of 10-20kV AC and a frequency from 10-60kHZ.

To protect the bearings at the corona rolls it is very important to check their grounding because if there is a bad or even no electrical connection, the discharge current goes over the bearing and it gets damaged faster. Inproper grounding can cause harm to humans due to high touch voltage between electrical components like motors and different machine parts as well. With the proper grounding we want to reduce this current over the surface of the bearing and protect humans health as well.

Each Corona roll has two ceramic insulated bearings.

Both operator side and drive side are equipped with a SCHUNK unit, which consists of two carbon brushes that close the electrical connection with the roll shaft.

2 Common Problems[edit | edit source]

2.1 Installation of the Shunk-Mountings[edit | edit source]

There is a microswitch installed which signals if the carbon brushes are reaching their minimun length.

Please have a look at the copper wires in the pictures above. They shall be connected like pictured using the two smaller mounting screws. (The mounting screws can be used because there is almost no weight on them)

If different connection screws are used, the wires might get too short, therefore the microswitch could never be activated.

3 Assembly notes[edit | edit source]

  • Also please note that there is an arrow on each of the carbon pieces, which signals the direction of roll's rotation.
  • Do not mix the two carbon brushes: The copper wires must be on the "inside" of the unit.
  • During BSK assembly the brushes were adjusted correct and with a sandpaper on the shaft, the radius will be created!

File:SchunkUnit arrow wires.png


From each non-switchable generator there must be three grounding connections:

  • One to the machine frame
  • One to Schunk OS
  • One to Schunk DS

Each switchable generator must have these grounding connections:

  • One to the machine frame
  • One to Schunk OS on roll 1
  • One to Schunk DS on roll 1
  • One to Schunk OS on roll 2
  • One to Schunk DS on roll 2

On each Corona Roll there must be:

  • A connection from Schunk DS to Schunk OS


File:CoronaGroundingOVW.png

At each change and after installation, check if the correct Brushes were installed:

  • 589410: Brushes for <180kW Generators (Combined Power); "S13 F19" Written on the brushes
  • 5003356 Brushes for >180kW Generators (Combined Power) "S30" Written on the brushes

4 Adjustment of the Brushes[edit | edit source]

  • The new adjustment Plate will be in the end of 2025 on site.
  • New metal plate (red highlighted) which will be designed for each roll shaft.
  • The Brush holders are automatically in the correct angle.
  • There are long holes now, that you can move the complete holder easy in and out or take i out to change the brushes.
  • You should move it completely inside, until the red plate touches the roll shaft
  • The plate stays during production insides. You should not remove it!

File:SchunkUnit AdjustmentLongHole.jpg File:SchunkUnit AdjustmentPlate.jpg

5 The tasks:[edit | edit source]

  • The carbon brush at the "SCHUNK" unit should be grinded into the shaft and at least aligned properly.
  • The shaft and the carbon must be clean, means free of dust, grease or metal parts. An arrow indicates the direction of the rotation of the roll.
  • The resistance between the shaft and the copper bar should be not more than 0.1 Ohm! Please consider this when measuring for the protocol.
  • Wiring PE: All outgoing grounding cables must be connected to the copper bar inside the generator and NOT to the grounding screen at the HV transformer


File:CoronaGroundingHVTransformer.png

  • This cable, Type ESUY 16mm², is high flexible and certified for the use of high voltage, high frequency applications and looks like similar to this:
      ESUY high flexible PE


  • Measure resistance according to the protocol attached below - It should be done without cooling water inside the PRS rolls.
  • Commissioning of Corona stations by MERO technician including connecting HV-cables. He has to check the grounding and should mention it in his protocol as well done.

NOTE that the resistance values required have changed in the grounding protocol from 10MOhm to 0.5MOhm.

File:Messprotokoll, Isolierung COR-Walze 467685 001 06.pdf

5.1 Info[edit | edit source]

  • make sure the PT100 at the water intake of the roll is not shielded or grounded at the sensor side. It would work as a short circuit as well.
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