Sensor technology for middle-detection of roebel-bars
Ergebnisse aus dem Projektseminar wurden unter dem Titel "Segmentierung von Oberflächen auf Basis der lokalen Reflexionsindikatrix" im Tagungsband "Optosensorik in der Produktion, 2006" veröffentlicht.
The austrian company VA Tech Hydro, Weiz, manufactures so-called roebel-bars for electric machines. These bars are required to prevent the skineffect in the stator coil. It is important to know the center of the bar for the exact assembly of the bars into the stator.
Because the bars are isolated, the detection process must be able to interfuse the isolation without damaging it.
The following detection methods were tested:
- electro magnetism
The idea is to mount a marker just underneath the isolation layers, so that it’s possible to locate the attached marker accurately. The company confirms that it is allowed to attach markers prior to the isolation process. These markers must meet the following criteria:
- Their height must not exceed 1 mm, otherwise the isolation may be affected.
- The detection properties of the marker should not be destroyed by the isolation process involving high temperature.
- The marker remains underneath the isolation layers, therefore the functionality of the bar must not be affected.
After a few tests magnetic markers were selcted as method of choice, because detection is simple and it is safe for the environment and the user.
Furthermore measurements with a permanent magnet marker and a magnetoresistive sensor and also marking with an electro magnet and pancake coils were examined. The measuring setups and measurement results of these two principles are shown in figure 1 and figure 2. Both of these measurement principles can be realized, so they are presented in the documentation.