Investigation of a New Test Method to Perform a Vibration Test on Alternators

Sammanfattning: This master thesis work was performed in the Scania RECT group. The purpose of this study was to investigate a new test method and to examine if it was possible to perform a vibration test on two alternators at the same time where one would act as a motor and the other as a conventional alternator. That all electric machines can be run both as a motor and a generator was nothing new. But the question was whether it was possible to put a load on the motor with enough good results to perform a vibration test. Among other things, in order to verify that subcontractors conform to Scania’s life length requirements, these types of vibration tests are routinely performed. Previous tests have shown that there have been some problems to perform a vibration test during operation. This due to low belt tension and unwanted resonances in the system. After thorough analysis of different control systems a controller to try to get the generator to rotate was purchased. First tests showed that it was possible to operate the alternator as an electric motor. Thereafter the new electric motor was paired with a similar alternator via a belt to start loading the original alternator. Two alternator types were investigated, one that worked significantly better in terms of testability than the other and the decision was taken to only use the better during the final vibration test. To the final test a completely new test rig was constructed to run new converted alternators in the future. Also, a fixture compatible with the bottom plate where the shaker test is performed was designed for future tests of alternators. Final vibration test resulted in several interruptions where the tested alternator broke down several times at the given PSD level and the final test could not be completed. However, it could be concluded that the new test method worked very well and can be used for future vibration tests of alternators.