| 1. |
- Amlinger, Hanna, et al.
(author)
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Operational deflection shapes of a PWM-fed traction motor
- 2016
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In: Conference Proceedings of the Society for Experimental Mechanics Series. - Cham : Springer. - 9783319300832 ; , s. 209-217
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Conference paper (peer-reviewed)abstract
- Operational deflection shapes of an asynchronous traction motor for railway applications are investigated. The radiated noise from the tractionmotor on a train is, especially at low speeds, dominated by noise generated by electromagnetic forces. The tested motor is fed by a pulse-width-modulated (PWM) frequency converter for which the voltage is modulated as a series of pulses that are switched with a certain frequency. In this case, PWM force lines can be expected to influence the radiated noise. Therefore, detailed knowledge about the frequencies and deflection shapes of vibrations generated by PWM forces is of great importance for understanding and controlling the radiated noise and its spectral content. Vibration levels are measured on the stator shield and the operational deflection shapes are studied for several PWM switching frequencies and motor speeds. The deflection shapes with the largest vibration levels are determined. These are then compared to the expected excitation resulting from the pure PWM force lines. Changing the switching frequency, will shift the frequencies of the exciting forces. An appropriate selection of the PWM switching frequency is therefore important for the resulting acoustic radiation from the motor.
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| 2. |
- Botling, Fredrik, et al.
(author)
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Vibro-acoustic modal model of a traction motor for railway applications
- 2016
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In: Conference Proceedings of the Society for Experimental Mechanics Series. - Cham : Springer. - 9783319300832 ; , s. 197-208
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Conference paper (peer-reviewed)abstract
- A vibro-acoustic modal model of a traction motor for railway applications is presented based on an experimental modal analysis of the system. Noise requirements for railway traction motors are getting more and more demanding as part of the overall levels of new rolling stock. It is therefore of great interest to understand and predict the vibro-acoustic behaviour of electromagnetic noise generated by traction motors. The modal parameters are derived from an experimental modal analysis. The primary source for the radiated sound of the tested traction motor is the radial deflections of the stator shield. The modal parameters for the radial deflections are implemented in a reduced order modal model in a state space format using Matlab/Simulink. Only the structural modes that have a match in both the frequency and the spatial domain with the excited electromagnetic force will cause important vibro-acoustic response. This makes it possible to create an accurate and efficient reduced order modal model with only a fraction of the total number of structural modes. The simulation results from the modal model are compared to measurements of operational deflection shapes and acoustic measurements of the motor.
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| 3. |
- Brandt, Anders, et al.
(author)
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Flipping the classroom for a class on experimental vibration analysis
- 2016
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In: Rotating Machinery, Hybrid Test Methods, Vibro-Acoustics & Laser Vibrometry, Volume 8. - Cham : Springer. - 9783319300832 - 9783319300849 ; , s. 155-159
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Conference paper (peer-reviewed)abstract
- Flipped classroom is a relatively new teaching form in higher education which is aimed at improving the learning process by engaging students in pre-class video activities fostering more active discussions between lecturer and student in-class. The concept is that the students watch recorded lectures (lower-order thinking skills) at home prior to class. During the class the students work on assignments and discuss the course content which can make better use of the teacher as a facilitator, so the focus can be on the more difficult things (higher-order cognitive skills) in the course content. In the present paper, the design and implementation using the flipped classroom technique for a course on experimental vibration analysis is presented. Some important experiences are discussed and an evaluation of student experiences is presented. The outcome is that the teaching technique is relatively time consuming to implement, but that the students appreciate being able to watch the lectures at their own pace and having more time working with the difficult things together with the teacher. Also, it turned out that the way the videos were used was very different among different students.
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