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VEM motors are part of the "Freiberg Colloquium Electrical Drive Technology"
From the diploma thesis to the colloquium
In cooperation with the VEM group, Justin Lehmann also contributed to the success of the two-day conference with the presentation "Simulation of thermal behavior of asynchronous traction motors in the load cycle". In a 45-minute lecture, Mr. Lehmann spoke about some of the results that he had compiled over the last six months as an external consultant for the group of companies.
His investigations were based on his diploma thesis "Modeling the heating of asynchronous machines taking into account any load cycles and variable cooling conditions". For this work, the graduate engineer modeled a heat source network that depicts the transient thermal behavior of traction motors. The components of the model characterized the heat exchange (heat conduction and convective resistance) as well as heat storage (heat capacities). The changing cooling conditions due to the speed were then determined using correlation equations.
The model was verified with several measurement-recorded heating runs in continuous operation with constant load (S1 operation) and different speeds. Any power losses that occur can be impressed on the node points of the corresponding components, which were previously localized by a very fine division in the radial and axial spatial directions. The node potential method was used to determine the temperatures of the individual nodes.
Collaboration with the VEM works
At VEM, Mr. Lehmann was able to apply the network to a drive with an analog cooling topology and a slightly modified geometry. He was able to prove that the model can be run not only for the drive from the diploma thesis, but also for a changed geometry - e.g. a changed laminated core length or number of cooling channels. Furthermore, in addition to S1 operation, the functionality of the model was also proven in short-term operation with constant load (S2 load).
The main task in all of these studies was to analyze the correct simulation of temperature curves during load cycles - i.e. changing speeds / torques. In this regard, a comparison of the calculated curves of the heat source network was carried out with two load cycles recorded by measurement. The basic thermal course of the measurements could be reflected here.
Further insights
In addition to the network for self-ventilated traction machines, Mr. Lehmann set up a heat source network for machines with a water jacket, with which investigations analogous to the diploma thesis were carried out. The networks developed are intended to function as part of the design process in the future. This makes it possible to simulate the expected temperature inside the drive and thus check compliance with the thermal class.
