Rotor cooling for asynchronous machines in highly dynamic applications

Highly dynamic electric asynchronous machines are used in testing and production systems due to their robustness. Their use is characterized by frequent torque changes, whereby a work cycle can also only comprise a single revolution. This results in special requirements for these drives. On the one hand, a rotor with a low moment of inertia is required, and on the other, the increased thermal loads compared to other machines must be safely removed. Conventional cooling systems do not adequately meet these special requirements. For this reason, a new concept with direct rotor cooling via radial cooling channels is being investigated, which enables heat dissipation closer to the heat sources.

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Due to the complexity of the overall machine, not all relevant phenomena can be resolved in time and simulated in combination with field calculation methods. For this reason, separate electromagnetic, solid mechanics and thermal simulations are carried out using FEM and CFD simulations with coupled heat transport in the solid. This allows relevant phenomena to be identified and analyzed under critical load conditions and during complete load cycles. Building on this, multi-physical simulations based on network modeling are carried out, which can also be used to analyze longer operating times. All simulation models are validated by model experiments. For this purpose, a disk model of the drive is used, which enables optical access to the radial cooling channels for optical measurements of the flow velocity and simulates the thermal conditions of the real machine.

The aim of the project is to create a fundamental understanding of the novel cooling system. In particular, the following research questions are to be answered:

• Where and when do thermally critical conditions occur in the drive? How can these be avoided?

• How great is the performance potential of the overall machine when using radial cooling compared to previous cooling methods? How can this be best exploited?

• What are the methodological limits of the simulation methods used and what is the model structure of the various methods for a cost-optimized simulation of the radial cooling of such a highly dynamic machine?