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Cooling of Electrical Machines



Electrical machines like transformers, motors and generators have a high efficiency; however the electrical losses reach such high levels that the produced losses must be removed through an appropriate method.  The life expectancy of the winding isolation strongly depends on temperature, an increase of the temperature level by 5 to 8 K results in a halving of the life expectancy.  As the winding resistance is temperature dependant, an improvement of the cooling would bring about a decrease on the copper losses.  Due to the high material costs, it is desirable to use this to its limit: through a more efficient cooling process the current density can be increased and as a result the same machine size can reach a higher power.

The flow and thermal processes in a large motor or generator are highly complicated and they cannot be well described with the older methods. Measurements inside a fast rotating rotor are very complicated due to the high circumferential speed.  The 3D Computational Fluid Dynamics is the correct alternative for the analysis, concept and for the detailed design of electrical machines as it allows to precisely predict the flow structure around the stator coil ends, the distribution of the cooling medium, the pressure losses, the heat transfer coefficients and temperature distribution.  Without an extreme simplification of the geometry, a coupled thermal and flow calculation for the complex geometry of a stator in the coiler head is only possible with software based on Cartesian mesh like FloEFD.

What You Will Learn

  • Why large electrical machines need cooling
  • How to conduct thermal analysis starting from a CAD model
  • How to input the electrical losses in a FloEFD model
  • Why FloEFD is well adapted for the thermal design of electrical machines

About the Presenter

Presenter Image Karim Segond

Karim Segond studied Mechanical Engineering in Toulouse and then later in Berlin, where he worked at Siemens Large Drives where his main tasks were 3D thermal and flow calculations for a synchronous motor with turbo rotor. After obtaining his Masters, he worked in Alstom Power in Baden as an aerodynamics engineer on the development of new low pressure steam turbines. He also worked for ABB Minerals in Switzerland on a short term contract looking at 3D Thermal and Flow Calculations for electrical motors. He now works as a consultant for cooling calculations of electrical equipment. Karim can work with the market leading CFD software. However he prefers to work with software based on cartesian mesh, like FloEFD, as it allows for easy set-up and fast heat-transfer cases, resulting in lower costs. By using these tools, Karim offers a distinct competitive advantage over many of his customers who are still using older tools.

Besides electrical machines, Karim also investigates thermal management of power electronics components used to drive large engines. Here CFD can be used to optimized the design and ensure the best possible cooling for the components. He has also turned his attention to the overall cooling of a system; such cooling systems that are too big and too complex to simulate with 3D CFD software. Therefore, it is necessary to analyze them using a 1D thermal and fluid flow circuit that is modeled in a 1D CFD tool such as Flowmaster. This combined solution then enables Karim to provide the qualities of both tools and provide the ultimate cooling solution to his customers.

Who Should View

  • Design Engineers
  • Mechanical Engineers
  • Design Engineers
  • Anybody who is using CAD in the electrical industry

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