STAR-CCM+ and SPEED for electric machines cooling analysis. Stefan Holst

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1 STAR-CCM+ and SPEED for electric machines cooling analysis Stefan Holst

2 Overview SPEED s own thermal capability consists of simplified circuit models Good for a first shot Circuit model allows for quick analysis of duty cycle simulations Efficiency requirements, space and weight restrictions lead to more complex machine and machine enclosure designs Identifying hot spots becomes tricky STAR-CCM+ can show its strength in these models User should benefit as much as possible from the work done in SPEED Import geometry Import distribution of heat loads electromagnetic losses Future: coupled EMAG and thermal analysis in a single tool

Loss mechanisms and distribution Ohmic heating in all conducting parts Windings, laminated rotor and stator core and magnets Winding/copper losses are usually the largest

3 Loss mechanisms and distribution Ohmic heating in all conducting parts Windings, laminated rotor and stator core and magnets Winding/copper losses are usually the largest contributor Hysteresis effects mostly in steel parts Simulation these effects directly requires coupled transient EMAG run Very costly for a design calculation Note: Losses occur locally

Steinmetz Loss calculation Alternative to

positions and attribute losses to size of field

4 Steinmetz Loss calculation Alternative to coupled simulation Hysteresis and eddy currents are mostly driven by changes in the magnetic field Get magnetic field for various rotor positions and attribute losses to size of field changes Strong variation in the teeth Magnets shield the rotor core

5 Workflow diagram Initial 2D Machine Layout Perform EMAG layout Perform thermal circuit simulation of duty cycles nodes Geometry Import Meshing automatically specified Physical setup Either CHT Or EMAG Or even coupled Heat Loads from SPEED Import via STAR-CCM+ file format *.sbd Surface data needs to be mapped to volume

6 Geometry import xgdf & xdef files contain the complete EMAG setup in XML Currently only Geometry import Future versions include physics and models for end-windings, skew

7 Cooling mechanism Air cooled Exterior and interior Spray cooling of the end windings Water cooling around the stator More on that now

8 Results for a cooling jacket around the stator Heat conduction, convection and radiation in the interior air 1l/min water pumped through How to keep the rotor cool?

9 Introduce holes into the rotor Four CAD features later we ve got holes in the rotor Remesh and further iterating gives

Data Mapper Losses are given in 2D but the thermal simulation is in 3D Data Mapper functionality extension to facilitate precise mapping even for skewed machines will come with 7.

10 Data Mapper Losses are given in 2D but the thermal simulation is in 3D Data Mapper functionality extension to facilitate precise mapping even for skewed machines will come with 7.04 Improved mapping quality compared to current nearest neighbour interpolation Three mappings are defined here: Rotor Stator Windings SPEED only provides total losses in magnets

11 Support for end windings Examples so far have been hand made 3D CAD constructions

12 Glimpse on the EMAG solver Magnetostatic runs for different rotor positions

transient and magnetostatic mode Magnetostatic can be coupled with motion to cater for loss calculations Non-linear

13 Glimpse on the EMAG solver Low frequency electro-magnetic solver Frequency/domain size determines applicability An e-machines frequency range might not be allowed in areas like mine detection with far larger length scales Coupled transient and magnetostatic mode Magnetostatic can be coupled with motion to cater for loss calculations Non-linear material support SPEED model import brings in BH-curves Tabular data or functional description Isotropic electric conductivity and permeability

electromagnetic circuit elements Field simulation Hysteresis modeling Residual

14 EMAG solver outlook Circuit Transient 3D requires feedback from the circuit Extend circuit capability in BSM for general use Flux linkage report for electromagnetic circuit elements Field simulation Hysteresis modeling Residual magnetism Force/Torque calculation Anisotropy Electric conductivity and permeability Infrastructure

15 Thank you Thank you!

The use of Simulation in Electric Machine Design Stefan Holst, CD-adapco

The use of Simulation in Electric Machine Design Stefan Holst, CD-adapco Motivation How often can a machine be started within an hour In Hybrids, what effect has the adjacent combustion drive train Space