Thermal Analysis of Electric Motors for Automotive Applications - Seminario Spin all'Università dell'Aquila su software, elettrificazione e nuove frontiere della ricerca

1. Thermal analysis of electric motors
for automotive applications

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Thermal analysis
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Motors for automotive applications operate in a wide range of the torque-speed plane
Lumped-parameter models are needed for fast analysis
• Special motors and other devices  sT Activate (by Altair)
• Classical motors  Motor-CAD (by Motor-Design)

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Lumped-parameters thermal models
of classical motors
using Activate by Altair and Motor-CAD by Mdl
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• Squirrel-cage induction motors
• Permanent magnet brushless motors (inner and outer rotor)
• Switched reluctance motors
• Permanent magnet DC collector motors
• Wound rotor synchronous motors
• Claw-pole motors
• Single-phase squirrel-cage induction motors
• Wound-field collector motors
• Synchronous reluctance (SynchRel) motors
Available motor types

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Example: brushless motor
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Radial view Axial view

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Steady-state thermal analysis
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Drive cycle calculation with vehicle model
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Duty-cycle transient analysis power graph
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Duty-cycle transient analysis temperature graph
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Thermal envelope (max 160 °C on windings and 140 °C on magnets)
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Lumped-parameters thermal models
of special motors and other devices
using Modelica blocks in sT Activate
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INPUT DATA: POWERS
Thermal models generally require power injections or withdrawals as
inputs.
Powers Temperatures
Thermal
model
Power values can be obtained in several ways:
• Directly inserted by user as input data
• Evaluated by an electric circuit in Activate
(e.g. equivalent circuit of an IM)
• Read from a text file (e.g. “filename.csv”)
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Thanks to the txt/csv input file it is possible to take in account variable loss
profiles vs time
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PARAMETRIZATION
In order to have a powerful tool for thermal modelling, the Activate model is
fully parametrized: user has to insert geometric and physical data as inputs.
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Example: squirrel cage induction motor
The basic idea is to radially and axially divide the motor, forming annular
sectors each one with its own physical properties:
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Output transient temperatures: Motor-CAD validation
Motor-CAD radial view
Activate Motor-CAD
Temperature[°C]
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Example: axisymmetric electromagnet
The basic idea is to radially and axially divide the motor, forming annular
sectors each one with its own physical properties:
List of colors employed in the image:
Blue  moving core
Red  fixed core
Yellow  winding
White  airgap
Green  plastic sprocket
Turquoise  top disc
Brown  brass bushing
Purple  armatureR axis
Z axis
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Square-wave = 1
Electromagnet is turned ON
Moving core is pulled down
Square-wave = 0
Electromagnet is turned OFF
Wide airgap between cores
Activation
blocks
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The thermal behavior of the electromagnet is influenced by ON-OFF state,
as visible below.Temperature[°C]
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