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Permanent Magnet Direct Current Motor Thermal Simulation to Predict Its Temperature Rise during Eaton Automotive Rear Axle Differential Operation
Abstract:
Eaton’s automotive rear axle differential is used in vehicles to improve
stability while experiencing variable road conditions. It adjusts the power
ratio between wheels to reduce wheel spin and add understeer. A Permanent Magnet
Direct Current (PMDC) motor is used to develop hydraulic pressure, which is
converted into a bias torque across the axle.
Heat generated in a PMDC motor during transient operation can affect its torque
output due to changes in current. The variation in motor torque can impact the
rate at which hydraulic pressure is developed. Because of this, the differential
performance can be affected. A three-dimensional (3D) transient numerical
simulation methodology has been developed to predict temperature rise at
critical PMDC motor locations when subjected to a transient duty cycle. Heat
load required for simulation is calculated using motor current and efficiency
curve, thereby eliminating multi-physics simulation. Two modeling approaches,
Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD), are
described with their advantages and limitations. Model predictions agree with
literature findings and correlated with test data with 21°C deviation.