Abstract
For identifying new improvement potentials for electric traction motors, accurate models are needed. In this paper, a geometry-based 2D lumped parameter thermal network model for different electric traction motor and cooling concepts is studied and validated. In the second section, the design and functionality of the thermal model is explained. In the third section, the best fit of the literature correlations for describing the different heat transfer mechanisms was identified and a parameter study of the heat transfer coefficients was carried out and discussed. In the last section, the model is validated with measurement results from six different electric traction motors and drives units. For validation measurement results of stationary operating points, peak operating points and drive cycles are used. Based on the validation results, a model error of less than 10% is achieved for the most motor components in the different cooling concepts and traction motor designs. Inaccuracies and deviations are discussed and suggestions for improvement are made.
Highlights
For many years, thermal models for electric motors have been used to calculate thermal behavior and lifetime expectancy of electric motors [1]
An example for a the error reason can be found in the motor #5 where the cooling system shows a big gradient in heat transfer behavior over the perimeter of the motor, because the thermal model does not predict local heat transfer differences over the motor perimeter
The experimental results show that the model can predict the motor temperatures of the different motor in an acceptable range of ∆Terror = ±10%
Summary
Thermal models for electric motors have been used to calculate thermal behavior and lifetime expectancy of electric motors [1]. A higher motor efficiency and lower energy consumption can be archived with better cooling systems This directly affects the range of the electric vehicle and the needed battery capacity, which directly affects the costs of the powertrain/vehicle. For fast early-stage development processes, lumped parameter thermal networks (LPTNs) are recommended because their can deliver fast and accurate results [1]. The quality of these results depends on the electromagnetic and geometric design of the motor and, on the heat transfer characteristics based on the geometric motor design. For validating the LPTN and the used HTC models a few different electric motors with different characteristics in their cooling systems are used. The model is validated by measurements of different stationary and peak operating points and drive cycles
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