Abstract
Research and/or Engineering Questions/Objective
Overheating in electrical motors results in detrimental effects such as degradation of the insulation materials, magnet demagnetization, decreased motor efficiency and lifetime. Hence, it is important to find ways of optimizing performance and reliability of electric motors through effective thermal simulation and consequently reduce operating and maintenance costs. Modern thermal simulation techniques can be classified into two general methods, thermal circuit and FEM method. Because the thermal circuit method can predict and optimize the motor thermal properties faster, it is more useful than the FEM method in the concept design phase of E-motor.
Methodology
This paper describes a thermal methodology for a permanent magnet synchronous motor by coupling 1D thermal circuit analysis with 3D CFD simulation.1D lumped parameter model is developed with a circuit of interconnected nodes, thermal resistances, thermal mass and heat transfer elements representing the heat processes within the IPM, it builds obviously refined thermal network model to accurately reflect the structure of the internal motor temperature gradient.3D nonlinear CFD simulation can not only obtain the heat transfer parameters for 1D thermal circuit model, but also provide heat source distribution and temperature rising result in E-motor assembly.
Results
We can obtain the detailed temperature distribution at different time by using 1D circuit thermal simulation. This is the supreme advantage of 1D circuit thermal simulation, also is the main purpose of this study. Both 1D thermal circuit and 3D CFD simulated results show good agreement with each other as well as available experimental results. Especially less computing time is used compared with the 3D simulation, so it is simple and fast to carry out sensitivity analysis using the 1D thermal circuit model to obtain their influence on the computation results of the model, and guiding the motor cooling system design.
Limitations of this study
In this study, the motor structures are divided into many areas which can reflect the temperature gradient. Each thermal mass represents a temperature region; we cannot get the temperature rise curve at a particular point, only use the average temperature results of particular region to compare with 3D CFD simulation and experimental results.
What does the paper offer that is new in the field including in comparison to other work by the authors?
Building up the detailed discrete thermal circuit model in this paper is new. The model can accurately predict and identify the temperatures of critical areas of the motor same as 3D FEM method, obtain heat transfer path and cooling mechanism between the major structures to optimize motor cooling design.
Conclusions
Detailed 1D discretization circuit model can completely overcome low resolution problem, obtain the detailed temperature distribution. Calculation speed is very fast by using 1D model to analyze the temperature of E-motor, this is very important when carrying out sensitivity analysis and calculating transient thermal analysis with complex operation cycle loads.
Key Words : Thermal simulation; Thermal circuit method; CFD; Interior permanent-magnet (IPM) motors