Abstract
This paper presents a finite element method (FEM)-based model, which describes the magnetic circuit of the BMW i3 traction machine. The model has been reconstructed based on data available in the public domain. The reader is provided with numerical data regarding flux linkage surfaces in d- and q-axes, as well as with all the information needed to develop a space-vector model of the machine in steady-state, taking into consideration the non-linearity of the magnetic circuit. Hence, the data of a highly-saturated machine from a renowned product are provided, which can serve as a reference design for research. After that, torque curve and partial load operation points are calculated. Finally, the machine model is linearized and the calculations are repeated with the simplified linearized model. The results from both models are then compared with each other. This comparison is intended to assess the magnitude of the expected inaccuracies, when simplified analytical tools are applied to highly-saturated machines (which are the backbone of automotive electrical drivetrains). It is especially important with regard to preliminary design of electrical drivetrains, as at this stage detailed machine geometry and materials are not known.
Highlights
The electric drive has been gaining popularity in the automotive industry over the past few decades
Over the years voltage-source inverter fed permanent magnet synchronous machines (PMSM) have become the backbone of traction drives, and drives mounted in auxiliary devices and actuators [1]
In order to meet these strict and often contradicting requirements, PMSM-based drives need to operate in the field-weakening mode and the machines are designed with highly-saturated magnetic circuits [1,2]
Summary
The electric drive has been gaining popularity in the automotive industry over the past few decades. As automotive applications impose very demanding requirements on drive performance, it has pushed research activities towards the development of highly-efficient, high-power-density, high-torque-density and at the same time cost-effective solutions [1]. In order to meet these strict and often contradicting requirements, PMSM-based drives need to operate in the field-weakening mode and the machines are designed with highly-saturated magnetic circuits [1,2]. Precise analysis of such drives requires complex magnetic field models based on a finite element method (FEM) simulation [3,4,5]. At the preliminary drivetrain design stage, machine dimensions and materials are not known and some simple analytic models are much more desired for this purpose [6]
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