Development of Integrated Modular Motor Drive for Traction Applications

This paper introduces a promising approach for developing an integrated traction motor drive based on the Integrated Modular Motor Drive (IMMD) concept. The IMMD concept strives to meet aggressive power density and performance targets by modularizing both the machine and power electronics and then integrating them into a single combined machine-plus-drive structure. Physical integration of the power electronics inside the machine makes it highly desirable to increase the power electronics operating temperature including higher power semiconductor junction temperatures and improved device packaging. Recent progress towards implementing the IMMD concept in an integrated traction motor drive is summarized in this paper. Several candidate permanent magnet (PM) machine configurations with different numbers of phases between 3 and 6 are analyzed to compare their performance characteristics and key application features. A 6-phase, 10-pole PM machine topology has been selected as the most promising configuration for meeting the major requirements in the areas of power density, efficiency, and module count. A parallel investigation of fault-tolerant distributed control configurations for the IMMD traction drive has led to selection of a heterarchical controller configuration that requires each phase module to be equipped with its own independent microcontroller operating as a peer with all of the other phase module controllers. The potential of silicon (Si) insulated gate bipolar transistors (IGBTs) operating at junction temperatures up to 200°C has been evaluated using a hardware testbed in terms of device losses and thermal issues. Based on these study results, a 10 kW phase-leg package design using Si IGBTs has been investigated including die selection, material selection, layout design, parasitic extraction and thermal characterization. Thermal performance characterization has been conducted for different packaging structures, operating conditions and coolant selections. The proposed packaging design and cooling approach can maintain the Si IGBT junction temperature below 200°C with an ambient temperature of 150°C.