A framework for dynamic characterization and short-term thermal capability assessment of electric machines and inverters in motor drives.

摘要

The need for more powerful and compact motor drives is growing, especially in the fields of automotive traction and more-electric aircraft systems. These applications have peak-duty aspects that intermittently stress the drive. To account for this stress, conventional methods dating back to the 1940s have yielded oversized and expensive designs. This dissertation presents motor-drive characterizations to illuminate the full extent of their peak capabilities and control strategies to safely attain peak torque.;Vector-controlled induction machine torque capabilities are assessed and limiting factors are investigated. Static and dynamic thermal characterizations are carried out through analytical and experimental approaches. Three decoupled heating regimes that characterize time ratings ranging from modest to severe overloads are identified. The characterizations show that recent general-purpose open-drip-proof induction machines can handle up to 25 times more heat dissipation than rated for 30 seconds and twice the rated heat dissipation for 60 minutes. A self-limiting control strategy is developed that exploits these capabilities and protects the drive from overheating. Results suggest that these machines may be safely overloaded even after the hot-spot temperature limit is reached, as long as internal temperatures are below rated. Inverter sizing to accommodate peak duty is also addressed and design tradeoffs on size and short-term ratings are highlighted.;These characterizations inform an energy-based and service time-aware design strategy which allows size reduction of up to 70% in automotive drives and 17% in aircraft actuators. Analyzing the general-purpose motors from a peak-duty perspective shows that they have significant time-limited peak capabilities---with no structural change, they provide high short-term power density. Once fully exploited, this peak capability makes possible inexpensive and compact drive systems for the tomorrow's advanced applications.