ECE – 590 I POWER & ENERGY SYSTEMS SEMINAR
WHEN: Monday, November 18, 2024
WHERE: ECEB 4070, 3:00 – 3:50 p.m.
SPEAKER: Joshua Feldman, Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign
TITLE: "Study of Flow-Boiling Liquid Nitrogen for Use in Cryogenic Motor Cooling"
ABSTRACT: Cryogenic cooling of motors can increase specific power and power density by reducing the winding resistivity or enable superconducting windings. Proper thermal modelling of cryogenic motors requires experimentally verified correlations for predicting convective heat transfer coefficient (HTC) of the cryogenic fluid. For flow-boiling fluids, some correlations exist but can have widely varying predictions. Furthermore, no correlations exist for tubes which are partially heated or coiled.
Here we present results from an experiment to measure the HTC of flow-boiling nitrogen in a straight, uniformly heated tube. The results will serve to improve the accuracy of flow-boiling correlations for liquid nitrogen. The results will also serve as a baseline for future experiments measuring the HTC of flow-boiling nitrogen in partially heated and coiled tubes. It is our hope that these results will improve thermal modelling accuracy of cryogenic motors.
SPEAKER: Anuj Maheshwari, Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign
TITLE: "Dual-Use of Onboard Chargers to Achieve Controllable DC Bus Voltage for Variable Pole Induction Motors in Traction Applications"
ABSTRACT: Drive train efficiency and power density are crucial in improving the range of electric vehicles. Variable pole induction machines (VPIMs) have been shown as a viable replacement for permanent magnet motors. They can achieve the torque speed requirement of electric vehicles even at high speeds without oversizing the drivetrain. However, the torque speed envelope shrinks when the battery voltage drops as the battery discharges and consequently a dc-dc converter is needed to meet the torque speed requirement. Instead of using a separate fully rated dc-dc converter, we propose using the already present on-board charger to control the inverter dc-bus voltage. The onboard charger is reconfigured into a partial power processing converter to control the dc-link voltage using a double pole double throw (DPDT) switch. The proposed architecture not only removes the need of separated dc-dc converter increasing the power density of the drive train but also enhance the efficiency as the converter only processes part of the power consumed in the motor.