151 research outputs found
Recommended from our members
Thermal Evaluation of High Voltage Hermetic Motors Experiencing Recurrent Insulation Failures
A high voltage hermetic compressor motor design developed for chiller applications has shown recurrent insulation failures in certain stator end-turn regions. Initial investigations found discoloration of failed coil insulation and suggested that the stator coils over heated during operation at rated load. Thermal modeling was conducted to develop an understanding of the causes of the unacceptably high motor failure rate so that corrective actions could be taken for future motor designs. This paper presents thermal modeling efforts for predicting steady-state temperature distributions within the stator coil in the end-turn region under full-load electrical heating and a refrigerant cooling environment. Insulation thermal conductivity and coil surface convection heat transfer coefficient were identified as two critical heat transfer parameters which dictate the effectiveness of coil heat dissipation. Thermal analysis results have been correlated with measured temperature dependent insulation thermal conductivities and stator coil surface temperatures measured in motor cooling tests. The results of thermal evaluation indicate that the premature motor failures are likely caused by excessive conductor heating due to high operating current density in a non-uniform coolant distribution.Center for Electromechanic
Recommended from our members
Rotating Machine Technologies for Integration of Pulsed and High Power Loads in Naval Electric Power Systems
Advanced electric sensors and weapons are placing increasing demands on the electric power distribution systems of future naval vessels and energy storage is viewed as a critical technology for effective integration of IPS architectures in these platforms. This paper shows that kinetic energy storage, i.e. stored in the angular momentum of a rotating mass, can be applied in differing topologies to address a range of ship power system applications. Rotating machine technologies are presented for UPS and load leveling applications as well as for high cycle rate pulsed power applications.Center for Electromechanic
Recommended from our members
Electric power system concepts for integration of advanced sensor and pulsed loads in the DDG-51 class ships
Advanced weapons and sensors increase demand on the electric power systems of Navy surface combatants, driving the need for fully Integrated Power Systems (IPS) such as those found in the DDG-1000 Zumwalt class of ships. The goal of this paper is to introduce novel power system configurations that could potentially be integrated into future flights of the DDG-51 class to support expanded electric power system capability at reasonable cost. Two concepts are presented: the first addresses the need for additional power for advanced sensor systems and the second addresses the need for a more significant increase in capacity to support higher power electric loads.Center for Electromechanic
Recommended from our members
High speed induction motor and inverter drive for flywheel energy storage
The use of flywheels to store energy is a technology which is centuries old. The confluence of several modern technologies has resulted in flywheels becoming a viable solution for the needs of the transportation, electric utility, and aerospace industries. This paper discusses a high-speed induction motor and its associated inverter drive which were developed for the Federal Railroad Administration’s “Advanced Locomotive Propulsion System.” The design of the induction motor provided several significant challenges. A megawatt rated, 12,000 rpm motor operating at a rotor surface velocity speed of 230 m/s required a unique mechanical configuration to withstand the centrifugal forces as well as an electromagnetic design, which produced a high efficiency at 200 Hz. Extending the design practices used in smaller motors would not achieve the goals required for a megawatt size machine. Similarly, the inverter was developed using a soft switching technique in order to meet the demands of high power output in a compact package. Application requirements, electrical and mechanical features of the motor, design strategy for the inverter, and test results are all presented in this paper.Center for Electromechanic
Recommended from our members
MVDC and HFAC Electric Power System Architectures for the Transformable Sea Base Connector (T-Craft)
The paper presents high frequency ac (HFAC) and medium voltage dc (MVDC) power system architectures for a notional T-Craft concept design and provides a qualitative comparison of relevant performance parameters. In particular the following items are discussed as worthy of attention in view of the large potential benefits they could produce: Risk mitigation in operating multiple series and parallel connected power conversion modules for both rectification and inversion at multi-megawatt power levels and high peak operating frequency. Synchronous drive topology offering the potential benefit of eliminating the need for multi-megawatt power conversion without compromising capabilities or performance: this would significantly reduce risk by eliminating much of the power electronics and the attendant size, weight and cost. Circuit protection strategies and components, for either HFAC or MVDC, for a flexible architecture suitable for fault management and reconfiguration. Integration of compact, lightweight gearboxes, either conventional planetary or advanced magnetic gear type, with existing designs for high-speed motors at the power level required by T-Craft. Critical technical issues for each power system architecture are identified and proposed simulation and technology development activities are described.Center for Electromechanic
Recommended from our members
Status of the Advanced Locomotive Propulsion System (ALPS) Project
The University of Texas at Austin Center for Electromechanics (UT-CEM) is currently developing an Advanced Locomotive Propulsion System (ALPS) as part of the Next Generation High Speed Rail program sponsored by the Federal Railroad Administration (FRA). Testing of the advanced propulsion system will be conducted as a portion of the FRA Non-Electric High Speed Locomotive Demonstration program. The project goal is to develop a non-electric locomotive propulsion system capable of 150 mph operation on existing infrastructure with good fuel economy and low noise and pollutant emissions. The propulsion system consists of two major elements: (1) a high speed generator directly coupled to a 5,000 hp gas turbine (turboalternator) to provide prime power and (2) an energy storage flywheel to provide additional power for acceleration and speed maintenance on grades, and to recover kinetic energy during braking. In addition to improving the overall system efficiency, the energy storage flywheel also provides load leveling for the turbine, reducing thermal cycling and significantly extending turbine maintenance intervals. The paper provides an overview of the ALPS system and presents the results of performance simulations to illustrate the benefits of the system. The paper also provides the current status of the project, along with component test results as available.Center for Electromechanic
Recommended from our members
Critical Design Factors in the Development of a Hybrid Electric Advanced Locomotive Propulsion System
Hybrid electric propulsion systems have been applied to a range of vehicles, from compact passenger cars to transit buses and rail vehicles. These systems offer improved performance, increased fuel efficiency and reduced emissions. The University of Texas at Austin Center for Electromechanics (UTCEM) is developing a hybrid electric propulsion system for high speed non-electric passenger locomotives as part of the Federal Railroad Administration’s Next Generation High Speed Rail program. The Advanced Locomotive Propulsion System (ALPS) project, introduced at the Fall VTC-2003 conference, seeks to demonstrate technology for a fossil fueled hybrid-electric locomotive propulsion system capable of operation at speeds up to 150 mph on existing infrastructure with acceleration comparable to current generation electric locomotives. Lightweight, high performance fossil fueled locomotives will facilitate the expansion of high speed passenger rail by providing energy efficiency and trip times comparable to electrified systems without the $3-5M per track mile cost of electrification.Center for Electromechanic
Recommended from our members
Intelligent Microgrid Demonstrator
The Center for Electromechanics at the University of Texas at Austin has a microgrid demonstrator capable of operating at power levels up to 2 MW. The microgrid is designed to interface with the commercial power system and other distributed sources of electric power, both ac and dc. It incorporates local prime movers that drive generators, both conventional 60 Hz and high frequency ac (800 Hz), as well as energy storage units. The microgrid is designed as a flexible system, easily expandable in power and re-definable in terms of voltage levels and system configuration. Several grid architectures have been studied and simulated, including a variety of pulsed and intermittent duty loads, as they can be found on US Navy ships. One problem under investigation is that of dc bus stability under the influence of constant power loads: these loads are known to induce instability at kW power levels but experimental data is very limited at MW power levels which are more representative of the situation on a ship. This paper describes the microgrid architecture, simulation results and data collected to date, as well as plans to demonstrate critical issues like stability, reconfigurability, fault management, integration of renewables, and model validation.Center for Electromechanic
Evaluation of the SUNHEART Cardiology Outreach Programme
Introduction: The demand for advanced cardiac care and specialised interventions is on the increase and this results in bottlenecks and increased waiting times for patients who require advanced cardiac care. By decentralising cardiac care, and using a hub-and-spoke model, the SUNHEART Outreach Programme of cardiovascular care aims to improve access to advanced cardiac care in the Western Cape. Tygerberg Hospital is the central hub, with the fi rst spoke being Paarl Hospital. Objective: To determine the value of the SUNHEART Outreach Programme to the public health care system. Methods: An audit of patients accessing the OutreachProgramme was performed for the period May 2013 - May 2014 and consequently compared to a historical cohort of patients accessing the health care system during the preceding 6 months, from October 2012 -April 2013. Access to advanced cardiac care was measured in time to initial evaluation, time to defi nitive diagnosis or intervention and patient compliance with appointments. The value to the health care system was also assessed by performing a cost analysis of transport of patients and health care workers, as well as compliance with appointments. We documented the spectrum of disease requiring advanced cardiac care toguide future interventions. Results: Data of 185 patients were included in the audit. Sixty four patients were referred to tertiary care from October 2012 - April 2013 and 121 patients were referred to the outreach facility from May 2013 - May 2014. There was a signifi cant reduction in waiting times with the median days to appointment of the historical cohort being 85 days compared to 18 days in the Outreach Programme cohort (p<0.01). Patient compliance with appointments was signifi cantly superior in the Outreach Programme cohort (90% vs. 56%: p<0.01). Valvular (36.5%) and ischaemic heart disease (35.5%) were the major pathologies requiring access to cardiac care services. Transport costs per patient treated was signifi cantly reduced in the outreach programme cohort (R118,09 vs. R308,77). Conclusion: Decentralisation of services in the form of an Outreach Programme, with a central hub, improves access to advanced cardiac care by decreasing waiting time, improving compliance with appointments and decreasing travel costs
Recommended from our members
Advanced Induction Motor End Ring Design Features for High Speed Applications
This paper presents advancements in induction motor endring design to overcome mechanical limitations and extend the operating speed range and joint reliability of induction machines. A novel endring design met the challenging mechanical requirements of this high speed, high temperature, power dense application, without compromising electrical performance. Analysis is presented of the advanced endring design features including a non uniform cross section, hoop stress relief cuts, and an integrated joint boss, which reduced critical stress concentrations, allowing operation under a broad speed and temperature design range. A generalized treatment of this design approach is presented comparing the concept results to conventional design techniques. Additionally, a low temperature joining process of the bar/end ring connection is discussed that provides the required joint strength without compromising the mechanical strength of the age hardened parent metals. A description of a prototype 2 MW, 15,000 rpm flywheel motor generator embodying this technology is presentedCenter for Electromechanic
- …