Engineering topics

Kankam, M. David

Publications and source records attributed to Kankam, M. David.

16 records

NASA NTRS2007

Experimental Performance Evaluation of a High Speed Permanent Magnet Synchronous Motor and Drive for a Flywheel Application at Different Frequencies

This paper presents the results of an experimental performance characterization study of a high speed, permanent magnet motor/generator (M/G) and drive applied to a flywheel module. Unlike the conventional electric machine the flywheel M/G is not a separated unit; its stator and rotor are integrated into a flywheel assembly. The M/G rotor is mounted on a flywheel rotor, which is magnetically levitated and sealed within a vacuum chamber during the operation. Thus, it is not possible to test the M/G using direct load measurements with a dynamometer and torque transducer. Accordingly, a new in-situ testing method had to be developed. The paper describes a new flywheel M/G and drive performance evaluation technique, which allows the estimation of the losses, efficiency and power quality of the flywheel high speed permanent magnet M/G, while working in vacuum, over wide frequency and torque ranges. This method does not require any hardware modification nor any special addition to the test rig. This new measurement technique is useful for high-speed applications, when applying an external load is technically difficult.

Nagorny, Aleksandr S.↗

NASA NTRS2003

Glenn's Strategic Partnerships With HBCUs and OMUs

NASA senior management has identified the need to develop a strategy for increased contracting with the historically black colleges and universities (HBCUs) and other minority universities (OMUs). The benefits to the institutions, by partnering with NASA, include developing their industrial base via NASA-industry partnerships, strong competitive advantage in technology-based research opportunities, and improved research capabilities. NASA gains increased contributed value to the Agency missions and programs as well as potential future recruits from technology-trained students who also constitute a pool for the nation s workforce. This report documents synergistic links between Glenn Research Center research and technology programs and faculty expertise at HBCUs and OMUs. The links are derived, based on Glenn technologies in the various directorates, program offices, and project offices. Such links readily identify universities with faculty members who are knowledgeable or have backgrounds in the listed technologies for possible collaboration. Recommendations are made to use the links as opportunities for Glenn and NASA, as well as industry collaborators, to cultivate stronger partnerships with the universities. It is concluded that Glenn and its partners and collaborators can expect to mutually benefit from leveraging NASA s cutting-edge and challenging research and technologies; industry's high technology development, research and development facilities, system design capabilities and market awareness; and academia s expertise in basic research and relatively low overhead cost. Reduced cost, accelerated technology development, technology transfer, and infrastructure development constitute some of the derived benefits.

Kankam, M. David↗

NASA NTRS2001

A Survey of Power Electronics Applications in Aerospace Technologies

The insertion of power electronics in aerospace technologies is becoming widespread. The application of semiconductor devices and electronic converters, as summarized in this paper, includes the International Space Station, satellite power system, and motor drives in 'more electric' technology applied to aircraft, starter/generators and reusable launch vehicles. Flywheels, servo systems embodying electromechanical actuation, and spacecraft on-board electric propulsion are discussed. Continued inroad by power electronics depends on resolving incompatibility of using variable frequency for 400 Hz-operated aircraft equipment. Dual-use electronic modules should reduce system development cost.

Kankam, M. David↗

NASA NTRS1997

Speed Sensorless Induction Motor Drives for Electrical Actuators: Schemes, Trends and Tradeoffs

For a decade, induction motor drive-based electrical actuators have been under investigation as potential replacement for the conventional hydraulic and pneumatic actuators in aircraft. Advantages of electric actuator include lower weight and size, reduced maintenance and operating costs, improved safety due to the elimination of hazardous fluids and high pressure hydraulic and pneumatic actuators, and increased efficiency. Recently, the emphasis of research on induction motor drives has been on sensorless vector control which eliminates flux and speed sensors mounted on the motor. Also, the development of effective speed and flux estimators has allowed good rotor flux-oriented (RFO) performance at all speeds except those close to zero. Sensorless control has improved the motor performance, compared to the Volts/Hertz (or constant flux) controls. This report evaluates documented schemes for speed sensorless drives, and discusses the trends and tradeoffs involved in selecting a particular scheme. These schemes combine the attributes of the direct and indirect field-oriented control (FOC) or use model adaptive reference systems (MRAS) with a speed-dependent current model for flux estimation which tracks the voltage model-based flux estimator. Many factors are important in comparing the effectiveness of a speed sensorless scheme. Among them are the wide speed range capability, motor parameter insensitivity and noise reduction. Although a number of schemes have been proposed for solving the speed estimation, zero-speed FOC with robustness against parameter variations still remains an area of research for speed sensorless control.

Elbuluk, Malik E.↗

NASA NTRS1995

Motor Drive Technologies for the Power-by-Wire (PBW) Program: Options, Trends and Tradeoffs

Power-By-Wire (PBW) is a program involving the replacement of hydraulic and pneumatic systems currently used in aircraft with an all-electric secondary power system. One of the largest loads of the all-electric secondary power system will be the motor loads which include pumps, compressors and Electrical Actuators (EA's). Issues of improved reliability, reduced maintenance and efficiency, among other advantages, are the motivation for replacing the existing aircraft actuators with electrical actuators. An EA system contains four major components. These are the motor, the power electronic converters, the actuator and the control system, including the sensors. This paper is a comparative literature review in motor drive technologies, with a focus on the trends and tradeoffs involved in the selection of a particular motor drive technology. The reported research comprises three motor drive technologies. These are the induction motor (IM), the brushless dc motor (BLDCM) and the switched reluctance motor (SRM). Each of the three drives has the potential for application in the PBW program. Many issues remain to be investigated and compared between the three motor drives, using actual mechanical loads expected in the PBW program.

Elbuluk, Malik E.↗

NASA NTRS1995

Transient and Steady-state Tests of the Space Power Research Engine with Resistive and Motor Loads

The NASA Lewis Research Center (LeRC) has been testing free-piston Stirling engine/linear alternators (FPSE/LA) to develop advanced power convertors for space-based electrical power generation. Tests reported herein were performed to evaluate the interaction and transient behavior of FPSE/LA-based power systems with typical user loads. Both resistive and small induction motor loads were tested with the space power research engine (SPRE) power system. Tests showed that the control system could maintain constant long term voltage and stable periodic operation over a large range of engine operating parameters and loads. Modest resistive load changes were shown to cause relatively large voltage and, therefore, piston and displacer amplitude excursions. Starting a typical small induction motor was shown to cause large and, in some cases, deleterious voltage transients. The tests identified the need for more effective controls, if FPSE/LAs are to be used for stand-alone power systems. The tests also generated a large body of transient dynamic data useful for analysis code validation.

Rauch, Jeffrey S.↗

NASA NTRS1994

Controllability of Free-piston Stirling Engine/linear Alternator Driving a Dynamic Load

This paper presents the dynamic behavior of a Free-Piston Stirling Engine/linear alternator (FPSE/LA) driving a single-phase fractional horse-power induction motor. The controllability and dynamic stability of the system are discussed by means of sensitivity effects of variations in system parameters, engine controller, operating conditions, and mechanical loading on the induction motor. The approach used expands on a combined mechanical and thermodynamic formulation employed in a previous paper. The application of state-space technique and frequency domain analysis enhances understanding of the dynamic interactions. Engine-alternator parametric sensitivity studies, similar to those of the previous paper, are summarized. Detailed discussions are provided for parametric variations which relate to the engine controller and system operating conditions. The results suggest that the controllability of a FPSE-based power system is enhanced by proper operating conditions and built-in controls.

Kankam, M. David↗

NASA NTRS1992

Modelling a single phase voltage controlled rectifier using Laplace transforms

The development of a 20 kHz, AC power system by NASA for large space projects has spurred a need to develop models for the equipment which will be used on these single phase systems. To date, models for the AC source (i.e., inverters) have been developed. It is the intent of this paper to develop a method to model the single phase voltage controlled rectifiers which will be attached to the AC power grid as an interface for connected loads. A modified version of EPRI's HARMFLO program is used as the shell for these models. The results obtained from the model developed in this paper are quite adequate for the analysis of problems such as voltage resonance. The unique technique presented in this paper uses the Laplace transforms to determine the harmonic content of the load current of the rectifier rather than a curve fitting technique. Laplace transforms yield the coefficient of the differential equations which model the line current to the rectifier directly.

Kraft, L. Alan↗

NASA NTRS1992

A free-piston Stirling engine/linear alternator controls and load interaction test facility

A test facility at LeRC was assembled for evaluating free-piston Stirling engine/linear alternator control options, and interaction with various electrical loads. This facility is based on a 'SPIKE' engine/alternator. The engine/alternator, a multi-purpose load system, a digital computer based load and facility control, and a data acquisition system with both steady-periodic and transient capability are described. Preliminary steady-periodic results are included for several operating modes of a digital AC parasitic load control. Preliminary results on the transient response to switching a resistive AC user load are discussed.

Rauch, Jeffrey S.↗

NASA NTRS1992

Energy loss analysis of an integrated space power distribution system

The results of studies related to conceptual topologies of an integrated utility-like space power system are described. The system topologies are comparatively analyzed by considering their transmission energy losses as functions of mainly distribution voltage level and load composition. The analysis is expedited by use of a Distribution System Analysis and Simulation (DSAS) software. This recently developed computer program by the Electric Power Research Institute (EPRI) uses improved load models to solve the power flow within the system. However, present shortcomings of the software with regard to space applications, and incompletely defined characteristics of a space power system make the results applicable to only the fundamental trends of energy losses of the topologies studied. Accountability, such as included, for the effects of the various parameters on the system performance can constitute part of a planning tool for a space power distribution system.

Kankam, M. David↗

NASA NTRS1992

Dynamic analysis of Free-Piston Stirling Engine/Linear Alternator-load system-experimentally validated

This paper discusses the effects of variations in system parameters on the dynamic behavior of the Free-Piston Stirling Engine/Linear Alternator (FPSE/LA)-load system. The mathematical formulations incorporate both the mechanical and thermodynamic properties of the FPSE, as well as the electrical equations of the connected load. A state-space technique in the frequency domain is applied to the resulting system of equations to facilitate the evaluation of parametric impacts on the system dynamic stability. Also included is a discussion on the system transient stability as affected by sudden changes in some key operating conditions. Some representative results are correlated with experimental data to verify the model and analytic formulation accuracies. Guidelines are given for ranges of the system parameters which will ensure an overall stable operation.

Kankam, M. David↗

NASA NTRS1991

Development of a computer algorithm for the analysis of variable-frequency AC drives: Case studies included

The development of computer software for performance prediction and analysis of voltage-fed, variable-frequency AC drives for space power applications is discussed. The AC drives discussed include the pulse width modulated inverter (PWMI), a six-step inverter and the pulse density modulated inverter (PDMI), each individually connected to a wound-rotor induction motor. Various d-q transformation models of the induction motor are incorporated for user-selection of the most applicable model for the intended purpose. Simulation results of selected AC drives correlate satisfactorily with published results. Future additions to the algorithm are indicated. These improvements should enhance the applicability of the computer program to the design and analysis of space power systems.

Kankam, M. David↗

NASA NTRS1991

Development of a single-phase harmonic power flow program to study the 20 kHz AC power system for large spacecraft

The development of software is described to aid in design and analysis of AC power systems for large spacecraft. The algorithm is an important version of harmonic power flow program, HARMFLO, used for the study of AC power quality. The new program is applicable to three-phase systems typified by terrestrial power systems, and single-phase systems characteristic of space power systems. The modified HARMFLO accommodates system operating frequencies ranging from terrestrial 60 Hz to and beyond aerospace 20 kHz, and can handle both source and load-end harmonic distortions. Comparison of simulation and test results of a representative spacecraft power system shows a satisfactory correlation. Recommendations are made for the direction of future improvements to the software, to enhance its usefulness to power system designer and analysts.

Kraft, L. Alan↗

NASA NTRS1991

Development of an analytical tool to study power quality of AC power systems for large spacecraft

A harmonic power flow program applicable to space power systems with sources of harmonic distortion is described. The algorithm is a modification of the Electric Power Research Institute's HARMFLO program which assumes a three phase, balanced, AC system with loads of harmonic distortion. The modified power flow program can be used with single phase, AC systems. Early results indicate that the required modifications and the models developed are quite adequate for the analysis of a 20 kHz testbed built by General Dynamics Corporation. This is demonstrated by the acceptable correlation of present results with published data. Although the results are not exact, the discrepancies are relatively small.

Kraft, L. Alan↗

NASA NTRS1991

Comparative survey of dynamic analyses of free-piston Stirling engines

Reported dynamics analyses for evaluating the steady-state response and stability of free-piston Stirling engine (FPSE) systems are compared. Various analytical approaches are discussed to provide guidance on their salient features. Recommendations are made in the recommendations remarks for an approach which captures most of the inherent properties of the engine. Such an approach has the potential for yielding results which will closely match practical FPSE-load systems.

Kankam, M. David↗

NASA NTRS1990

An analysis of space power system masses

Various space electrical power system masses are analyzed with particular emphasis on the power management and distribution (PMAD) portion. The electrical power system (EPS) is divided into functional blocks: source, interconnection, storage, transmission, distribution, system control and load. The PMAD subsystem is defined as all the blocks between the source, storage and load, plus the power conditioning equipment required for the source, storage and load. The EPS mass of a wide range of spacecraft is then classified as source, storage or PMAD and tabulated in a database. The intent of the database is to serve as a reference source for PMAD masses of existing and in-design spacecraft. The PMAD masses in the database range from 40 kg/kW to 183 kg/kW across the spacecraft systems studied. Factors influencing the power system mass are identified. These include the total spacecraft power requirements, total amount of load capacity and physical size of the spacecraft. It is found that a new utility class of power systems, represented by Space Station Freedom, is evolving.

Kenny, Barbara H.↗