Electric Machine Technology Symposium (EMTS) 2004
The Technical and Economic Challenges of the All Electric Force

Adam's Mark Hotel, Philadelphia, PA
January 27-29, 2004

Technical Papers Abstracts
NOTE: Titles, authors, and order of presentation may not match what was listed in the event agenda on this web site. The Proceedings cannot be changed once submitted to the printer. The posted agenda is updated as necessary until the event is over.

High Power Density Permanent Magnet Generators
Jason Pepi and Peter Mongeau

The size and weight of electric drive components are primary considerations in their successful integration into various Naval platforms. To date practically all Naval generators are air-cooled 50/60 Hz type machines that are military derivatives of commercial utility-based generators. As such the size and weight of such machines is quite daunting and ultimately can limit their incorporation in many platforms. The key metric of these machines is ~500W/kg and represents a mature technology. Modern advances in alternator design, thermal management and permanent magnet materials can offer substantial improvements in machine power density. Such machines are typified by permanent magnet field excitation; high frequency output, liquid control and brushless DC drive control. Power densities in excess of 1500 W/kg are now possible without the use of advanced composite materials or cryogenic cooling.

Design and Development of a Two Megawatt, High Speed Permanent Magnet Alternator for Shipboard Application
Co Huynh, Larry Hawkins, Ali Farahani, and Patrick McMullen

Conventional gas turbine generator sets consist of a high speed turbine coupled to a low speed alternator through a speed reduction gearbox. This is required to maintain the alternator output frequency at 50Hz or 60Hz, as output frequency is directly proportional to speed. Since power is also directly proportional to speed, the conventional system is bulky and possesses a very large footprint. The advent of solid-state inverters with their unique ability to efficiently and cost effectively change the alternator output frequency has made it possible to eliminate the need to link the alternator speed to the required 50/60 Hz output frequency. This output can be produced with a high-speed alternator, eliminating the need for a gearbox and greatly reducing the size, complexity, and weight of the machine by trading speed for torque. A direct drive system in which an alternator is coupled directly to a gas turbine is much more compact and highly efficient and requires much less maintenance. In this paper we will review the design and development of a high-speed permanent magnet alternator in an advanced cycle gas turbine system for shipboard applications. In addition to the alternator's design features, we will discuss design considerations including electromagnetic design, thermal design and structural design of high speed electrical machines, and review the alternator development including risk mitigation.

A Fault Resilient IPM Motor Drive for Wide Speed Range Operation
Leila Parsa and Hamid A. Toliyat

Interior permanent magnet motors are superior to surface mount permanent magnet motors due to some of their inherent characteristics such as higher torque density. These motors enjoy an extended flux weakening region because of their reluctance torque and ruggedness of the rotor which is an important factor in high speed applications. The above mentioned advantages of the IPM motor depend on the saliency ratio of the motor. In order to obtain high performance motor drives, modern control strategies like field oriented control should be employed. These techniques are inherently dependent on the proper operation of measurement devices, or feedback sensors (current sensors, position sensor or even voltage sensors). In this paper, in order to guarantee a reliable drive, a fault resilient system with soft sensors and automatic controller reconfiguration is designed. These soft sensors substitute the actual sensors in case of sensor failure such that the motor continues operating safely over the whole speed range. Theoretical and experimental results will be presented to validate the proper operation of the proposed back up system.

New Excitation Methods for Direct Drive DC Brushless Motors with Complex Electromagnetic Core Designs
Z. Soghomonian, Ph.D., Z. Rahman, Ph.D., K. Matin, Ph.D.

In direct drive DC brushless motor applications, the main incentive is to increase the torque and power density of the machine design by improving the architectural configuration of the stator and rotor constituents. This normally requires careful consideration in the design of the magnetic circuit topologies, which promotes significant weight reduction in the magnetic mass as well as improvement in the form factor of the magnetic design. Such weight reduction is of paramount importance in minimizing the inertia and unsprung mass in in-wheel hub motors.

Significant performance improvements in motor characteristics are seldom achieved completely with the use of conventional, laminated electrical steels. This is because there are classical limitations as to how much the form factor can be improved to optimize the winding factor and to reduce the bulk of the magnetic mass required for generating the desired torque and power output with the intended cooling.

In most designs, the limitations in 3d isotropic properties of the lamination steels are compounded by the limited freedom in 3d shaping of the lamination stacks. It is therefore difficult to truly optimize the critical path of the magnetic constituents in the motor architectures. Furthermore, there are the classical issues concerning interlaminar eddy, hysteresis and excess eddy current losses, which stem from normal and planar flux distributions in complex magnetic structures of the motors.

A new range of permanent magnet DC brushless motors have been developed for in-wheel and near-wheel propulsion applications, which have the potential of improving the torque-to-weight ratio to 20 Nm/kg. The most important factors in inverted (direct drive) DC brushless motors are manufacturing cost, motor package size, adequate thermal management, lower un-sprung masses and active weight, stator form factor as well as, simplification and modularization of the design for cost effective manufacturing, servicing and reproducibility.

These objectives are met, in part, by careful weight reduction in the active mass of the motor with the use of Soft Magnetic Composite (SMC) materials and different excitation configurations. In these new designs the machines have segmented magnetic stator design [1, 2] that eliminates the mutual induction among different phases, thus allowing flexibility in field weakening controls. Due to the changes introduced in the design of the magnetic circuit of the motors, unique electromagnetic cores are developed that improve the form factor, minimize the active mass and core losses of the motor whilst maintaining the desired motor performance characteristics at the operating frequencies and induction. Different excitation configurations are discussed which complement the improvements made in the form factor of the magnetic constituents. This paper discusses the on-going work at WaveCrest on its segmented magnetic motor topology, which is further complimented with proprietary inverter power electronics and control algorithms. Some results are presented in this paper, which are supported with typical torque and speed plots. The control algorithm used is a subject of a different paper presented at this symposium under the title "Prephase d-q Model for Multiphase PM Motor with Segmented Magnetic Paths".

Effects of Discontinuities on Radiated Noise of Submerged Motors
Timothy E. McDevitt, Robert L. Campbell, and David M. Jenkins

Circumferentially uniform radial magnetic stresses (n=0 stresses) have the potential to cause efficient sound radiation from electric machinery. These stress waves can appear in the magnetic stress spectrum at a variety of frequencies due to various m.m.f. and permeance harmonics. By finite element and boundary element techniques, we investigate the nature of sound radiation caused by these stresses; how it is influenced by the acoustic medium and how the motor supports can come into play. Higher order vibration response harmonics introduced by the supports play a significant acoustic role in air, but a less significant role in water due to radiation damping and higher wavenumber radiation efficiency drops.

Development of Electric Propulsion Motors with Integrated Power Electronics
E. Schroeder, M. A. Pichot, A. Ouroua, M. M. Flynn, J. H. Beno

The effective integration of electric power in future naval ships requires the development of technologies that allow for volume and mass reduction of critical components. The University of Texas at Austin Center for Electromechanics is studying the potential for volume and mass reduction through the integration of power electronics into an electric propulsion motor. Two conceptual designs of a motor with integrated power electronics are presented. Integration of power electronics into the motor frame offers space saving advantages, allowing the motor and power electronics to share the same housing and cooling system. Accordingly, significant mass and volume reductions are possible in the power electronics housing and cooling auxiliaries.

Hybrid Load Commutated Inverter-Based Induction Motor Drive for Commercial and Military Ship Propulsions
Sangshin Kwak and Hamid A. Toliyat

Load commutated inverter (LCI)-based induction motor drives are important for high power applications such as commercial and military ships propulsions due to their suitability for high power application, robust and simple structure. A novel, hybrid solution employing a combination of a load-commutated inverter and a voltage-source inverter is proposed for the induction motor drives. By avoiding the use of output capacitors and a forced dc-commutation circuit, this solution can eliminate all disadvantages related to these circuits in the conventional LCI based induction motor drives. In addition, improved quality of output current waveforms and faster dynamic response can be achieved. The proposed hybrid scheme features the following tasks: 1) the safe commutation angle for the LCI, controlled by the voltage source inverter (VSI) in all speed region of the induction motor and 2) a dc-link current control loop to ensure minimum VSI rating and maximum LCI rating. Advantages of the proposed solution over the conventional LCI based induction motor include the followings: 1) sinusoidal motor phase current and voltage based on the instantaneous motor speed control; 2) fast dynamic response by the VSI operation; 3) elimination of motor circuit resonance and motor torque pulsation. The feasibility of the proposed hybrid circuit for the high power drive system is verified by computer simulation for a 500 hp induction motor. Experimental results to support the use of the proposed system are also included for a 1 hp induction motor laboratory setup.

An Evaluation of High Torque Density Electric Motor Topologies and their Application for Ship Propulsion
B. W. Eckels and R. M. Calfo

The desire for highly torque dense Naval propulsion motors has resulted in advances in the various competing motor architectures. Designs for three of the AC synchronous motor types are shown to have the capability to provide weight based torque densities in the range of 10 to 20 ft-lb/lb. The high torque density motors studied include an embedded permanent magnet design and two wound field designs, one with high temperature superconducting field windings, and one with conventional windings. For each of these motors, an optimum diameter, or diameter for which the total motor weight is minimized is shown to exist. The optimal diameter differs markedly between these three machines suggesting that for high torque density applications, the available packaging envelope may preferentially advocate a particular motor topology. Other factors such as efficiency, acoustic performance, reliability and survivability further define the most appropriate motor configuration for the particular mission.

Submarine Electric Actuation Systems … Present and Future Concepts
Steve Weinstein

Electric actuation is one of the major enabling technologies for achieving the all-electric submarine. A current U.S. Navy Research and Development effort involves the selection and replacement of submarine hydraulic actuation systems with electric actuation systems. Electric actuation technology offers an opportunity to remove a large percentage of maintenance intensive hydraulic system piping and components. Performance requirements for selected actuation system applications are being defined and the procurement of prototype systems are planned for testing. A Small Business Innovation Research topic is currently seeking a technology concept that replaces the hydraulic hoist system of the Universal Modular Mast with an electric direct-drive system. Other electric actuation technology developments underway include scaled testing of direct electromagnetic actuator prototypes and advanced control surface actuation technology using Shape Memory Alloy materials. These new technologies have the potential to improve submarine maneuvering performance and provide substantial lift enhancement and torque reduction for local control surface actuation. This paper addresses the potential applications and performance capability payoffs of electric actuation technologies. Insight will be given into how these technologies are currently being evaluated, demonstrated, and planned for future insertion on submarines.

On the Linear Synchronous/Induction Motor Choice for Electromagnetic Aircraft Launch
James L. Kirtley Jr.

This paper is a discussion of the choice between linear synchronous motors using permanent magnets and linear induction machines for electromagnetic aircraft launch. This is an unusual electric machine application as it requires very large force densities over relatively short times. It is shown here that, while high force densities can be achieved with permanent magnets, induction machines can also achieve the requisite force densities. Induction machines for this purpose would have lighter shuttles and lower electrical frequencies: possible advantages.

Shipboard Actuators: Conversion from Hydraulic to Electric
Donald Locher, Duane Hanselman, and Ronald LaFleur

This paper considers the use of electric actuators in shipboard applications that have traditionally been implemented using hydraulic actuators. Before this transition to electric actuators can occur, the strengths and weaknesses of electric actuators must be identified. In particular, the type of electrical actuator, the presence and type of transmission or mechanical linkage required, as well as the power electronics and power input requirements must be chosen. By addressing these issues, this paper provides valuable information that facilitates the conversion of actuators from hydraulic to electric in naval vessels.

Measurement of Stability Margins in Single Phase and Polyphase Switchmode Power Systems - A Tutorial Introduction
Michael L. Williams, P.E.

Switchmode power converters may cause the power system to become unstable because of negative resistance that exists at their power input terminals. Instability can result in erratic system operation, component overstress, and catastrophic failure. Methods of stability margin measurement in DC systems are well established in the industry. For AC systems, the methods have been obscure. Existence of specification and test methods does not fulfill the programmatic needs for implementation. There is a need for acceptance of the methodology by the development community. Such acceptance is greatly improved if the methods involved can be understood to an extent that provides a degree of comfort with the process. The intent of this tutorial is to present the methods of AC stability margin measurement in steps that are easy to grasp.

An Optimal Control Technique For Compensation of Harmonic Base Motion in Magnetic Bearing Rotors
Steven Marx and C. Nataraj

A rotating system, supported on magnetic bearings, is considered. The magnetic bearings are modeled by accurate nonlinear mathematical models, and the rotor is modeled by a single degree of freedom. The support of the system is assumed to be subject to a harmonic disturbing motion. A new control scheme is proposed consisting of a combination of a conventional magnetic bearing controller along with an optimal harmonic amplitude-based controller. Numerical simulations show that the vibration can be substantially reduced with the new controller system.

High Power Multi-Channel Current Drive for Inductive Loads
Ross Bird, Brian Shea, William Knoll, Michael Goehrig, and John Staron

The goal of the Linear Motor Technology in the Vertical Plane project was to provide a full solution design of a compact and lightweight system capable of replacing heavy maintenance and power intensive hydraulic systems for ship deck operations. The system introduces advances in switching topologies, components, and subsystem designs for inductive loads as to minimize the weight and power costs. During the program, developments were made in the thermal management system, POLYBRIDGE™ inverter, fault free modulator, fiber optic negative offset gate drive, PFC bi-directional converter, and DSP control platform. The developments provided the ability to achieve the goals set forth by the application. The solution contained three focus areas: 1) the thermal management solution was addressed by component package selection, switching architecture and heatsink design 2) the power inverter system was designed with noise immunity and isolation as the main concerns and 3) the DSP control platform was engineered to allow flexibility and versatility in the drive configuration and capabilities. A combination of these individual elements is seen in the solution developed specifically for driving large inductive loads at high power levels. The technology is a modular scaleable system that facilitates the future growth of the application.

Linear Synchronous Motor Applications for Advanced Navy Elevators
Piet VanDine and Pete Rinaldi

General Dynamics Armament and Technical Products (GDATP) and General Dynamics Electric Boat (GDEB) have developed a complete conceptual design employing linear synchronous motor (LSM) technology for an Advanced Elevator (AE) system. The LSM-AE system conceptual design is focused upon upgrading the legacy weapons elevator systems currently in use aboard U.S. Navy aircraft carriers to ropeless, all-electric systems. This paper will explain how linear motor technology eliminates a number of deficiencies in legacy elevator systems while providing significant capability enhancement in areas of throughput, survivability, life cycle cost, manpower reduction, reliability, operational flexibility, and maintainability.

An Advanced Linear Motor System for Electromagnetic Launch: Development and Opportunities
Lt Cdr Matt Bolton, RN, Helen Robertson, and Lt Wayne Ubhi, RN

The requirement for launching aircraft, in the future, from electric powered aircraft carriers has led to an interest in electro-magnetic launch systems to replace the steam catapult. This paper will discuss the successful development of an advanced linear motor launching system, originally considered as an option for the UK's future carrier programme. The Electro Magnetic CATapult system (EMCAT) will be explained along with descriptions of the major components. The results of some of the hardware testing will be revealed and the implications of these results on a full system will be discussed. In addition the advantages over a steam catapult, system maturity, impact upon ship design and potential future application for the technology are also discussed.

Transformation of Submarine Towed Array Handling Systems To Electric Drive
Joseph P. Liguore, Edward K. Robinson, and Curt E. Schwarz

This paper describes the all-electric towed array handling system being installed on Virginia class submarines.

The Effect of Design Tolerances on Far Field of Permanent Magnet Motor
O-Mun Kwon, Sheppard J. Salon, and M.V.K. Chari

Exterior magnetic fields computation of permanent magnet synchronous motors are of importance in naval applications with respect to electromagnetic interference and detection. For shipboard applications far field effects due to currents in the stator windings, induced magnetic field in the iron parts and permanent magnets in the rotating members of motors are of significance and their accurate evaluation is vital to providing remedial measures. In this paper, the effects due to all above are analyzed using a scalar potential method.

Physical Machines Models for Integrated Motor Drive Applications
O. A. Mohammed, S. Liu, Z. Liu, L. Petersen, J. Muench, and R. McConnell

Several physical models of electric machines are being developed for utilization in integrated motor drive applications instead of the customary dq models. In this paper we report on two models implemented in Simulink along with various PEBB topologies; the phase variable model and the full finite element (FE) model. In the phase variable model, the inductances used to construct the equivalent circuit are calculated from the FE solution, which includes slotting effects, nonlinearity and other geometrical features. The full finite element model is directly implemented and solved in real time along with the rest of the motor drive. These modeling techniques allow the user to include all harmonic components, geometrical features and circuit topologies as well as operational variations at the same time. This enable the user to include all effects neglected by using dq models and allow discovery of new phenomena when evaluating plug and play PEBB devices.

High Torque Density Propulsion Motors
Peter Mongeau

The size and weight of electric drive components are primary considerations in their successful integration into various Naval platforms. Direct drive propulsion motors are of particular importance due to their requirement of developing full power at low shaft speed. As such, their torque density (ft-lbs of motor torque developed per lb of motor mass) is the key defining metric. Torque density projections of existing and future technology machines require thorough understanding of the constituent mass elements that comprise an electrical machine and their specific scaling relationships. Such models can be used to compare machine performance across a wide range of objective torques and technologies. Liquid-cooled permanent magnet motors typify current state of the art propulsion motors. The torque density of such motors at ~ 2Mftlbs is roughly 8 ft-lbs/lb which represents a twofold increase over the prior generation of air-cooled induction motors at ~ 4 ft-lbs/lb. The next generation of propulsion motors technology, advanced PM motors and high temperature superconductivity motors, are targeting >16 ft-lbs/lb as achievable goals.

Development of a Comprehensive Fuel Cell Model for Marine Applications
B. Carroll and T. Kiehne

As technological advancements continue to produce smaller devices with increased power density, the need for design-stage thermal analysis has become increasingly important. In response to a wide array of thermal management issues for future all electric warships, interdisciplinary models are under development to address shortcomings of system-level simulation tools for marine-based power systems, including pulsed weapons and sensors. Because of its inherent complexity, the fuel cell system is a viable entry point for this class of simulation as a step along the path to more comprehensive dynamic models. This paper describes the on-going development of a first principle based model of the thermodynamics, electrochemistry, and electrical irreversibilities of fuel cells. The model tracks the transient temperature response, chemical specie exhaust gas evolution, electrical characteristics, and fuel reformation process. Operating parameters addressed in this paper include system pressure and temperature, reactant concentration, current density, and reformation steam to fuel ratio.

Calculation of the Rotor Losses in a Canned Solid Rotor Induction Motor with a One Slot Model
Lale T. ERGENE and Sheppard J. SALON

This paper analyzes a one-slot model of a specific type of induction motor, a canned induction motor. These motors are used in naval applications. This machine has thin, cylindrical, non-magnetic cans inserted in the air gap of the motor to prevent the liquid from entering the stator and rotor and damaging the windings. The reason for creating the one-slot model of the solid rotor induction motor is not only to simplify the whole model and reduce the computational time but also to predict the extra losses due to the high frequency. These losses are mainly due to the rotor tooth pulsation under the stationary stator slots and paper shows how to compute these rotor parts' losses with the one-slot model. The results are compared with the full transient model of the induction machine.

5MW High Temperature Superconductor Ship Propulsion Motor Design and Test Results
P. W. Eckels and G. Snitchler

American Superconductor has designed, built, tested and delivered to the U.S. Navy's Office of Naval Research (ONR) a 5MW, 230-RPM, 6-pole high temperature superconductor (HTS) ship propulsion motor. The motor uses an air core armature winding and first generation HTS wire (BSCCO-2223) field winding. The goal of the motor development project was to validate the technologies required to design and build larger HTS ship propulsion motors, as well as to develop a motor production process that streamlines development time and minimizes cost. A commercial variable frequency drive is used to power the motor. The HTS field winding is cooled with G-M coolers with gaseous helium as the cooling medium in a closed cycle. The armature is cooled by Midel®. The motor was delivered to the U.S. Navy in July 2003 and met or exceeded requirements in operation (up to the facility's testing limit of 2.5MW). The motor demonstrated both full torque and full speed operation in separate tests.

High Temperature Superconducting Motor Power Density Improvements
Christopher T. Farr and Raymond M. Calfo

The use of high temperature superconducting (HTS) wire technology enables magnetic shear stress improvements in rotating machinery as high current densities can be achieved. The use of HTS wire, however, requires a large effective magnetic gap due to the use of full air-gap style stator windings as well as thermal insulation and electro-magnetic shielding to maintain HTS rotor coil operating temperatures within required limits. Due to these large magnetic gaps, HTS machines require large pole pitches to maximize the flux that links stator coils. Large pole pitches result in low pole numbers, which increase stator core and support structure weight. The use of a partial air-gap stator winding (CW-EMD patent pending) in an HTS motor effectively reduces the magnetic gap, which results in increased flux linkage with stator conductors. Reductions in the effective magnetic gap allow for the selection of smaller pole pitches and thus weight savings.

Superconductor Generators Promise Higher Reliability and Ease of Operation
Swarn S. Kalsi

A simple replacement of conventional copper field winding with a superconducting field winding yields a generator with superior performance, higher reliability and easier operation. Synchronous machines with superconducting field windings have been in development since the mid-sixties. Initially field windings in these devices employed low temperature superconductors and were not economically attractive due to the cost and complexity of the cooling system. The emergence of high temperature superconductors coupled with much simpler, less costly cooling systems has provided new impetus to the development of such machines. These machines employ high temperature superconducting (HTS) field windings and are characterized by low synchronous reactance, which delivers better system stability. Since these field windings always operate at constant cryogenic temperatures, they do not experience fatigue due to repeated expansion and contraction in response to field current changes caused by load changes. This feature makes these machines suitable for both base load and peak load applications. Machine life is limited only by the conventional stator winding. Compared with conventional generators, HTS generators are lower cost, more compact, lighter weight, more efficient and quieter. They have also higher critical clearing time and much lower total harmonic distortion. These features were successfully demonstrated in a 5000 hp, 1800-rpm motor in 2001. Existing rotating machines can also benefit from this new technology, simply by replacing their conventional rotors with HTS rotors.

Power Conversion System Benefits of Reduced Temperature Operation
R.J. Thome, E. Bowles, M. J. Hennessy, E. K. Mueller, M. J. Gouge, and P. Lopez

The study of the benefits of reduced-temperature operation in power conversion systems has focused on three systems: a Homopolar Motor Ship Electric Drive, an Integrated Power System (IPS), and an Electromagnetic Aircraft Launch System (EMALS). The general approach was to: (1) define a baseline, 300-K system configuration for each case; (2) perform a conceptual design of ~80 K components to allow weight, size, and operational attributes of the system components to be determined; (3) assess the system impact and potential benefits of 80 K operation; and (4) carry out an R&D needs assessment to identify areas for high impact R&D. It was found that the use of selected cryo-cooled components in place of conventional designs would lead to substantial savings in weight, volume and energy losses for the Homopolar Motor Power Conversion System and the Integrated Power System modules, but no significant advantage for the low duty cycle EMALS Power Conversion System. The largest savings are of order 2 for weight and volume and a factor of 5 for losses for the steady-state systems, including the cryogenic cooling system. Our R&D assessment of the high impact items identified areas that should be pursued to realize the maximum benefit.

Double-Side Double-Gate IGBT Fabricated by Wafer Bonding
F.J. Kub, K.D. Hobart, J.M. Neilson, and P.R. Waind

This paper discusses the experimental results for high voltage double-side IGBT (DIGBT) fabricated by direct wafer bonding high voltage IGBT wafers backside-to-backside. The backside gate of the DIGBT operates as an active anode short and controls the injection of excess minority carrier charge into the thick base region prior to turn-off. The turn-off loss is reduced by approximately a factor of three for a DIGBT with and a factor of nine for a DIGBT without an n-buffer. The DIGBT when used as a free wheeling diode achieves approximately a 50% reduction in reverse recovery peak current and an 80% reduction in recovery charge.

Reconfiguration of Shipboard Radial Power System using Intelligent Agents
Li-Hsiang Sun and David A. Cartes

We describe a multi-agent system currently under development in Center for Advanced Power Systems in Florida State University. The problem we are trying to solve is to reconfigure the shipboard power system without human intervention and without centralized scheduling and planning. Our solution is to use an agent to represent and exert high-level control on each critical system component. By summarizing the power budget and cost, the resource can be reserved, de-allocated and redistributed without the scheduling of a central entity. The agent in the system only communicates with its immediate neighbor, reducing the dependency between the reconfiguration algorithm and system topology. The behaviors for this agent network are described in detail. The deadlock avoidance and adequacy of the solution are also discussed.

Modulation Algorithms for Neutral Point Clamped Converters
Ashish Bendre, Slobodan Krstic, James Vander Meer, and Giri Venkataramanan

Abstract-Three level diode clamped converters are seeing increased application in industrial drive systems as they allow the use of lower voltage devices in higher voltage applications, provide reduced output voltage THD due to extra switching levels and can develop lower common mode voltage than equivalent two level converters. However, these converters require active balancing mechanisms to maintain neutral point voltage balance and further exhibit significant low frequency harmonics in the neutral point current. Various space vector strategies that eliminate the common mode voltage, provide low THD output voltage or eliminate the neutral point current ripple have been proposed. However, each of these strategies targets one aspect of the performance of the converter while degrading it in other areas. In this paper three modulation methods for three level converters are compared - nearest three vector, radial state and zero common mode using metrics that clearly elucidate the tradeoffs involved with each modulation scheme. Analysis, simulation and hardware results are presented for the three modulation methods.

Circuit Design Optimization for High Power Density Electronic Assembly
Dr. Yuri Khersonsky and Chi Mak,

Traditionally power density of power electronic devices is determined by the same rule as in rotating machinery. It based on load current, and 10% overload for 10 min. To compensate for power semiconductors relatively small thermo mass, the applications manuals recommend rating of the semiconductor device around 150% of the full load current. However in most applications, the semiconductor rating should be much higher to envisage the conditions such as unbalanced current sharing between multiple paralleling semiconductors, withstanding of short circuit current and thermal stress caused by the short circuit current interruption. Employing higher rating semiconductors not only increases the cost, but also increases the volume of the assembly, thus reduces power density. Real increase of the power density could be achieved by dedicated force cooling, current limiting control system and novel devices such as inter-phase transformer to balance transient current sharing between semiconductors and voltage suppression assembly to absorb the switching transient energy. These approaches have been demonstrated in Power Paragon's Power Systems Group's (PSG) products developed for US Navy.

The Development and Testing of Integrated Fight-Through Power Modules for the U.S. Navy Fleet
James Zgliczynski, Richard Street, James Munro, James McCoy, Neil Hiller, and Jignas Cherry

As part of the U.S. Naval Sea Systems Command (NAVSEA) program to develop integrated power system (IPS) advanced power conversion modules for the Integrated Fight-Through Power (IFTP) concept, a team of high technology companies, led by General Atomics, has successfully manufactured, tested and delivered a suite of megawatt class power conversion modules to U.S. Naval Surface Warfare Center, IFTP land Based Test Site, Carderock Division (NSWCCD) - Ship Systems Engineering Station in Philadelphia. The zone of power conversion modules, or PCMs, consists of a 2000 kW 4160 Vac to 1000 Vdc rectifier, two 750 kW 1000 Vdc to 800 Vdc converters, and a 500 kW 800 Vdc to 450 Vac three-phase inverter. The PCMs were successfully tested at General Atomics and at NSWCCD both individually and in the integrated IFTP configuration. High levels of power quality were demonstrated by all the PCMs even when powered by a propulsion bus with very high total harmonic distortion. Testing also demonstrated the computer controlled power flow management and the fault isolation and reconfiguration features that support the IFTP concept to respond to battle damage. In a follow-on phase of this development effort, the General Atomics team will design, manufacture and test IFTP power conversion modules for at-sea testing on board the British research vessel R.V. TRITON.

Per-Phase D-Q Model for Multiphase PM Motors with Segmented Magnetic Paths
Guohui Yuan, PhD, Min Fung Shiei, MSEE, and Matthew Feemster, PhD

A per-phase d-q model has been discussed for a unique design of multiphase permanent magnet synchronous motors (PMSM). The uniqueness lies in the fact that the magnetic path for each phase is isolated from those of its neighboring phases. The physical segmentation of the electromagnetic cores on the stator not only minimizes the active mass and reduces core losses, but also presents a simpler motor control structure. Two optimization objectives are thus formulated based on the per-phase d-q model. The first is to maximize the total torque output of the motor for given a current and voltage rating. The second is to maximize torque-per-ampere and therefore motor efficiency for a given torque request. Some highlights of on-going theoretical and experimental studies presented.

Electric Propulsion Systems: Past, Present and Future Applications for the Navval and Commercial Market
Jonathan D. Sauer and Paul E. Thompson

This paper will embark on a voyage through time, highlighting electric propulsion systems in both naval and commercial markets. Several examples will highlight the propulsion converter and motor technology implemented in a variety of vessels. Future propulsion system technology will also be discussed.

Integrated Electrical Power Node Delivery System for Enhanced Ship Service Load Survivability and Power Quality
Cliff Allen, John Barber, and John Ykema

This paper presents another approach for a highly reliable ship serv-ice power delivery system. The focus is to provide continuously available qual-ity power to the maximum number of loads at minimum cost. The system em-ploys two key elements: the Power Node Control Center (PNCC) and the Power Node Switching Center (PNSC), both of which are described. The benefits of this system are given under the headings Load Survivability, Load Power Qual-ity, System Control, and Affordability. Product availability is anticipated in 2005/2006.

The Need to Ensure an Uninterruptible Supply of Computer Grade, Conditioned and Regulated Single Phase (1Ph) 120V Power for Equipment and Systems Critical/Vital/Essential to the Safety, Warfighting Capability, and Survivability of the Ship
Mr. Michael J. DiTaranto, Mr. William W. Simunek, and Capt. John Strachan, USNR (Ret)

The accelerating proliferation shipboard of increasingly sophisticated, power quality sensitive, single phase (1Ph) electronic equipment and systems in support of burgeoning Mission Critical/Vital/Essential (MCVE) C4ISR and NetCentric Warfare requirements, coupled with ongoing plans to reduce future manning levels through increased use of automation, and the expanded use of Commercial-Off-The Shelf (COTS) technology, is driving the increasing use of Uninterrruptible Power Supply (UPS) equipment. To support these systems, this equipment must be both state-of-the-art and proven/qualified for use in the severe electrical and physical environment of a naval combatant. This paper reviews background and problems experienced to date, discusses actions taken, and proposes additional steps that need to be taken to ensure that future 1Ph-120V UPS supporting MCVE equipment and systems are fully tested and qualified for use aboard naval combatants.

Physical Model Based, Iterator Driven Integrated Design, Control and Information Management
LCDR Kevin Russell, USCG, Dr. Robert Broadwater, and John Rapp

The modeling technique described in this paper was originally developed to perform automated load flow, reliability design and reconfiguration analysis for very large electric utility distribution systems. It is built around the use of object based system drawings and iterator driven generic trace algorithms that directly use the physical structure of the system to simplify analysis and coordinate data management and processing between multiple analysis applications, and legacy monitoring and configuration management systems. The paper discusses the basic system architecture and analysis concepts used by the approach, current power utility use and potential application to shipboard systems. The approach, referred to as reference modeling in the paper, could be applied to any system, structure or process that can be described as a network of interrelated objects. Research is currently underway to develop contingency model based real-time reconfiguration control and supervisory monitoring for electric utility distribution and transmission systems using web and multi-processor based approaches. Possible shipboard applications include integrated survivability design and control analysis across multiple systems, and top-level hierarchical control for intelligent agent based systems. The concepts from this approach could also be applied to high-rise buildings, offshore oil platforms and industrial facilities.

Multi-Domain Motor/Drive Simulation
Dr. Mike Mekhiche, Andrew Keefe, Rob Cuzner, Craig Goshaw and Thi Nguyen

Modeling modern electric drive systems involves an intimate understanding of the interactions between the motor, drive and controls. Earlier simulation efforts using reduced order behavioral models were adequate for representing overall system performance. Circuit simulation tools such as Pspice are perfectly adequate for time based simulation of analog circuitry but are cumbersome for incorporating digital controls. Simulink is a very powerful control oriented modeling tool but does not capture true circuit response. A new class of multi-domain simulation tools such as Simplorer and Saber are emerging that are equally conversant in digital controls and circuit response. Simplorer, in particular, has the capability to serve as an open interface simulation backbone that can couple existing models in Spice, Simulink, VHDL, MathCAD, etc. in a common full fidelity simulation environment. This tool also has the capability to couple hybrid circuit-control models with fully detailed electromagnetic FEA based motor models providing a unique level of integrated modeling. Such tools are invaluable for analyzing tightly coupled interaction effects such as the motor EMI effects of device switching in response to certain control algorithms, and system faults simulation.

Large-Scale Simulation of Naval Power Systems for Design Optimization
S. Woodruff

The use of large-scale simulations to accurately predict the behavior of the complex, closely coupled power systems characteristic of the all-electric ship is described and the application of such simulations to the systematic optimization of power systems and control systems is discussed. Simulations of a two-generator, two-motor system with PWM drives are coupled with a gradient-based line-search optimization strategy to determine the gains on a motor controller and on a simple ship-wide control system to minimize both motor speed error and generator speed error. The same search strategy is employed with simulations of a series PWM converter configuration to permit determination of an interconverter filter that gives the most accurate reproduction of a target waveform at the filter output. The results of even these relatively simple test cases show clearly the necessity of large-scale simulations for understanding and designing electric-ship power systems and the potential utility of optimization techniques in concert with the large-scale simulations to enhance the performance of electric ships.

Inverse Magnetostriction Effects on Electrical Machinery
O.A. Mohammed, S. Liu, S. Ganu, T. Calvert, L. Petersen, J. Muench, and R. McConnell

The Inverse Magnetostriction Effect (IME) is included in the magnetoelastic coupled FE analysis. In magnetic field equation, the effects of the stress on the ferromagnetic permeability are considered while forming the magnetic stiffness matrix. In mechanical field equation, the force due to IME origin is added to the magnetic forces, which is evaluated by Virtual work principle. It turns out that there are forces existing inside the ferromagnetic material if the IME is taken into account. A PM surface mounted motor is used for the implementation. The magnetic forces acting on the stator iron and the corresponding deformations with and without IME are compared.

Development of Advanced Dielectrics for High Energy Density Capacitors
Ming-Jen Pan, Barry Bender, Roy Rayne, and Michael Lanagan

The first part of this paper describes the research strategy at the U.S. Naval Research Laboratory on the development of advanced capacitor materials, with an emphasis on ceramic-based dielectrics. We laid out a systematic approach to utilize ceramic dielectrics for specific applications and/or to engineer the construction of capacitors/dielectrics such that high volume production is possible. The second half of the paper illustrates one of the material solutions-ferroelectric glass-ceramics. By starting with a porosity-free glass and then precipitating ferroelectric particles within the glass, the dielectric breakdown strength was several time higher than that of conventional ceramics while maintaining relatively high dielectric constant. As a result, the projected energy density is in the range of 7-8 joules/cc with ample room for further improvement.

Electrochemical Capacitor Energy Storage Systems for Submarine Electric Actuation Systems
Stephen A. Merryman

Electrical actuator systems are being pursued as alternatives to hydraulic systems to reduce maintenance time, weight and costs while increasing system reliability. Additionally, safety and environmental hazards associated with the hydraulic fluids can be eliminated. Electrochemical capacitor (EC) technology is being pursued heavily for these electrical actuation applications. Electrochemical capacitors are a class of devices that have emerged in recent years that exhibit some of the attributes of both batteries and traditional capacitors. They are intermediate between classical capacitors and batteries in terms of both energy storage density and power density. Electrochemical capacitors have the highest demonstrated energy density for capacitive energy storage, have power densities much greater than most battery technologies, are capable of greater than one million charge-discharge cycles, can be charged at extremely high rates, and exhibit non-explosive failure modes. In this research effort, electrochemical capacitors are being considered as part of the power system for electric actuation applications aboard submarines. Several different electrochemical capacitor technologies are being investigated as potential candidates for powering submarine electric actuation systems and will be included in the study to size power sources for these applications. Electrochemical capacitor banks have been tested in configurations that simulate the power profile required for the suite of electrical actuators aboard a submarine. Based upon these tests and the results of system modeling, preliminary design concepts for capacitor power systems that offer high energy and power densities and low losses are being developed to drive the suite of electric actuators aboard submarines and are presented in this paper.

A Fault-Tolerant Multi-Phase Permanent Magnet Motor Drive for Propulsion Applications
Leila Parsa and Hamid A. Toliyat

In this paper, a new five-phase brushless permanent magnet motor is proposed. The proposed motor has concentrated windings such that the produced back-EMF is almost trapezoidal. The motor is supplied with the combined sinusoidal plus third harmonic of currents. For presenting the superior performance of the proposed five-phase motor, its three and five-phase counterparts are also analyzed. The resilient current control of the five-phase PM motor under asymmetrical fault conditions is also presented. This kind of control scheme ensures that the five-phase PM motor operates continuously and steadily without additional hardware connections in case of loss of up to two phases. In applications such as naval applications where fault tolerance and high reliability are required the proposed resilient control scheme is of paramount importance.

Recent Developments in Current-Based Induction Motor Condition Monitoring
Thomas G. Habetler, Ronald G. Harley, Rangarajan M. Tallam, Jason Stack, and Xianghui Huang

This paper presents an overview of work done in both protection and condition monitoring of electric machines using only the quantities typically available in a motor control center; the terminal voltage and current. An overview of rotor fault prediction and stator winding protection methods developed at Georgia Tech for complete motor monitoring is presented in this paper. The paper will look at methods for BOTH motors directly connected to the mains supply, and motors supplied by variable speed drives.

Diesel Engine Modeling for Electrical Step Load Changes
Dr. Samuel Doughty, Dr. Mark Roberts, and Ms. Margaret Mericle

Step load changes have long been used to evaluated frequency deviation and settling time for engine generator sets in all applications, including shipboard. In recent years, it has become possible and desirable to simulate this response at the design phase of the system. For this purpose, mathematical models are required for the engine, generator, governor, voltage regulator, and perhaps other system components as well. The correct development of engine models has presented some difficulty over a period of years, with various organizations and individuals offering their own versions. This paper will offer a model that is simple, highly faithful to the actual physical system, and easily understood by the user. In regard to engine modeling, there are additional issues regarding the degree to which the engine model should be integrated with the larger system model, and whether the engine model should be dimensional or non-dimensional. These topics are also addressed in the paper.

Investigation of Permanent Magnet Motor for Miniaturization in Ship Propulsion
G. H. Kang, J. Hur, B. K. Lee, and D. W. Yoo

In this paper, the irreversible demagnetization characteristic of permanent magnet (PM) Brushless DC (BLDC) motors according to rotor structures is explained in detail. The instantaneous currents at starting or in lock rotor condition are calculated from current dynamic analysis by coupled electric and magnetic field using Finite Element Method (FEM). The currents are used for the irreversible demagnetization field analysis by FEM. In the irreversible demagnetization analysis, a new FE analysis method is proposed in order to consider the variation of residual flux density in PMs and the magnetic core, simultaneously.

Metal Fiber Electrical Brushes for Existing and Future Generator Systems
D.W. Scherbarth, E.D. Scott, D.T. Hackworth, D. Kuhlmann-Wilsdorf, J.T. Moore, M.S. Bednar, R.B. Nelson, and W.M. Elger

This paper reports on an Office of Naval Research (ONR Code 33X) sponsored, applied research investigation where HiPerCon metal fiber electrical brushes were designed and built for subsequent testing on a Curtiss-Wright pulsed generator that incorporated a K-Monel slip ring collector. The replacement of monolithic carbon brushes with high performance, metal fiber electrical brushes can dramatically reduce or eliminate brush problems on a K-Monel slip ring, significantly improving the operational availability, maintainability and performance of the generator under a wide range of operating conditions.

Advanced Self-Diagnosis Scheme for Multi-Converters in Electric Ship Propulsion Systems
B. K. Lee, J. W. Baek, D. W. Yoo, G. H. Rim

In this paper, a novel and effective diagnosis scheme for pwm converters in electric ship propulsion systems is proposed. In this method, only three-phase input currents are used as estimation data to diagnose switch fault status and with the proper transformation process, these data are transferred into distinct graphical diagrams for easy evaluation. The developed diagnosis scheme will be explained in theoretically and the validity will be verified by the informative simulation and experimental results in detail

Thermal Management for the Electric Warship
Mark Zerby & Kevin King

The projected design features of the All Electric Ship (AES) will generate additional waste heat. The addition of advanced power electronics, advanced radar, advanced defense systems, and weapons systems such as the EM Railgun and the Free Electron Laser in future Naval combatants, may result in heat loads eventually requiring a 700% increase in cooling capacity. Advanced power electronics, high power sensors, and weapons inserted in high-speed naval vehicles require an evolution in cooling technologies and architectures.

New cooling technologies have been studied and identified as candidates to provide cooling for the future Navy. These technologies also require a systems approach to transfer the extremely high heat fluxes to the sea. To determine the impacts of inserting a particular advanced thermal management technology requires an integrated systems approach. A new technology may or may not be effective within existing system architecture. New system architectures may be necessary to fully implement these technologies. Also, there are instances where the new technology is the new system architecture. Using an integrated systems approach accounts for interactions and resulting benefits/ adverse effects. A number of thermal management architectural concepts have been studied for consideration in the AES.

High power sensors and weapons require a systems approach based on the documented emerging cooling requirements to enable effective thermal management on next generation naval vessels. The fundamental payoff for implementing advanced cooling technologies and architectures is the enabling of advanced propulsion technologies and weapons, and the introduction of a new class of non-chemical air conditioning and refrigeration technology to the Navy.

Distributed Heterogeneous Simulation of Naval Integrated Power System
C. E. Lucas, E. A. Walters, J. Jatskevich, O. Wasynczuk, P. T. Lamm, and T. E. Neeves

In this paper, a powerful technique of simulating large-scale dynamical systems is applied to a naval integrated power system. This approach enables the overall system simulation to be formed as the dynamic interconnection of interdependent simulations, each representing a specific electrical, mechanical, hydraulic, and/or thermal component/subsystem. Each simulation may be developed independently using possibly different commercial-off-the-shelf simulation programs thereby allowing the most suitable language or tool to be used based on the design/analysis needs. The simulation paradigm provides a structure that offers a convenient means of implementing simulations utilizing single-, multi-, or parallel-rates integration approaches as well as any combination thereof. Specifically, each component can be simulated using a time-step and integration algorithm that is best suited for that subsystem. The integrated power system is an advanced naval electric power system that includes a zonal dc electric distribution system and an integrated electric generation and propulsion system. The composite system simulation is implemented on a three-computer network of personal computers by interconnecting simulations of the constituent subsystems. In addition to the aforementioned advantages, it is shown that significant improvements in computational speed are achieved using this approach.

Electromagnetic Modeling for Ultra-Fast Actuation
Vincent Leconte, Vincent Mazauric, Olivier Chadebec, and Philippe Wendling

The numerical tools required for the transient modeling of electrical machines are reviewed from an energetic viewpoint. The consistency with the finite element method is given. The impact of these modeling capabilities is stressed on two ultrafast devices, namely the Thomson effect device and the electric railgun. While the choice of 3D current-based formulations consistent with thermodynamics is highlighted in the latter, attention should be paid, in the former, on couplings between magnetic field and (i) electric circuit along with (ii) rigid body motion. Ultimately, further 3D-developments should include both (i) current-based formulations consistent with electric circuit coupling, and (ii) remeshing techniques to take into account general rigid body motion.

PEEC Method for Power Busbar Design
J-P. Gonnet, V. Mazauric, J.-M. Guichon, and P. Wendling

This paper presents the power of the PEEC (Partial Element Equivalent Circuit) method to deal with electrical distribution networks. Because the air regions are not meshed, this method is very efficient for modeling the electromagnetic behavior of busbar systems surrounded by large air volumes-i.e., any power distribution system. Furthermore, this method is shown to be efficient for both high and low frequency problems. Thus, the electromagnetic disturbances caused by wirings are evaluated. This method is not only a modeling method. It also enables the evaluation of the design of busbars or trunkings, leading to the optimization of their layouts and even of their shapes for electromagnetic considerations.

A Self-Tuning Vector Controlled Induction Motor with a Low-Count Encoder for Naval Applications
Peyman Niazi and Hamid A. Toliyat
In industrial speed and torque controlled drive systems, and in many propulsion applications, the closed loop control system is based on the measurement of speed or position of the motor using a shaft encoder. Using a high precision encoder leads to high cost of the control system. Moreover, it may cause problems at high speed due to high frequency encoder output signal. In this case, use of a low-cost low-precision encoder is more favorable in control system. This paper presents the implementation of a vector controlled induction motor system using a 64-pulse per revolution encoder. In order to solve the low precision problem in speed measurement, an enhanced speed measurement method has been used. The control system also has been equipped with an algorithm for tuning up the change of rotor resistance. This algorithm also will help the control system to maintain the maximum torque per amp condition.

A Strategy for Improving Reliability of Motor Drive Systems With a Matric Converter
Sangshin Kwak and Hamid A. Toliyat

Even though matrix converter drives are more vulnerable to system faults due to their requirement of many power switches, little effort has been expended on improving the reliability of the drives. In this paper, a novel control scheme for continuous, fault-tolerant operation of the matrix converters is presented to improve their reliability. The proposed PWM modulation strategy of the matrix converter allows disturbance free operation of the matrix converter drives by keeping the same rotating MMF even with complete loss of one leg of the converter or motor phase. Theoretical analyses and the derivation of the new PWM strategy are described. Experimental results are provided to verify the feasibility of the proposed scheme.

Some Considerations in High Power Motor Drive Systems for Ship Propulsion
Y. Wei, J. Junghans, J. C. Balda, F. D. Barlow, A. Elshabini

Two key issues with high power motor drive systems are the selection of the power switches in order to minimize the power losses, as well as the thermal management of these devices. The first part of this paper initially compares two Gate Commutated Thyristors and two high-voltage Insulated Gate Bipolar Transistors for a three-level three-phase inverter for a 24-MW 4.16-kV propulsion system. The comparison is based on the inverter switch arrangement, power losses, and cooling system requirements. The second part of this paper describes a test bench for spray-cooling research at the University of Arkansas and presents experimental results to illustrate the feasibility of this technology.

On the Detection of Rotor Faults in Permanent Magnet Machines
Wiehan le Roux, Satish Rajagopalan, Thomas G. Habetler, Ronald G. Harley

Like induction motors, permanent magnet (PM) machines have no brushes or mechanical commutators, and therefore low maintenance, but in addition the PM machines have a higher torque/power density, as well as higher efficiencies and power factor. More, and more PM machines are therefore being used, often in critical high performance applications. Fault diagnosis and condition monitoring of PM machines is therefore assuming a new importance. Early detection of faults and asymmetries would allow preventive maintenance to be performed and provide sufficient time for controlled shutdown of the process, thereby reducing the costs of outage time and repairs. The range of faults on PM machines includes stator faults, rotor faults, and inverter faults. Though considerable research has been reported in the diagnosis of induction motor faults, much research remains to be done in the diagnosis of particularly rotor and bearing faults in PM machines. The analysis, and practical implementation of PM machine rotor faults is described in this paper.

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