Modular Multi-Mode Power Supplies for Naval Power Systems John Herbst, Joe Beno, Hamid Ouroua, Robert Hebner, Scott Pish, Jon Hahne University of Texas at Austin Center for Electromechanics ASNE Day 2015 March 3 – 5, 2015 Arlington, VA

Presentation Overview Rotating Electric Machines for Naval Applications Modular Multi-Mode Power Supplies (M3PS) Combat Hybrid Power Supply (CHPS) Compensated Pulsed Alternators Conclusions

Rotating Electric Machines for Naval Applications Rotating electric machines are a critical element of every naval vessel in service today Rotating electric machines address a broad range of naval applications: Simple electric motor driven loads Prime/auxiliary power generation Emerging high speed generation Propulsion Induction, WF synchronous, PM EMALS pulsed power system Specialized rotating electric machines are already an important part of the US Navy’s toolbox Providing robust, reliable solutions for critical mission loads http://www.navyrecognition.com/index.php?option=com_content&task=view&id=932

M3PS Concept Modular system of high performance rotating electric machines combining inertial energy storage with continuous and pulsed power capabilities Builds on successful EMALS concept Provide stand-alone solutions or can be integrated into hybrid systems as part of an Energy Magazine Scalable systems to meet range of applications Fully integrated topology to maximize energy and power density

Flywheel Topologies Non-Integrated Topology • Larger than other topologies, but may have most simple assembly • Maximum use of conventional M/G systems and technology • Flexible / adaptive design • Power generation outside of vacuum • Requires shaft seal and coupling Partially-Integrated Topology • Smaller and more efficient than non- integrated • Good use of available M/G technology, but integration required • Good design adaptability • Favors use of PM generator • Heat generation on rotor requires careful engineering Fully-Integrated Topology • Most compact system • Special purpose flywheel system • Favors use of PM generator • Heat generation on rotor requires special engineering • Rotating magnets at large radius • Uses arbor or magnetic bearings to match rotor growth

Combat Hybrid Power Supply

Combat Hybrid Propulsion System (CHPS) Dual use flywheel energy storage “Inside-out” arbor-less technology Continuous duty and pulse loads for offensive and defensive systems Rotor assembly and material property matching key for life requirements Demonstrated Assembly of multi-pole magnetic rotor subassembly Assembly of full scale, liquid cooled stator Static torque, voltage, and cooling testing Full scale magnetic bearing under static load with simulated rotor growth Combat Hybrid Power Systems (CHPS) Flywheel 5-10 MW (peak), 4.5 MW (cont.), 7 kW-h CHPS Component Verification S 3911.0009 S 3911.0235

CHPS-A Machine

CHPS-A Performance Add composite rings to increase energy storage Upgrade design for higher peak/continuous power

Complete CHPS Flywheel System Lab Bearing Amplifiers Flywheel Rectifier Assembly Lab Safety Disconnect Converter Transformer

CHPS-N Characteristics (evolving) Multifunction machine Services multiple loads that require intermittent electric power UPS Dark start Power quality improvement Small size Fits through a 26”- diameter hatch Advanced technologies for performance enhancement High speed machine technology Advanced composite banding Innovative heat transfer techniques Novel bearings Shock load mitigation Advanced materials Low loss / High temperature

Compensated Pulsed Alternators

Compensated Pulsed Alternators Conceived at University of Texas in late ’70s Original application was laser power supply for Lawrence Livermore inertial confinement fusion program Wound field synchronous generator with compensating windings or eddy current shields Low impedance High airgap flux densities Gigawatts for milliseconds Capable of directly driving large pulsed loads Demonstrated synchronized discharge of parallel machines Megamp Output Current Pulses

Armature Compensation Use image currents in compensating winding or conductive eddy current shield to contain magnetic fields from armature output currents Minimizes internal impedance Multiple topologies and compensation techniques Iron core, air core, rotating field, rotating armature, single- or multiphase Active, passive, selective passive External excitation or self excitation

Compensation Techniques Active compensation features a compensating winding in series with the armature winding Sharp pulse with fast rise time Passive compensation uses a conductive eddy current shield Essentially sinusoidal output pulse Selective passive compensation uses a shorted compensating winding rotated azimuthally relative to the main armature winding Can be tailored for a variety of output pulse shapes

PA Development History

Latest PA Designs Latest PA designs are air core machines without compensation Highest power density Self-excited system “Seed” current injected into rotating field winding Resultant armature output is rectified and fed back onto the field winding Armature output is switched into load when peak field current is achieved

2004 Internal Design Study

Additional PA Benefits System can be designed to minimize transient loading on ship power system Take advantage of operation over wide speed range to buffer supply System stores energy for multiple high energy pulses Stored energy available to support other transient loads or to provide active filtering

Technology Comparison 12 MJ Capacitor Bank Acknowledge Age of caps Mention switches on compulsator Need motor/generator for flywheel 22 MJ Compulsator 480 MJ Flywheel

Summary/Conclusions Rotating electric machines are already being used to address critical mission loads for the US Navy Modular Multi-Mode Power Supplies (M3PS) are a family of advanced rotating machines that can effectively address a wide range of Navy applications M3PS concepts offer improved energy & power density relative to alternative pulsed power systems M3PS concepts can also provide additional support for the ship power system when not being used for their primary mission load