7 research outputs found
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Induction motor performance testing with an inverter power supply, part 1
The development of high-power density electrical machines continues to accelerate, driven by military, transportation, and industrial needs to achieve more power in a smaller package. Higher speed electrical machines are a recognized path toward achieving higher power densities. Existing industry testing standards describe well-defined procedures for characterizing both synchronous and induction machines. However, these procedures are applicable primarily to fixed-frequency (usually 60 or 50 Hz) power supplies. As machine speeds increase well beyond the 3600-rpm limitation of 60-Hz machines, a need for performance testing at higher frequencies is emerging. An inverter power supply was used to conduct a complete series of tests on two induction motors (0.5 and 1.0 MW) with speeds up to ~5000 rpm. The use of a nonsinusoidal power supply with limited power output capability required the development of measurement techniques and testing strategies quite different than those typically used for 60/50 Hz testing. Instrumentation and techniques for measuring voltage, current, and power on harmonic rich waveforms with accuracies approaching 1% are described. Locked-rotor and breakdown torque tests typically require large kVA input to the motor, much higher than the rated load requirement. An inverter sized for the rated load requirements of the motor was adapted to perform locked-rotor and breakdown torque tests. Inverter drive protection features, such as anti-hunting and current limit that were built into the inverter had to be factored into the test planning and implementation. Test results are presented in two companion papers. This paper (Part 1) correlates test results with the results of an algorithmic induction motor analysis program. Part 2 presents the test results compared with a Matlab simulation program and also provides a comprehensive discussion of the instrumentation that was essential to achieve testing accuracy. Correlating test results with calculated valu- es confirmed that the testing techniques developed during this testing program are useful for evaluating high-speed, high-power density electrical machineryCenter for Electromechanic
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Arc Initiation for the Electromagnetic Powder Deposition Gun
The instrumentation, interpretation of data, and subsequent decisions regarding the direction of system development are discussed. Important system parameters, their impact on system performance, and techniques to measure them are presented. The electromagnetic powder deposition system is based on railgun technology developed by the Department of Defense. The system drives an ionized plasma sheet down the length of a railgun, reaching a final plasma velocity of 4 km/sec. The high velocity plasma, in turn, snowplows a shock compressed gas column in front of it. This gas column sweeps through a powder cloud and accelerates it by viscous drag to a final velocity of 2 km/sec. Important system parameters include particle velocity, gas velocity, gas column pressure, and plasma propagation and velocity. Diagnostic tools include pressure transducers, a high speed digital framing camera, fiber optics and magnetic probes.Center for Electromechanic
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Designing Pulse Power Generators
When the performance criteria for a pulsed power generator is power density, and the duty cycle remains short ( s), then copper coils with an exciter are favored over permanent magnet rotors. If the permanent magnets are replaced with copper coils, steel, and an exciter, with the same total weight, the copper coil alternative will return a higher magnetomotive force/weight, and thus a higher power density system. A variable metric optimization is completed for a generator, assuming the objective is to charge a capacitor bank. The equations governing allowed current density in capacitor charging applications and alternating current/direct current (ac/dc) resistance ratios are derived.Center for Electromechanic
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Electromagnetic Powder Deposition Experiments
The US Department of Defense (DoD) and commercial entities are dependent on chemical plating and coating processes to replace worn or eroded material on damaged parts. Logistics Centers have been forced to consider replacement materials for repair operations due to the tightening of government regulations on the use of toxic and hazardous materials. This paper describes a new process capable of fulfilling many of these requirements. Existing state-of-the-art thermal spray processes (HVOF, D-gun, plasma spray) are limited to powder velocities of about 1 km/s because they rely on the thermodynamic expansion of gases. A new thermal spray process using electromagnetic forces can accelerate powder particles to a final velocity in excess of 2 km/s. At this velocity, powder particles have sufficient kinetic energy to melt their own mass and an equivalent substrate mass on impact. The energetics of the process allow fusion bonding of greater strength than that created by low velocity processes as well as improved coating density. This paper describes the laboratory system designed and constructed to conduct proof of principle experiments. Results of the experiments are presented along with high speed photographs of powder particles confirming system modeling and performance. The paper concludes with a discussion of the future direction of the programCenter for Electromechanic
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A New Electromagnetic Powder Deposition System
Existing state of the art thermal spray processes (HVOF, D-Gun, Plasma Spraying) are limited to powder velocities of about 1 km/sec because they rely on the thermodynamic expansion of gases. A new thermal spray process using electromagnetic forces can accelerate powder particles to a final velocity of up to 2 km/sec. At this velocity powder particles have sufficient kinetic energy to melt their own mass and an equivalent substrate mass on impact. The process is based on railgun technology developed by the Department of Defense. A railgun is filled with argon gas and a high energy electrical pulse, provided by a capacitor bank, drives the gas down the railgun to a final velocity of up to 4 km/sec. This gas passes over a powder cloud and accelerates the powder through drag forces. The electrical and powder discharge frequency can be adjusted so that the deposition rate and thermal input to the substrate can be controlled.Center for Electromechanic
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The Diagnostic History of a New Electromagnetic Powder Deposition System
This paper describes the diagnostic tools used in the development of a new electromagnetic powder deposition system.Center for Electromechanic
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Scaling Analysis of the Electromagnetic Powder Deposition Gun
The electromagnetic powder deposition (EPD) system employs high velocity gas flow to accelerate powder material to conditions required for high strength plating. The gas flow, however, is not continuous; rather it consists of bursts generated by an electromagnetic railgun and pulsed power system. Each gas burst is created by a high pressure plasma arc which fills a transverse section of the gun. This current carrying arc is driven by the railgun Lorentz force (magnetic pressure) and acts much like a piston, which via a snowplow process accelerates and compresses an ambient gas column to the flow speed required to accelerate powder particles. Analysis of the total system was carried out to provide scaling relations which give guidance in design of the system. Plating considerations define a desired powder velocity; this combined with the choice of working gas and ambient pressure determines the velocity and duration of each gas burst. Selection of gun geometry completes the definition of the pulsed power system requirements. An outline of the analysis is presented along with the physical models used.Center for Electromechanic