Browsing by Subject "induction"
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Item Design and analysis of passive homopolar null flux bearings(IEEE, 2005-03) Davey, K.R.; Filatov, A.; Thompson, R.C.Electrodynamic Maglev systems (EDSs) and passive magnetic bearings (PMBs) generate magnetic forces by induction through the movement of permanent or superconducting magnets past conducting coils. Nearly all EDSs and PMBs use a flux coil exposed to changing magnetic fields in the rotation or travel direction. An unusual variant eliminates discrete coils by using field structures that do not vary in the direction of rotation. We discuss the design and analysis of this homopolar variant in this paper. We believe that this is the first combined passive damper/axial support bearing, and we present here the first generalized solution of its governing equations. Actuated brushes during motoring and generating simplify energy exchange when the device is used for flywheel energy storage.Item Electromagnetic Induction Launchers(IEEE, 1986-11) Driga, M. D.; Weldon, W. F.; Woodson, H. H.The electromagnetic launcher consists of a system of stator coils producing a traveling field which accelerates an armature carrying currents induced by the traveling field (induction accelerator [1,2]) or persistent currents supplied from otner sources (synchronous accelerator [2,10]). The fact that their armature has no electrical contact with the stator, essentially riding on the crest of a traveling magnetic wave, makes induction accelerators very attractive for a large number of applications. This paper is devoted exclusively to the accelerator of the induction type. Efficiency considerations require that the traveling wave should accelerate at approximately the same rate as the projectile. This can be achieved either using variable (increasing) winding pitch or a continuously increasing power supply frequency or a combination of both. A new dimension was added to the induction coaxial accelerator technology with the definition at the Center for Electromechanics at The University of Texas at Austin (CEM-UT) of a new electrical machine, the Rising Frequency Generator (RFG) representing a more attractive integrated power source for induction accelerators which had previously been forced to conform to constant frequency power supplies. This paper outlines the principles of design and shows two applications of induction coaxial launchers; a half-scale aircraft launcher in which the system also acts as an electromagnetic brake, stopping the shuttle and driving it in the opposite direction, and a high performance, 18-m long launcher capable of accelerating a 1-kg aluminum projectile to a velocity of 10 km/s at an average acceleration of 250,000 G.Item The equivalent T circuit of the induction motor: its nonuniqueness and use to the magnetic field analyst(IEEE, 2006-04) Davey, K.R.The equivalent T circuit of an induction motor is found in every engineering motors book and is becoming increasingly important with the popularity of vector control. The values used in the circuit are used to dictate the necessary gating signals for the pwm inverter. It is the de facto standard bridge between the field analyst and the motor controller. These parameters are not unique. Force, energy, voltage, and secondary power dissipation can be shown to relate to the product of synchronous reactance and the coupling coefficient of the rotor and stator. The mutual reactance, the secondary inductance, and secondary resistance are non-unique. Yet this surprising feature can be used as a solution integrity check for the field analyst.