Electromagnetic Thrust Bearing for a Homopolar Machine: Experimental Implementation

Development of large, inertial pulsed power supplies is essential to the success of the controlled thermonuclear research program. A very attractive candidate for this supply is the homopolar motorgenerator which can produce the large current pulses (~lOOKA) necessary for the confinement and compression magnetic fields needed on the large fusion feasibility experiments. For a radial current flow, axial magnetic field configuration, the machine rotor is unstable to movement in the axial direction. Therefore a large mechanical thrust bearing is normally used which adds to the frictional losses and reduces the machine's efficiency. However, these losses could be reduced substantially by replacing the mechanical bearing with an electromagnetic thrust bearing. This report discusses the experimental implementation of an electromagnetic thrust bearing on the 0.5MJ homopolar machine presently in operation at The University of Texas at Austin. A control system describing the electromagnetic thrust bearing is formulated and the system stability is determined. The circuitry is then described which produces the required differential field current and monitors the position of the rotor. The latter is done by a position sensing unit consisting of an LED and a phototransistor. The former is done with an operational amplifier circuit that generates equal and opposite voltages which drive the two SCR field supplies in a manner to create the required differential current. For a static rotor, test results show that a restoring force is generated and that the rotor can be stabilized against the axial forces.Center for Electromechanic

Electromagnetic Thrust Bearing for a Homopolar Machine--Theoretical Analysis

Development of large, inertial pulsed power supplies is essential to the success of the controlled thennonuclear research program. A very attractive candidate for this supply is the homopolar motorgenerator which can produce the large current pulses (~lOOKA) necessary for the confinement and compression magnetic fields needed on the large fusion feasibility experiments. For a radial current flow, axial magnetic field configuration, the machine rotor is unstable to movement in the axial direction. Therefore a large mechanical thrust bearing is normally used which adds to the frictional losses and reduces the machine's efficiency. However, these losses could be reduced substantially by replacing the mechanical bearing with an electromagnetic thrust bearing. This is based on the principle of controlling the axial motion of the rotor by differential control of the two halves of the field. This report describes the theoretical analysis of such a system based on Maxwell's equations and the co-energy principle. The static force acting on the rotor and the inductance of the field coil are calculated as a function of the field current, the rotor displacement from magnetic center, and the differential current. Additionally the equation of motion of the rotor including the feedback control system which drives the differential current in the field coils is calculated. Results are obtained for two sets of initial conditions: 1) the rotor is initially displaced and 2) an initial impulse- like force is applied to the rotor in the axial direction. It is shown that for initial displacements less than lo- 3m and/or impulse forces less than 3Nt-sec stability can be achieved for the 0.5MJ homopolar machine presently in operation.Center for Electromechanic

Homopolar Motor Generator for Inexpensive Inertial Energy Storage

Center for Electromechanic

Characteristics of a Homopolar Machine as a Power Supply for Large Pulsed Magnetic Fields for Fusion Experiments

Inexpensive and reliable methods of storing and transferring large amounts of energy (>50 MJ) are essential to continued progress in controlled fusion research. One particularly attractive means of doing this, for slow time scale requirements (10-100 sec), is to use a homopolar generator in a pulsed mode of operation. A detailed design study of a 55 MJ homopolar machine to power the toroidal field of the Texas Turbulent Torus is being carried out at The University of Texas. This unit is designed to deliver a peak current of 35 kA, at 210 volts, to the field coils of the Texas Torus in 10 sec. In addition a 0. 7 MJ working bench model of the homopolar machine has been built and is currently being used to test the design of the large unit. These tests include mechanical considerations such as stress, bearing loading, and heating, and electrical considerations such as stability, speed control, and field compensation.Center for Electromechanic

Homopolar Motor Generator for Inexpensive Inertial Energy Storage

The Homopolar Motor-Generator Bench Model machine designed and fabricated during the summer and early fall of 1972 has been upgraded with several modifications and successfully tested during this progress period. During this same progress period the design for the 50 Mega-joule Homopolar Motor-Generator was completed and preliminary cost data compiled on major components. A review of the design criteria for the 50 Mega-joule Homopolar Motor-Generator revealed a change in design would be necessary to meet the changing requirements for such a machine and preliminary design alternatives have been conceived.Center for Electromechanic

Homopolar Motor Generator Designs for Cheap Inertial Energy Storage

One of the limitations to the research in fusion power is the need for a cheap method of storing large amounts of energy. This energy is needed for the main confinement magnetic field in the next Tokamak and must be capable of transfer from the store to the coil in a short time (1 to 10 sec.). Conventional power supplies are unnecessarily expensive since it is quite possible that the existence of the field for l or 2 seconds would be sufficient. An inertial energy storage system utilizing a homopolar generator was studied for feasibility and found to be satisfactory resulting in the design, construction and testing of a bench model along with the design of an intermediate 50 M.J. machine to power the present Texas Tokamak.Center for Electromechanic

As Apocynaceae da região de Poços de Caldas, Minas Gerais, Brasil Apocynaceae of Poços de Caldas region, Minas Gerais State, Brazil

Este trabalho consiste no estudo florístico da familia Apocynaceae em Poços de Caldas, dada sua representatividade na região e o valor fitoquímico e ornamental de várias de suas espécies. Foram encontradas 17 espécies distribuídas entre 8 gêneros: Aspidosperma Mart e Zucc., Condylocarpon Desf., Forsteronia G.F.W. Mey., Macrosiphonia Muell. Arg., Mandevilla Lindl., Peltastes R.E. Woodson, Prestonia R. Br. e Rauvolfia L.<br>A floristic study of the family Apocynaceae im Poços de Caldas was carried out, since the family is well represented in the region and many species have phytochermical and ornamental value. The family is represented by 17 species distributed in 8 genera: Aspidosperma Mart e Zucc., Condylocarpon Desf., Forsteronia G.F.W. Mey., Macrosiphonia Muell. Arg., Mandevilla Lindl., Peltastes R.E. Woodson, Prestonia R. Br. and Rauvolfia L

Investigation of the Homopolar Motor Generator as a Power Supply for Controlled Fusion Experiments

With the impending construction of large controlled fusion feasibility experiments, the need for reliable, inexpensive inertial energy storage to power the confinement magnetic field ls becoming more urgent. To investigate the possibility of using a homopolar machine for this task we have carried out a series of electrical and mechanical tests on a O. 5 MJ unit operating as a pulsed power supply. The machine ls motored up to a design speed of 6000 RPM using a 150 kW SCR power supply, and then, upon disconnecting the supply and connecting a load (short circuit), current pulses of up to 13 kA with a rise time of 25 ms are generated. The peak current and pulse decay time are limited by the armature circuit resistance, RA. This in tum depends primarily on the amount of rotor surface covered by the brushes which, in the ca1e of this machine, ls only 1% leading to a relatively high RA of 4 x 10-4 n. In addition, we observe that up to 80% of the stored energy ls delivered to the load. Motoring efficiencies are considerably less due to friction of the brushes and loading of the thrust bearing. In this connection we are testing an electromagnetic thrust bearing that is based on the principle of restoring the rotor to a position of magnetic equilibrium by differentially exciting field coils on each side of the central plane perpendicular to the axis of rotation. This process involves a photoelectronic device to sense the position of the rotor in order to control the field supplies. Based on results from our small model, we are in the process of constructing a 5 MJ single rotor machine capable of generating 100 kA at 5500 RPM and 45 volts. This model will have substantially higher motoring efficiency and lower armature circuit resistance. Design features of this machine are discussed.Center for Electromechanic

Homopolar Motor-Generator for Inexpensive Inertial Energy Storage

Center for Electromechanic