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Schematic of the Birkeland or Field-Aligned Currents and the ionospheric current systems they connect to, Pedersen and Hall currents. [1]A Birkeland current (also known as field-aligned current, FAC) is a set of electrical currents that flow along geomagnetic field lines connecting the Earth's magnetosphere to the Earth's high latitude ionosphere.
A magnetohydrodynamic generator (MHD generator) is a magnetohydrodynamic converter that transforms thermal energy and kinetic energy directly into electricity.An MHD generator, like a conventional generator, relies on moving a conductor through a magnetic field to generate electric current.
Thermomagnetic motors (also known as Curie wheels, [1] Curie-motors [2] [3] and pyromagnetic motors [4]) convert heat into kinetic energy using the thermomagnetic effect, [5] i.e., the influence of temperature on the magnetic material magnetization.
Schematic view of the different current systems which shape the Earth's magnetosphere. In many MHD systems most of the electric current is compressed into thin nearly-two-dimensional ribbons termed current sheets. [10] These can divide the fluid into magnetic domains, inside of which the currents are relatively weak.
Separately-excited generators like this are commonly used for large-scale power transmission plants. The smaller generator can be either a magneto with permanent field magnets or another self-excited generator. A field coil may be connected in shunt, in series, or in compound with the armature of a DC machine (motor or generator).
An inrush current limiter is a device or devices combination used to limit inrush current. Passive resistive components such as resistors (with power dissipation drawback), or negative temperature coefficient (NTC) thermistors are simple options while the positive one (PTC) is used to limit max current afterward as the circuit has been operating (with cool-down time drawback on both).
The linear generator also allows the control of the resistance force, and therefore a better control of the piston's movement and of the reaction. The total efficiency (including mechanical and generator) of free-piston linear generators can be significantly higher than conventional internal combustion engines and comparable to fuel cells.
The typical efficiency of TEGs is around 5–8%, although it can be higher. Older devices used bimetallic junctions and were bulky. More recent devices use highly doped semiconductors made from bismuth telluride (Bi 2 Te 3), lead telluride (PbTe), [10] calcium manganese oxide (Ca 2 Mn 3 O 8), [11] [12] or combinations thereof, [13] depending on application temperature.