Eddy current couplings

Losses are high because of field system, but comparatively much less than fluid and eddy current couplings. At lower speeds the losses rise in the form of motor inefficiency... 

Figure 8.9(b) A general scheme illustrating speed control by feedback control system using an eddy current coupling... 

A = fraction of superconductor by volume fio = permeability of free space p = composite resistivity Pa = dynamic resistivity Px = resistivity transverse to the filaments Pll = resistivity parallel to the filaments Te = eddy current (coupling current) relaxation time Th = hysteresis driven transport current relaxation time constant... 

Lew frequency Eddy current probing For frequencies below some 100 Hz the SQUID is coupled with a completely superconducting flux antenna. This antenna has to be within the cryogenic vessel. The Eddy current excitation is done in a conventional way. But care must be taken, that interference between the excitation field and the flux anteima and SQUID is... 

As stated above the SQUID amplifier demands a low inductance Eddy current probe in order to be able to amplify signals up to 1 MHz. Low inductance Eddy current probes can be obtained by reducing the number of turns and by loosing the magnetic coupling between the tums. So magnetic cores should be avoided as well as tight wounded tums. For this purpose planar coils are the best... 

Sometimes a coupling insulation as indicated at location 2 in Figure 10.8 may also prevent the eddy currents forming a closed circuit and generate the bearing currents. 

The advent of new, more reliable, and sensitive vibration instrumentation such as the eddy-current sensor and the accelerometer coupled with modern... 

Electrical output transducers exist in many forms and consist simply of elastic elements coupled with suitable displacement transducers such as capacitance, inductance and reluctance pick-ups, certain types of strain gauge, piezoelectric elements, potentiometers and eddy current probes. A selection of these is described in the following paragraphs. 

Hyperthermia and thermoablation have been accomplished using capacitive or inductive coupling of rf fields (10-100 MHz), microwaves (> 300 MHz), ultrasound, lasers or external heat [171-177]. Macroscopic metal implants of Cu and other high-conductivity metals have been used to induce eddy-current heating. The absorbed power per mass is called the specific absorption rate (SAR), which can be expressed as... 

Inclusions Processing (weldments) Ferrous and nonferrous Radiographic method Eddy current method is used in thin-wall welded tubing coupled with reference standards... 

When we say, power consumption, we usually refer to the main motor. It reflects the load on the motor because of useful work, as well as the power needed to run the motor itself (losses because of eddy currents, friction in couplings, etc.). 

In this case, we see that heat radiates from both the sides and the top of the melt even though the crucible is being heated by the eddy-currents from the RF-generator coupling. Note also that the crystal being pulled also radiates heat. However, this is for a static crucible. The circular currents set up in the melt are the results of the crystal being turned as it grows. The circular heat flow pattern causes the surface to radiate heat. 

Inductively Coupled Plasma Discharge An electrodeless radiofrequency discharge produced by magnetically induced eddy currents in flowing argon confined in a quartz tube at atmospheric pressure. liquids, powders, gases 6000-10,000... 

With power in the load coil, the Ar stream is sparked with a Tesla coil discharge to create seed Ar ions. As these reach the magnetic field created by the load coil, they are accelerated and collide with other Ar atoms to produce more ions. Electrons and ions flow in closed annular paths in the time-varying magnetic fields. These eddy currents cause ohmic heating that leads to further ionization and generate electromagnetic fields that couple with those of the r.f. output to... 

The mutual inductance is represented by shunt inductor L , since the magnetizing current is not coupled to the load. A resistor Rc is also placed in shunt, to represent the core loss due to hysteresis and eddy currents in the core. 

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