Air-cored coil

This relationship is the Faraday effect. The magnetic field is generated in an air core coil inside of which is a rod made from glass having a high Verdet constant. Now,... 

Answer An air-cored coil would seem perfect as an inductor, especially since it would never saturate. However, the number of turns required to produce a given inductance would be impractically large, and so we would get unacceptable copper losses. Further, since there is nothing to channel (constrain) the flux lines, the air-cored inductor would spew electromagnetic interference (EMI) everywhere. 

The theoretical equations for coil impedance calculation in air are provided by (Auld, Muennemann, and Winslow 1981) that follow from original Dodd and Deeds equations (Dodd and Deeds 1968, Dodd and Deed 1975). Consider an air-core coil located... 

In this paper we use the layer approximation 1 in order to compute the change in impedance of an air-core coil symmetrically located above a conducting cylinder of finite thickness d (a coin, for example). The axis of the coil coincides with the axis of the cylinder. In this case formula 1 can be written in the form ... 

These simulations are valid for the air-core coil based conductivity measurements with infinite size of metal plates, consisting of one or several metal layers. The infinite size is typically not very significant constraint for real-life measurements, as the eddy current electro-magnetic fields are decreasing quickly in the media. Only a few millimetres larger metal plate than the sensor s size is typically enough to have reasonably precise results. 

Alternatives to single air-core coil measurement setup... 

The mentioned single air-core coil measurement solution has been further investigated. Alternative copper-wire wounded coils with various numbers of turns have been tried. Also... 

S. Burke and M. Ibrahim, Mutual impedance of air-cored coils above a conducting plate, Journal of Physics D Applied Physics, vol. 37, no. 13, p. 1857, 2004. 

Unlike an air core, the inductor coil now has an iron core that may be provided with air gaps or non-magnetic... 

Some generators have the damper bars connected to a ring at either end of the pole structure, which provides some damping action from the quadrature axis. This provides a set of short-circuited coils in the quadrature axis, which are air cored and able to repel the flux that is attempting to enter their region. 

Air Core Cryogenic Magnet Coils for Fusion Research and High-Energy Nuclear Physics Applications (5) 13 ORTHO-PARA CATALYSTS Efficient Utilization of Ortho-Para Catalyst (3) 64... 

Air-core solutions and models are more precise and stable than of the magnetic cores. The experimental work done so far, also shows that the single coil setup is not only simpler to model and calculate, but is giving also much better results in the mentioned frequency band. Still, our experiments show that for some specific and limited low frequency band (e.g. in the 10 kHz region) the through-the-metal-plate two-coil setup [11] can give better absolute measurement result. 

Single coil air-core measurement solutions have been investigated [14] (Martens et al 2011) experimentally and compared with the theoretical models [3, 5] (Dodd and Deeds 1968, The odoulidis and Kotouzas 2000). 

AIR CORE CRYOGENIC MAGNET COILS FOR FUSION RESEARCH AND HIGH-ENERGY NUCLEAR PHYSICS APPLICATIONS ... 

Inductor. The channel inductor assembly consists of a steel box or case that contains the inductor refractory and the inductor core and coil assembly. The channel is formed within the refractory. Inductor power ratings range from 25 kilowatts for low temperature metals to 5000 kilowatts for molten iron. Forced air is used to cool the lower power inductors, and water is generally used to cool inductors rated 500 kilowatts or more. 

As Sf air gap core or armature then a small change in x will produce a large variation in fr. The self-inductance 5 of the coil in Fig. 6.14a is the total flux linked per unit current. Thus, from equation 6.18 ... 

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