Inductor inductors

Inductors. Inductors have many turns of conductor wrapped around a cylinder if the cylinder is of a magnetic material, then the inductance L is much increased. L is measured in henrys. Two intertwined turns of wire will have mutual inductance M a current through one loop will induce a current in the second loop. The units of M are the same as for L. 

Two difierent components contribute to impedance the resistive or real component due to resistors and the reactive or imaginary component from AC circuitry elements, such as capacitors, inductors, etc. Unlike the resistive component, the reactive impedance affects not only the magnitude of the AC wave but also its time-... 

The inductively coupled plasma [19] is excited by an electric field which is generated by an RF current in an inductor. The changing magnetic field of this inductor induces an electric field in which tire plasma electrons are accelerated. The helicon discharge [20] is a special type of inductively coupled RF discharge. 

Equally important as tape casting in the fabrication of multilayer ceramics is thick film processing. Thick film technology is widely used in microelectronics for resistor networks, hybrid integrated circuitry, and discrete components, such as capacitors and inductors along with metallization of MLC capacitors and packages as mentioned above. 

X X cote material for various inductors, transformers, and TV deflection units... 

Fig. 5. Complex magnetic permeabihty vs frequency for a series of ferrites used for power transformers and inductors at 25°C, S <0.1 mT (—) represents real parts ]l (-----------------------) show the imaginary parts ]l". The arrows indicate the frequencies where tan6 = fi/fi = 1 (57).

Coreless furnaces derive their name from the fact that the coil encircles the metal charge but, in contrast to the channel inductor described later, the cod does not encircle a magnetic core. Figure 8 shows a cross section of a typical medium sized furnace. The cod provides support for the refractory that contains the metal being heated and, therefore, it must be designed to accept the mechanical loads as well as the conducted thermal power from the load. 

The term channel induction furnace is appHed to those in which the energy for the process is produced in a channel of molten metal that forms the secondary circuit of an iron core transformer. The primary circuit consists of a copper cod which also encircles the core. This arrangement is quite similar to that used in a utdity transformer. Metal is heated within the loop by the passage of electric current and circulates to the hearth above to overcome the thermal losses of the furnace and provide power to melt additional metal as it is added. Figure 9 illustrates the simplest configuration of a single-channel induction melting furnace. Multiple inductors are also used for appHcations where additional power is required or increased rehabdity is necessary for continuous operation (11). 

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. 

Metal contained in the channel is subjected to forces that result from the interaction between the electromagnetic field and the electric current in the channel. These inward forces produce a circulation that is generally perpendicular to the length of the channel. It has been found that shaping the channels of a twin coil inductor shown in Figure 10 produces a longitudinal flow within the channel and significantly reduces the temperature difference between the channel and the hearth (12). 

Hearth. The hearth of a channel induction furnace must be designed to satisfy restraints that are imposed by the operating inductor, ie, the inductor channels must be full of metal when power is required, and it is also necessary to provide a sufficient level of metal above the channels to overcome the inward electromagnetic pressure on the metal in the channel when power is appHed. Once these requirements are satisfied, the hearth can then be tailored to the specific appHcation (13). Sizes range from stationary furnaces hoi ding a few hundred kilograms of aluminum to rotating dmm furnaces with a useful capacity of 1500 t of Hquid iron. 

A typical m el ter iastalled in a medium sized brass foundry contains 4500 kg of brass and its inductor is rated 500 kilowatts. Brass is an alloy containing copper and zinc. Zinc vaporizes at temperatures weU below the melting temperature of the alloy. The channel iaductor furnace s low bath temperature and relatively cool melt surface result in low metal loss and reduced environmental concerns. Large dmm furnaces have found use in brass and copper continuous casting installations. 

Alternatively, induced air flotation (lAF) can be employed, in which air bubbles are generated through an inductor. The removal mechanism is the same as the DAF. 

In maldug electrochemical impedance measurements, one vec tor is examined, using the others as the frame of reference. The voltage vector is divided by the current vec tor, as in Ohm s law. Electrochemical impedance measures the impedance of an electrochemical system and then mathematically models the response using simple circuit elements such as resistors, capacitors, and inductors. In some cases, the circuit elements are used to yield information about the kinetics of the corrosion process. 

Instead of a charging capacitor C. a large size series inductor L is introduced in the d.c, link (Figure 6.29).. Since V = L di/d/. the larger the value of L, the lower will be the current overshoots (d/7d/) and a near-constant d.c. link current source is obtained for the inverter unit. 

A large inductor in the d.c. link may also play the following roles ... 

Figure 6.34 Application of inductor and capacitor with a controlled bridge rectifier (for control of d.c. machines)...

L - Inductance of the supply source L, - Inductor to smooth ripples... 

L2- Inductor to absorb the trapped energy up to Ic)[par1ly absorbed by the feeder s own impedance and ofher feeders... 

The inductor on the input side also suppresses the harmonics in the incoming supply, as high Lj will provide a high impedance path to higher harmonics. For suppression of harmonics, where the supply system is already substtintially distorted, tiddilional L-C... 

When there is no dedicated transformer and these circuits are connected on the system bus directly a large inductor will be essential at the incoming of the static circuits, sufficient to absorb the trapped charge within the transformer and the interconnecting cables up to the converter unit. The size of the inductor can be calculated depending on the size (kVA) of the distribution transformer, its fault level and the characteristics of its current limiting protective device. An inductor sufficient to absorb //, L of the transformer and the cables may be provided at the incoming of the sialic circuits. 

In addition, it would also help to dampen the amplitude of the arriving surge. The u,se of inductor on the load side to provide an impedance to the arriving surges with a view to suppressing them is not good practice, for it may diminish the p.f. of the circuit and also catise a voltage drop across it, which may affect the machine s performance. 

Variable a.c. voltage and frequency IGBT or thyristor converter (7) Inductor... 

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