Preface to the lecture, 1
Yüklə 4,22 Mb. Pdf görüntüsü
|
64
noise
Fig. 4.7: The power density shown against frequency for noise (a) according to Kupfmuller ,
as well as for dielectric losses of a capacitor (also a) and for eddy current losses (b) according to Mevl (b in visible duality to a).
Verlag Berlin, 12. Auflage 1988, ISBN 3-540-18403-1
Wirbelstromkupplungen, Dissertation Universitat Stuttgart 1984 properties ____________________________________________________________________________ 65
4.7 Noise If, according to the field-theoretical approach, there exist electric field vortices then they will not only form the elementary particles in the vacuum, but will also macroscopically form and have an effect in larger dimensions.
Assuming a wave that rolls up to a plane vortex it would be obvious if polarization and velocity of propagation are conserved in the process. But how does it stand about the
frequency? The wave now will walk round a stationary point, the vortex centre. The propagation with
the speed of light c will remain existent as the swirl velocity. For a plane circular vortex, where the path for a revolution on the outside is very much longer than near the vortex
centre, there arises a longer wave length and as a consequence a lower frequency on the outside as more to the inside. With this property the vortex proves to be a changer of
frequency: the vortex transforms the frequency of the causing wave in an evenly spectrum, that starts at low frequencies and stretches to very high frequencies (fig. 1.4). Exactly this property we observe in "white noise". The consistent conclusion would be
that this concerns the vortex of the electric field. Anyone can, without big expenses, convince himself or herself of the localization, of the property to change the frequency and
of the circumstance that vortices can be very easily influenced, that they avoid or again whirl about a place of disturbance, for instance an antenna. For that one only needs to tune
a radio receiver to a weak and noisy station and move oneself or some objects around, then one is able to directly study the influences from the manipulation of the receiving
signal.
But already the fact that the using and measurability of signals is limited by noise makes clear. which attention the potential vortex should be given.
Within a limited frequency range the power of the Nyquist or resistance noise is independent of frequency (fig. 4.7). This should be clarified particularly by the term "white noise" analogous to white light, where all visible spectral ranges independent of frequency have the same energy density.
But this relation doesn't hold for high frequencies of any magnitude. Here another noise- effect appears, that is said to have its cause in the quantum structure of energy . Untouched by possible interpretations an increasing power of the noise is measured, that more and more turns into a being proportional to frequency (fig. 4.7, curve a). Interestingly this curve shows a remarkable duality to the power curve of eddy currents, likewise shown against the frequency, that for instance can be measured at eddy current couplings (fig. 4.7, curve b). This circumstance suggests a dual relation of the potential vortex of the electric field in bad conducting media on the one hand and the eddy current in inductive materials on the other hand .
EMC Journal 1/95, 6. J, ISSN 0945-3857, S. 56 - 59. 66
capacitor losses
a) measurement set up according to Yializis and others
Fig. 4.8: Measurement set up (a) and photo of vortex structure in a metallized polypropylen layer capacitor (at 450 V/ 60 Hz/ 100°C)
Observation of the formation of a vortex (b) and (c). (110 fold magnification), according to Yializis et al.
Polypropylene Capacitors, Proceedings of IEEE, International Symposium on Electrical Insulation, Bosten, Mass., June 1980;
properties ______________________________________________________________________________ 67
4.8 Capacitor losses Next the dielectric losses in a capacitor fed with an alternating voltage are measured and likewise put on against the frequency. At first the course is independent of the frequency, but towards higher frequencies it increases and shows the same characteristic course of the curve as the before mentioned power of the noise (fig. 4.7, curve a).
This excellent agreement suggests the assumption that the dielectric losses are nothing but eddy losses.
These vortex phenomena, caused by time-varying fields, are not only found in ferro- magnetic and conductive materials, but equally as dual phenomena in dielectrics and non- conductors.
As examples of practical applications the induction welding or the microwave oven can be mentioned. The process can be described in other words as follows: in both examples the
cause is posed by high-frequency alternating fields that are irradiated into a dielectric as an electromagnetic wave, there roll up to potential vortices and eventually decay in the
vortex centre. The desired and used thermal effect arises during this diffusion process. The striving in the direction of the vortex centre gives the potential vortex of the electric
field a structure shaping property. As a consequence of this "concentration effect" circular vortex structures are to be expected, comparable to the visible vortices in flow
dynamics (e.g. tornados and whirlwinds). At the same time the dual anti-vortex arises, the diverging eddy current. It takes, as is well-known, the given structure of the conductor, so in the technical literature one correspondingly talks of a "skin effect". Now if conductor and non-conductor meet as they do in a capacitor, then at the boundary
area visible structures will form. Circles would be expected, if the eddy current in the inside and striving to the outside is equally powerful as the potential vortex that comes from the outside and concentrates.
A c t u a l l y such circular structures are observed on the aluminium of high tension capacitors, when they were in operation for a longer period of time. The formation of these circles, the cause of which until now is considered to be unsolved, is already
experimentally investigated and discussed on an international level by scientists (fig. 4.8) .
These circular vortex structures can be seen as a visible proof for the existence of
potential vortices of the electric field. Capacitors, IEEE Transactions on EI-19,August 1984,No.4,pp.288-293.
EMC Journal 1/95, 6.J, ISSN 0945-3857, S. 56-59.
Yüklə 4,22 Mb. Dostları ilə paylaş:
|