Numerical Approach for Computation of Electromagnetic Shielding

Mayer, Daniel; Ulrych, B.

doi:10.2478/jee-2013-0037

Cited by 4 publications

(4 citation statements)

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“…The magnitude of the magnetic force F M , the Maxwell’s pulling force, acting between the yoke, core and the outer annulus is according to Mayer and Ulrych (2009): …”

Section: Magnetic Force Due To the Magnetic Stiffnessmentioning

confidence: 99%

“…M m is the PM magnetisation. The magnetic induction B ( t ) in the air gap of width d ( t ) is then given: where μ 0 is the permeability of air (vacuum) and d M is the length of magnetic flux line in the ferromagnetic material reduced to air (vacuum), for this particular case defined as: The magnitude of the magnetic force F M , the Maxwell’s pulling force, acting between the yoke, core and the outer annulus is according to Mayer and Ulrych (2009): The magnetic pull is balanced by the elastic elongation of the spring. In the absence of vibrations the static air gap width is d 0 .…”

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confidence: 99%

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Ferromagnetic eddy current damper of beam transversal vibrations

Stein

Tobolka

Chmúrny

2016

Journal of Vibration and Control

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The paper deals with attenuation of transversal vibrations of a clamped-clamped beam loaded by a rigid mass at beam mid-point and excited by vertical force acting at beam mid-point. The novelty of treated approach is the use of a ferromagnetic conductor as the principal damping device. This is a different approach from that one used in contemporary research papers. Beyond vibration attenuation a concurrent shift in damped natural frequency due to the negative stiffness is observable. The theoretical results are complemented by measurements on a test stand. Up to 10 dB attenuation of the most marked resonance peak and frequency shift by up to 5 % to lower frequency was observed.

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“…The magnitude of the magnetic force F M , the Maxwell’s pulling force, acting between the yoke, core and the outer annulus is according to Mayer and Ulrych (2009): …”

Section: Magnetic Force Due To the Magnetic Stiffnessmentioning

confidence: 99%

mentioning

confidence: 99%

Ferromagnetic eddy current damper of beam transversal vibrations

Stein

Tobolka

Chmúrny

2016

Journal of Vibration and Control

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“…With respect to a relatively low frequency, the skin effect in these conductors may be neglected. This field can be expressed in terms of the magnetic vector potential A, whose distribution is described by the equation (see [3], [4]) curl 1…”

Section: Electromagnetic Field In the Feeding Conductorsmentioning

confidence: 99%

Heating of Three-Phase Shielded Supply at Short Circuit

Mayer¹,

Ulrych²,

Kropík³

2015

AEI

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Following the calculation of the mechanical forces acting on the shielded three-phase line published in [1] and [2], an algorithm describing numerical calculation of its temperature rise due to short-circuit currents is presented. Given are the equation for determining the electromagnetic sources of heating, heat transfer equation for propagation of heat in the line and another equation for a simplified calculation of the temperature rise of the line provided that the investigated temperature process is adiabatic. The methodology is illustrated with a typical example.Keywords: shielded three-phase line, three-phase short circuit, heating of three-phase line FORMULATION OF PROBLEMFeeding lines of high-power electrical rotating machines, transformers, arc furnaces and many other devices are highly stressed mechanically and thermally, in particular at short circuit. Mechanical stresses on these conductors can significantly be reduced using wires shielded with steel jackets, see [1] and [2]. On the other hand, the presence of shielding complicates local thermal situation; it reduces the possibility of transfer of heat from the conductor and, moreover, further losses by eddy currents induced in the shielding jackets are generated, representing additional sources of heat. The paper describes a method for calculation of heating of such a shielded conductor. The paper supplements the above works, as it describes the method of calculation of temperature rise of feeding lines. The results allow carrying out such a design of the line that is safe with respect to the thermal damage of its insulation. Consider a three-phase line represented by straight conductors X, Y, Z. The conductors can be either massive or created by electrically conductive ropes that are insulated and placed in the shielding steel jackets, see Fig. 1. The conductors are supposed to carry short-circuit currents. The aim of the paper is to investigate the volumetric Joule losses in the wires and shielding jackets and formulate an algorithm for calculation of their heating. Since the fault is a short phenomenon, the process of heating will be assumed adiabatic, i.e., heat is not transferred to the neighbourhood of the conductors. This assumption leads to higher temperatures than those actually occurring in the system. As information about heating serves for evaluating heat stress of the insulation system of the feeding line, the method provides safer values.The short-circuit currents in the conductors X, Y, Z are expressed by the following formulae:where A, B, C, T A , and T D are the parameters of the shortcircuit current. MATHEMATICAL MODELThe task can be solved with a sufficient accuracy as a weakly coupled electromagnetic-thermal problem. The electromagnetic phenomena are not tightly connected with the thermal effects and may be solved separately. Electromagnetic field in the feeding conductorsThe field in the conductors is quasistationary. With respect to a relatively low frequency, the skin effect in these conductors may be neglected. This f...

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“…in heads of turbo-alternators winding, outlets of large rotating machines or power transformers, inlets of arc furnaces, etc. These forces can be restricted by shielding [1]. However, improperly made shielding can reduce the forces only insufficiently, or it can cause excessive eddy currents losses in shielding jacket followed by heating, or it can cause insufficient heat conduction by cooling medium.…”

Section: Introductionmentioning

confidence: 99%

Forces Acting on the Shielded Three-Phase Supply

Mayer¹,

Ulrych²,

Polcar

2014

AEI

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Mechanical forces impact three-phase line conducted by large currents. These forces cause higher safety requirements. This paper deals with possibilities of lowering these forces by shielding of the conductors. The numerical method of calculation of the time function of forces, when conductors are shielded by ferromagnetic jackets and conducted by symmetrical three-phase system currents, is stated. The calculation of eddy currents density induced into shielding jackets is stated further; eddy currents cause the heating of shielding jackets. An illustrative example shows that properly designed shielding is able to strongly reduce the magnitude of forces while the eddy current losses density is very low is the heating is subtle.

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Numerical Approach for Computation of Electromagnetic Shielding

Cited by 4 publications

References 1 publication

Ferromagnetic eddy current damper of beam transversal vibrations

Ferromagnetic eddy current damper of beam transversal vibrations

Heating of Three-Phase Shielded Supply at Short Circuit

Forces Acting on the Shielded Three-Phase Supply

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