• Title/Summary/Keyword: Body force density

Search Result 3, Processing Time 0.114 seconds

Evaluation of Global Force and Interaction Body Force Density in Permanent Magnet Employing Virtual Air-gap Concept (가상공극개념을 이용한 연구자석의 전체전자기력과 상호체적력밀도 계산)

  • Lee, Se-Hee
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.58 no.2
    • /
    • pp.278-284
    • /
    • 2009
  • The global force and interaction body force density were evaluated in permanent magnets by using the virtual air-gap scheme incorporating the finite-element method. Until now, the virtual air-gap concept has been successfully applied to calculate a contact force and a body force density in soft magnetic materials. These force calculating methods have been called as generalized methods such as the generalized magnetic charge force density method, the generalized magnetizing current force density method, and the generalized Kelvin force density method. For permanent magnets, however, there have been few research works on a contact force and a force density field. Unlike the conventional force calculating methods resulting in surface force densities, the generalized methods are novel methods of evaluating body force density. These generalized methods yield the actual total force, but their distributions have an irregularity, which seems to be random distributions of body force density. Inside permanent magnets, however, a smooth pattern was obtained in the interaction body force density, which represents the interacting force field among magnetic materials. To evaluate the interaction body force density, the intrinsic force density should be withdrawn from the total force density. Several analysis models with permanent magnets were tested to verify the proposed methods evaluating the interaction body force density and the contact force, in which the permanent magnet contacts with a soft magnetic material.

On the Physical Meaning of Maxwell Stress Tensor (맥스웰 응력텐서의 물리적 의미의 고찰)

  • Choi, Hong-Soon;Park, Il-Han;Moon, Won-Kyu
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.58 no.4
    • /
    • pp.725-734
    • /
    • 2009
  • Maxwell stress tensor is one of the methods which are generally used for electromagnetic force calculation. In this paper, it is presented that Maxwell stress tensor T and n${\cdot}$T have no physical meaning and therefore should not be used as sources of mechanical force for deformations or dynamics. The divergence of Maxwell stress tensor ${\nabla}{\cdot}T$ is the one which can acquire a physical identity and is electromagnetic body force density by an action at a distance like a gravity. This result can be derived from the principle of power balance, and also verified by some thought experiments. The virtual air-gap approach is proposed as a valid solution for the calculation of the body force.

An Observation of Unified Force Expression in The Cylindrical Magnetic Material with a Vertical Current Running Through Its Center (전류가 관통하는 원통형 자성체에 미치는 전자기력식의 통일성에 대한 고찰)

  • Choi, Hong-Soon
    • Journal of the Korean Magnetics Society
    • /
    • v.21 no.5
    • /
    • pp.174-179
    • /
    • 2011
  • Magnetic force calculation methods such as Maxwell stress, virtual work principle, equivalent magnetic charge, and equivalent magnetizing current are widely used until now. The force density is still controversial issue even though it is common sense that all of these methods have legitimate results. The surface force densities of each method are quite different with each other in the point of numerical result and final expression. In this paper, it is shown that a unified expression of body force density is derived using virtual air-gap scheme for an analytic model in which cylindrical magnetic material with a vertical current runs through its center.