Finite element analysis of stiffness characteristics of an electromagnetic device

Abstract

An electromagnetic device, consisting of a pair of permanent magnets and a non-magnetic coil, has shown its linear advantages for inducing parametric stiffness excitation in the laboratory. The electromagnetic device powered by a DC coil current acts like a mechanical spring with constant stiffness. The effects of design parameters upon the electromagnetic stiffness and its linear operating range (referred as the stiffness characteristics) are important and crucial for the design and usage of the device. Thus, a numerical method, based upon the commercial finite element method (FEM) package ANSYS/Emag, was presented for analyzing the stiffness characteristics of the device with DC coil current. The theory foundation for computing the electromagnetic force using FEM was derived and the program realization in ANSYS was introduced briefly. Two typical examples were chosen to verify the accuracy of the numerical analysis method. Based upon these, the restoring force characteristics of the electromagnetic device with various DC coil currents were obtained utilizing the numerical method. Two important indicators (proportional coefficient between linear stiffness and coil current and linear range of the stiffness) were defined for measuring the stiffness characteristics of the electromagnetic device. Then, the effects of the design parameters (both the electromagnetic and structural parameters) on the two indicators were investigated, respectively. The research results provide useful references for the stiffness design of the electromagnetic device in actual practice.

Experimental study on dynamic characteristics of linear parametrically excited system

“…As the electromagnetic stiffness is linearly proportional to the coil current, k e0 is ascertained as k e0 ¼ ffiffiffi 2 p a 0 I 0 , in which I 0 are the RMS values of the current applying to the electromagnetic device, and a 0 is the current/stiffness proportional coefficient. It is shown that a 0 is independent of the coil current and could be obtained by finite element method once the design parameters of the electromagnetic device are given [15].…”

“…The quantitative relationship between the DC coil current and linear electromagnetic stiffness was obtained utilizing the finite element method, and various design parameters of the electromagnetic device were discussed in [15] for their effects upon the current/stiffness relationship and linear stiffness range. Based upon this, the experimental system was designed in the laboratory, and the parametric instability of the cantilever beam under two electromagnetic excitations was studied experimentally and analytically by the authors [16].…”

Detection and Location of Stator Winding Interturn Fault at Different Slots of DFIG

“…The generator is equivalent to an inductance element, and the magnetic field as a medium makes the generator realize the conversion of electromechanical energy [25]. After Maxwell's creative equation of the electromagnetic field was developed, a new theoretical basis for the study and analysis of the electromagnetic field in the generator was provided.…”

A New Method to Extract Substructures for the Multi-Shaft Transmission

“…Considerable progress has been made in the study of gear transmission system in recent years [1]. Generally, dynamic characteristics of gear systems are obtained from many numerical techniques such as Lumped Parameter Method (LPM) [2], transfer matrix method [3][4], Finite Element Method (FEM) [5][6], and dynamic substructure method (DSM) [7][8]. Among them, DSM, which was evolved from the substructure modal synthesis (SMS) presented by Hurty and Gladwell [9] in the early 1960s, has been widely used in solving complex structural dynamic problems in engineering.…”