Finite Element Analysis and Experimental Study of the Near-Magnetic Field for Detection of Rotor Faults in Induction Motors

Abstract

Abstract-This paper deals with the finite element analysis and experimental study concerning the influence of the broken bar and rotor dynamic eccentricity faults on the magnetic field outside a squirrel-cage induction motor. The spatial distribution of the magnetic field, the time variation of the magnetic flux density at a point outside the machine and the time variation of the electromotive force delivered by a coil sensor are evaluated based on the finite element models of the healthy and faulty states of the motor. The increase of amplitude from the healthy to the faulty states of some low frequency harmonics measured in the near-magnetic field is emphasized. For broken bar fault, the increase of the amplitudes of specific harmonics of the coil sensor electromotive force, with frequency lower than 25 Hz, is experimentally confirmed.

Dynamic Modelling of Induction Motor Squirrel Cage for Different Shapes of Rotor Deep Bars With Estimation of the Skin Effect

“…I 1 is not known, we impose an arbitrary value (for example 1A), and the rest of the currents will be resolved according to the following equations system in Eq. (11).…”

“…The latter are traversed by an uniform current (without skin effect). It means that the penetration depth of the magnetic field in the aluminium is lower than the radial dimensions of the sub-conductors [11].…”

“…However, those methods only take into account the behaviour of the conductors inside the magnetic circuit. Leaks due to the isthmus of slots are not included, and the resistance and leakage reactance, for the end-bars, and the effect of magnetic saturation are neglected [11,13].…”

“…This is interpreted as two frequency function coefficients depending on the resistance and leakage reactance noted as k r and k x , respectively. The first method is a classical analytical method based on geometric and triangular relations, which offers a good result, verified by many authors as in the case of [7,10,11]. The second is a numerical finite element approach, which takes into account the complexity of the geometric shapes of the bars [9].…”

Calculating an electromechanical torque of a squirrel cage motor based on an axial flux obtained by the FEM

“…This signal is easily measurable and allows to extract many useful information about the condition of the machine itself and about the efficiency of the electric power conversion by this machine [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”