Detecting partially fallen-out magnetic slot wedges in AC machines based on electrical quantities only

Stojcic, G.; Magnet, Robert; Joksimović, Gojko; Vašak, Mario; Perić, Nedjeljko; Wolbank, T.M.

doi:10.1109/iecon.2012.6389271

Cited by 3 publications

(3 citation statements)

References 6 publications

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“…Stojicic presented in 2011and 2012(Stojicic et al, 2011, 2012 methods to detect missing slot wedges without disassembling. Nevertheless, maintenance is linked with high costs (Lee et al, 2014) and therefore, it is important to know the forces to increase the maintenance interval.…”

Section: Introductionmentioning

confidence: 99%

“…There are forces applied on the wedges, which cause an uncommon behaviour to the slot wedges, resulting in short maintenance intervals. Stojicic presented in 2011and 2012(Stojicic et al, 2011, 2012 methods to detect missing slot wedges without disassembling. Nevertheless, maintenance is linked with high costs (Lee et al, 2014) and therefore, it is important to know the forces to increase the maintenance interval.…”

Section: Introductionmentioning

confidence: 99%

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Damages to magnetic slot wedges in induction machines

Schmülling

Kulig

2015

COMPEL

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Purpose -Magnetic slot wedges are usually installed in open slot high-voltage induction machines. They reduce the no load losses and the magnetization current. Additionally, the leakage inductance increases. However, machines and the slot wedges are getting frequently damaged with a decreasing maintenance interval. The usage of magnetic slot wedges leads to unknown effects. It is possible, that direct magnetic forces or indirect forces, caused by the deformation of the stator or stator teeth during operation, results in the damage of the slots wedges. The purpose of this paper is to fully understand the influence of the magnetic slot wedges and the intrinsic effects. Design/methodology/approach -A finite element model of the affected machine is verified with current and torque values from the data sheet of the affected machine. Three types of forces, which are working on the slot wedges, are considered and compared. Findings -There are direct forces working on the slot wedges. The origin of this forces and a coherence between this forces and the slot number relationship, between stator and rotor slots is shown as well as reasons for the damage to the slot wedges. Originality/value -There are investigations about the influence of the behaviour of an induction machine by magnetic slot wedges. This investigations consider the influence on the network models of such machines. The paper at hand deals with the intrinsic effects caused by the slot wedges and its consequences.(1) the decreasing magnetic air gap leads to a reduction of the no load losses and decreases the magnetization current; and(2) the increasing slot leakage causes decreasing start-up and short-circuit currents.A typical material, used for magnetic wedges in high-voltage induction machines, is MAGNOVAL ® . It has a relative permeability up to m r % 2:9: Table I shows the non-linear magnetic properties of the material, the resistivity κ and its elasticity for mechanical stress analysis.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Damages to magnetic slot wedges in induction machines

Schmülling

Kulig

2015

COMPEL

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“…In addition, in [23] the authors show that the amplitude of the flux density and force waves originating from saturation increase when stator wedges are applied. Furthermore, in [24,25] the detection of fallen out magnetic wedges was studied. A thermal evaluation of the wedges application was performed in [26].…”

Section: Introductionmentioning

confidence: 99%

Application of Wedges for the Reduction of the Space and Time-Dependent Harmonic Content in Squirrel-Cage Induction Motors

Gyftakis

Panagiotou

Kappatou

2013

Journal of Computational Engineering

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The influence of the semimagnetic stator wedges of different sizes on the electromagnetic characteristics and the behavior of the induction motor is investigated. The study will be carried out with both analytical calculations and FEM analysis. The analytical calculations will take into account the stator and rotor slots, as well as the iron core saturation in order to study the spatial and time-dependent harmonic content of the air-gap magnetic flux density and electromagnetic torque. The size of the wedge plays an important role as it determines the tooth tips saturation, the high harmonic content of the air-gap magnetic flux density, and the electromagnetic characteristics of the induction motor.

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Fault detection in magnetic wedges of induction motor

Bossio¹,

Barrera²,

Bossio³

et al. 2015

2015 IEEE 24th International Symposium on Industrial Electronics (ISIE)

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In high power electric motors it is common to use open slots to facilitate the assembly of the coils. Open slots introduce harmonics in the magnetomotive force distribution over the air gap, resulting in additional losses and parasitic torques. In order to reduce these effects, wedges of magnetic material are used. These wedges are prone to apartial or total detachment, which in turn may result in other failures. In this paper a strategy to detect faults in magnetic wedges is presented. This strategy consists of the injection of a zero sequence voltage signal of high frequency. The resulting currents are highly dependent on the magnetic irregularities both the rotor and stator and thus sensitive to asymmetries produced by faults in the wedges. In this way, it is possible to detect and quantify wedges faults without the need to disassemble or remove the IM from the production line. The proposed strategy is applicable offline and required only disconnect the motor of the power supply. Laboratory experimental results are presented to validate the proposal.

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Detecting partially fallen-out magnetic slot wedges in AC machines based on electrical quantities only

Cited by 3 publications

References 6 publications

Damages to magnetic slot wedges in induction machines

Damages to magnetic slot wedges in induction machines

Application of Wedges for the Reduction of the Space and Time-Dependent Harmonic Content in Squirrel-Cage Induction Motors

Fault detection in magnetic wedges of induction motor

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