Fault detection in magnetic wedges of induction motor

Abstract

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.

Efficiency optimization in small induction motors using magnetic slot wedges

“…Although so far it has not been possible to establish the increase of costs for each unit when using magnetic wedges, it could be ensured that it would be below the additional costs other alternatives present (a IE4-class LSPMSM shows costs about 233% higher that a IE2-class SCIM [5]). Unlike open-slot motors, in which there are frequent failures during the mounting process of magnetic wedges due to the electrodynamic stress they undergo [32], in semi-closed slot machines, the geometry of the slot and wedge allows a safer mounting.…”

Research on Non-destructive Intelligence Detection of Tightness of Stator Slot Wedges of Large Hydro-generator

“…G et al injected a high-frequency zero-sequence voltage signal, which highly reflected the magnetic irregularities of the rotor and stator according to the generated current. This method is sensitive to asymmetry caused by wedge faults [7] . In 2018, Wenbin Yu and others provided a fault diagnosis system based on CS-based gap wedge tightness inspection.…”