Existence of partial discharges in low-voltage induction machines supplied by PWM drives

1996 ◽  
Vol 3 (4) ◽  
pp. 554-560 ◽  
Author(s):  
A. Mbaye ◽  
F. Grigorescu ◽  
T. Lebey ◽  
Bui Ai
Keyword(s):  
Low Voltage ◽  
Induction Machines ◽  
Partial Discharges

scholarly journals Extended Use for the Frequency Response Analysis: Switching Impulse Voltage Based Preliminary Diagnosis of Potential Sources of Partial Discharges in Transformer

2020 ◽  
Vol 10 (22) ◽  
pp. 8283
Author(s):  
Kamalaselvan Arunachalam ◽  
Balasubramanian Madanmohan ◽  
Rajesh Rajamani ◽  
Natarajan Prabaharan ◽  
Hassan Haes Alhelou ◽  
...  
Keyword(s):  
Frequency Response ◽  
Low Voltage ◽  
Partial Discharges ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Potential Sources ◽  
Impulse Voltage ◽  
Before And After ◽  
Test Voltage ◽  
Low Capacitance

The Frequency Response Analysis approach (FRA) is useful in the fault diagnosis of transformers. However, its usefulness in diagnosing any potential sources of Partial Discharge (PD) in transformers has not been thoroughly investigated so far. In this work, the use of Impulse voltage-based FRA (IFRA) in diagnosing inter-turn shorts and potential sources of PD were investigated on a 315 kVA, 11 kV/433 V transformer. Inter-turn shorts and PD sources were emulated and the usefulness of IFRA in their diagnosis was investigated while using switching impulse voltage at different magnitude levels as the test signals. For emulating the inter-turn shorts and the PDs, special tappings were provided on one of the 11 kV windings through the low capacitance bushings. Low voltage impulse was successful in diagnosing the inter-turn shorts, but unsuccessful in identifying the sources of PDs. During the test condition, the test voltage was adjusted with the presence of artificially created PD sources. The frequency response of the transformer before and after the inception of PD was observed and analyzed in this article. The FRA results demonstrated that the switching impulse voltage based IFRA approach at moderate voltages could be useful in diagnosing the presence of the potential sources of PDs.

A New Concept for Online Surge Testing for the Detection of Winding Insulation Deterioration in Low-Voltage Induction Machines

2011 ◽  
Vol 47 (5) ◽  
pp. 2051-2058 ◽  
Author(s):  
Stefan Grubic ◽  
Jose Restrepo ◽  
Jose M. Aller ◽  
Bin Lu ◽  
Thomas G. Habetler
Keyword(s):  
Preventive Maintenance ◽  
Online Monitoring ◽  
Low Voltage ◽  
Induction Machines ◽  
Electrical Machine ◽  
Insulation System ◽  
Monitoring Method ◽  
New Concepts ◽  
Turn Insulation ◽  
Winding Insulation

A breakdown of the electrical insulation system causes catastrophic failure of the electrical machine and brings large process downtime losses. Preventive maintenance and online monitoring are some of the methods to improve the reliability and to reduce unscheduled downtime. One of the main reasons for the failure of the machine is the breakdown of the stator turn insulation. The offline surge test is the most commonly used offline test to assess the condition of the turn insulation. There is no online monitoring method that is applicable to low-voltage machines and has the same capabilities as the surge test. This paper introduces new concepts to implement an online surge test. The possibilities and limitations of the online surge test are presented, as well as the simulation and experimental results, to validate the concepts.

scholarly journals Partial Discharges in Insulating Systems of Low Voltage Electric Motors Fed by Power Electronics—Twisted-Pair Samples Evaluation

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 768 ◽  
Author(s):  
Marek Florkowski ◽  
Barbara Florkowska ◽  
Pawel Zydron
Keyword(s):  
Electric Field ◽  
Power Electronics ◽  
Low Voltage ◽  
Partial Discharges ◽  
Mutual Position ◽  
Electric Motors ◽  
Dynamic Activity ◽  
Twisted Pair ◽  
Common System ◽  
Different Diameters

Power electronics switching devices currently represent the dominant technology for supplying low voltage (LV) electric motors. The fast switching processes exert a different class of stress on dielectric insulating materials than standard sinusoidal excitations. Such stresses result in an increase in the dynamic activity of the working electric field, which in turn lead to an increased likelihood of partial discharges (PD). The stator design of low voltage motor is often in form of random-wound windings, where the magnet wires (copper or aluminum round wires coated with thin layer of insulation) form a common system of coils with not precisely defined mutual position of particular turns, resulting in various turn-to-turn and coil-to-coil voltage distributions. Pulse Width Modulated (PWM) voltage waveforms from modern electronic inverters are characterized by very short rise times and presence of repetitively occurring overvoltages that can significantly stress the insulation of feeding cables and motors. These factors influence the inception and dynamics of PD and processes of space charge accumulation in electrical insulation. In this paper investigations performed on round magnet wire twisted-pair samples representing LV motor random-wound winding elements are presented. Special attention was afforded to the twist configurations, observed breakdown voltage and PD activity. To describe the field conditions for the formation of PD in the turn-to-turn insulation system, the results of numerical simulations of electric field distributions for winding wires with different diameters, modeled using the COMSOL program, were analyzed. PD created in the insulating systems of model twisted-pair systems were registered and analyzed using the phase resolved partial discharge analysis (PRPDA) method.

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