Técnicas de atenuação da ocorrência e dos efeitos dos transitórios de tensão em motores de indução t

artigo tĂŠcnico Fernando E. Ferreira(1)(2), Carlos A. SĂĄ(3), Joaquim F. S. Carvalho(1)

TÊcnicas de Atenuação da Ocorrência e dos Efeitos dos Transitórios de Tensão em Motores de Indução Trifåsicos de Baixa Tensão

Resumo

O sistema de isolamento dos motores de indução de baixa tensão estå sujeito

Palavras Chave: Motores de Indução, Variadores Electrónicos de Velocidade, Sistema de Isolamento, Transitórios de Tensão, Descargas Parciais, Manutenção Curativa de Motores ElÊctricos.

Siglas

a vĂĄrios mecanismos de desgaste de

DE

Descarga ElĂŠctrica

natureza elĂŠctrica, tĂŠrmica, quĂ­mica e

DP

Descarga ElĂŠctrica Parcial

mecânica que, individualmente ou em

MI

Motor de Indução

MIV

MI alimentado por VEV

PWM

Modulação por Largura de Impulso

conjunto, conduzem à sua degradação e à ocorrência de diversos modos de

RD

Rigidez DielĂŠctrica

avaria. Neste artigo abordam-se as

SI

Sistema de Isolamento ElĂŠctrico

causas e os efeitos dos transitĂłrios de

TD

TensĂŁo Disruptiva

TT

TransitĂłrio de TensĂŁo

TVT

Taxa de Variação da Tensão

tensão nos motores de indução de baixa tensão, com particular destaque

VEV

Variador ElectrĂłnico de Velocidade (com VSI e PWM)

para os que são alimentados por inversores por fonte de tensão com modulação por largura de impulso,

VSI

Inversor por Fonte de TensĂŁo

I. Introdução

e discutem-se algumas tÊcnicas para a sua atenuação.

(1)

Instituto Superior de Engenharia de Coimbra Instituto de Sistemas e RobĂłtica de Coimbra (3) Faculdade de Engenharia da Universidade do Porto (2)

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Na indústria da União Europeia, cerca de 90% dos sistemas elÊctricos de força motriz incorporam motores indução trifåsicos com rotor em gaiola de esquilo (MIs) [1].

Mais recentemente, a alimentação dos MIs com variadores electrónicos de velocidade permitiu a sua

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artigo tĂŠcnico [6]Kemp, I.: Partial Discharges in Solid Insulation, Colloquium on Advances in HV Technology (Digest No. 1996/173), IEE, 1996; [7]Lebey, T.: Influence of some voltage waveform characteristics on the partial discharge patterns: application to PWM power supply, Proceedings of the Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference, October 1999; [8]Dymond, J.; Stranges, N.; Younsi, K.: Stator Winding Failures: Contamination, Surface Discharge Tracking, Transactions on Industry Applications, IEEE, Vol. 38, Issue: 2, March-April 2002; [9]Campbell, S.; Stone, G.: Examples of Stator Winding Partial Discharge due to Inverter Drives, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation, Anaheim, USA, April 2000; [10]MĂźller, K., et al.: An Approach for Measuring Partial Discharges in PWM Inverter Driven Induction Machines, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation, Anaheim, USA, April 2000; [11]Neacsu, C.; Bidan, P.; Lebey, T.: Off Line Measurements of Partial Discharges in Turn Insulation of Low Voltage Rotating Machines, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation, Anaheim, USA, April 2000; [12]Casale, M.; Schifani, R.: Partial Discharge Tests Using CIGRE Method II, IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 7, No. 1, February 2000; [13]Watson, J.: The Use of Line Current as a Condition Monitoring Tool for Three Phase Induction Motors, IEE, Savoy Place, London, 1999; [14]Stone, G., et al.: New Tools to Determine the Vulnerability of Stator Windings to Voltage Surges from IFDs, Electric Machines and Drives, International Conference IEMD ‘99, May 1999; [15]Beeckman, R., et al.: Studies on Magnet Wire Degradation with Inverter Driven Motors, Proceedings of the Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference, 1997; [16]Kaufhold, M., et al.: Electrical Stress and Failure Mechanism of the Winding Insulation in PWMInverter-Fed Low-Voltage Induction Motors, IEEE Transactions on Industrial Electronics, Vol. 47, No. 2, April 2000; [17]Gao, G., et al.: Studies on the Insulation Life of Adjustable Speed Drive (ASD)-fed Motors Under Accelerated Aging Conditions, Conference on Electrical Insulation and Dielectric Phenomena, 1999; [18]Cavallini, A., et al.: Voltage Endurance of Elec-

trical Components Supplied by Distorted Voltage Waveforms, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation, Anaheim, USA, April 2000; [19]Jackson, D.: Low Voltage Insulation System Endurance Against Electronic Waveform and Cable Length, Colloquium on Effects of High Speed Switching on Motors and Drives (Ref. No. 1999/144), IEE, June 1999; [20]Schump, D.: Winding Tests for “Drive Duty� Induction Motor Stators, Proceedings of the Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference, October 1999; [21]Stone, G., et al.: Methods to Determine which Inverter Drives need Upgraded Motor Stator Windings, Pulp and Paper Industry Technical Conference, Conference Record, June 2000; [22]Baker Instrument Company: Measure of Quality, 2001; [23]Penrose, H.: Repair Specification for Low Voltage Polyphase Induction Motors Intended for PWM Inverter Application, 2nd Edition, Book 2 of the MotorDocTMSeries, 2001; [24]Penrose, H.: Variable Frequency Drives Theory, Application, and Troubleshooting, University of Illinois at Chicago, Energy Resource Center, 2001; [25]Jackson, D.: Reliability Through Increased Safety Insulation Systems – The effect on high-speed switching on the motor insulation system, Power Engineering Journal, August 2000; [26]Steinke, J.: Use of an LC Filter to Achieve a Motorfriendly Performance of the PWM Voltage Source Inverter, IEEE Transactions on Energy Conversion, Vol. 14, No. 3, Sept. 1999; [27]Habetler, T. et al.: Design and Implementation of an Inverter Output LC Filter Used for dV/dt Reduction, IEEE 1999; [28]Beeckman, R.: Inverter Drive Issues and Magnet Wire Responses, Proceedings of the Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference, October 1999; [29]Wood, S.: The Design of Large Machines for Variable Speed Drives, IEE, Savoy Place, London, 1999; [30]Leeson Electric Corporation: LEESON´s IRISTM – Inverter Rated Insulation System, 2002; [31]Al-Ghubari, F.; Jouanne, A.; Wallace, A.: The Effects of PWM Inverters on the Winding Voltage Distribution in Induction Motors, Electric Power Components and Systems, July 2001; [32]Oyegoke, B: Voltage Distribution in the Stator Winding of an Induction Motor following a Voltage Surge, Electrical Engineering Research Journal, Vol. 82, No. 3-4, March 2000.

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