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Overvoltages Caused By Step-up Transformer and Long Cables in Medium Voltage Inverter Drives
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| Author(s) |
J. Pontt; E. Perelli; J. Rodriguez; S. Fuentes; B. González; L. Sanhueza; I. Quezada |
| Abstract |
Failure of the winding isolation of two 13.8 kV three-phase induction motor fan drives fed by a PWM medium voltage inverter through a step-up transformer and cables longer than 400 meters motivated this study. Each motor drives a fan for air-ventilation of an underground copper mine at Codelco El Teniente, Chile. The isolation failure suggested that overvoltages values higher than expected were generated. In order to the better understanding of the phenomena, a modelling and simulation for the analysis of the harmonic motor overvoltages caused by step-up transformers and long cables in a medium voltage inverter drive was carried on. The simulation results confirmed that the natural resonant modes of the electric system feeding the motor terminals can be excited by the harmonic voltages applied by the PWM inverter. The solution proposed by the vendor was the application of a damping low pass filter between the inverter and step-up transformer. The study verified that the proposed filter helps to reduce the voltage stressing of the motor winding isolation. Because another similar fan-drive application were at the setting-up, a direct measurement of the motor terminal voltages was agreed in order to verify the overvoltages generation and proper isolation coordination with the motor windings. The measurements, made with broad range frequency capacitive transducers and a high-voltage probe, confirmed the predictions given by the modeling and simulation study. |
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| Filename: | EPE1999 - PP00500 - Pontt.pdf |
| Filesize: | 533.9 KB |
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| Type |
Members Only |
| Date |
Last modified 2004-04-08 by System |
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