DC-Bus Electrolytic Capacitor Stress in Adjustable-Speed Drives Under Input Voltage Unbalance and Sag Conditions

This paper analyzes the effects of the input voltage unbalance and sags on the dc-bus electrolytic capacitors in adjustable-speed drives (ASDs) in order to predict their impact on expected capacitor lifetime. The key phenomenon that causes these problems is the transition of the rectifier stage from...

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Bibliographic Details
Published in:IEEE transactions on industry applications 2007-03, Vol.43 (2), p.495-504
Main Authors: Lee, K., Jahns, T.M., Venkataramanan, G., Berkopec, W.E.
Format: Article
Language:English
Subjects:
Adjustable-speed drives
Capacitors
Closed-form solution
Electric potential
electrolytic capacitor stress
Electrolytic capacitors
Exact solutions
Frequency
Impedance
input voltage sag and unbalance
Mathematical analysis
Power capacitors
power quality
Power system harmonics
Rectifiers
Sag
Stress
Temperature
Unbalance
Variable speed drives
Voltage
Voltage fluctuations
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Summary:This paper analyzes the effects of the input voltage unbalance and sags on the dc-bus electrolytic capacitors in adjustable-speed drives (ASDs) in order to predict their impact on expected capacitor lifetime. The key phenomenon that causes these problems is the transition of the rectifier stage from three-phase to single-phase operation. Since the equivalent series resistance increases at low frequencies, the low-order harmonic current components (e.g., 120 and 240 Hz) contribute disproportionately to the capacitor power losses and temperature rise, resulting in reduced lifetime. Closed-form expressions are developed for predicting these effects including the impact of finite line impedance, finite bus capacitance, and varying load. The impact of inverter space-vector pulsewidth-modulation switching on the capacitor loss is also included. Simulations and experimental tests are used to verify the accuracy and effectiveness of the closed-form analysis using a 5-hp ASD system
ISSN:0093-9994
1939-9367
DOI:10.1109/TIA.2006.889910