Influence of System Parameters Using Fuse Protection of Regenerative DC Drives 4
Influence of System Parameters Using Fuse Protection of Regenerative DC Drives
By
Dr. Hedaya Mahmood Alasooly
Hedaya_alasooly@yahoo.com
While every precaution has been taken in the preparation of this book, the publisher assumes no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.
Influence of System Parameters Using Fuse Protection of Regenerative DC Drives
Copyright © 2021 Dr. Hedaya Mahmood Alasooly.
Written by Dr. Hedaya Mahmood Alasooly.
Note: This eBook is a guide and serves as an initial guide. As a person affected, it is advisable to additionally seek professional advice .
1. Introduction:
1. Introduction:
Current-limiting fuses are widely used to protect the thyristors in dc drive systems. In the event of the commutation failure when regenerating (inverting), the fuses need to interrupt in loop supplied by the ac and dc voltages acting in series which is the most difficult case for protection by fuse.
In this paper, a detailed study of the complete interruption process has been investigated by modeling of arcing process of the fuse. The effect varying the motor time constant, supply impedance, number of fuses used to clear the fault and dc machine rating to the total response for fuses protecting against the regenerative circuit internal commutation fault has been studied. The model of 200A fuse is employed in this study and fuses in series with the semiconductor devices (F1) and fuses in ac line (F2) are both considered.
2. The main model used in the study:
2. The main model used in the study:
The basic function of the phase-controlled converter is to convert an alternating input voltage to controllable direct output voltage. The 2-qudrant converter consists basically of a conventional rectifier circuit arrangement which contains thyristors. Due to the unidirectional current carrying property of the thyristors, the current at dc terminal can flow only in one direction. However, it is possible by suitable control of the phase position of the firing pulses applied to the thyristors with respect to ac input voltage, for the mean voltage at dc terminals to be continuously controlled from maximum positive to maximum negative. Thus power can flow either from ac to dc side of the converter, and vice versa, and the converter is capable to work as an inverter or rectifier.
The average output voltage is given by 
. When 0<α< 90, 
positive (rectifier mode), while when 90<α< 180, 
negative (inverter mode). If the 2-quadrant converter is connected to the armature of a dc machine, the polarity of the induced emf of the machine reverses whenever regenerative breaking is required. For example, when the load is being raised, the converter supplies power to machine and induced emf is positive. On the other hand, when the load lowered, the direction of rotation and induced emf are reversed. Therefore, the polarity of the machine emf is now negative. Consequently, it is in the correct direction for the converter to operate in its inverter region, returning power from machine to ac system.
Internal commutation fault will occur if a thytristor that has being conducting fails to turn off. Alternatively, this fault
Impressum
Verlag: BookRix GmbH & Co. KG
Tag der Veröffentlichung: 17.05.2021
ISBN: 978-3-7487-8308-4
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Widmung:
Note: This eBook is a guide and serves as an initial guide. As a person affected, it is advisable to additionally seek professional advice .