The following information was submitted:
Transactions: WSEAS TRANSACTIONS ON CIRCUITS AND SYSTEMS
Transactions ID Number: 88-306
Full Name: Miloje Kostic
Position: Doctor (Researcher)
Age: ON
Sex: Male
Address: Koste Glavinica 8a, Belgrade 11000, Serbia
Country: YUGOSLAVIA
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E-mail address: mkostic@ieent.org
Other E-mails: anikolic@ieent.org,nba@ieee.org
Title of the Paper: Negative Consequence of Motor Voltage Asymmetry and Its Influence to the Unefficient Energy Usage
Authors as they appear in the Paper: Miloje Kostic, Aleksandar Nikolic
Email addresses of all the authors: mkostic@ieent.org,anikolic@ieent.org,nba@ieee.org
Number of paper pages: 10
Abstract: Analysis of the effect of unbalanced voltages on the three-phase induction motor is presented in the paper. Since the unbalanced voltage of 2%, 3.5% and 5% increase in losses could reach, in the same order, the amount of 8%, 25% and 50% of nominal power losses in the motor, it is reasonable requirement to permit voltage asymmetry ¡Ü 2%, so this is the upper limit in most national and international standards. The truth is that with a smaller load, the motor could safely work also at higher values of unbalanced voltage. The literature states that the information given previosly is determined from measurements and that they are higher than calculated values. However, it is explained here by the fact that the rotor inverse resistance is higher by 1.4 times compared to the rotor resistance in short circuit mode, since current frequency of the negative sequence in the rotor winding is two times higher (fr,NS ¡Ö 2f1=2fr,SC), i.e. it is higher for 1.41 times than correspon!
ding values given in the literature Thus it is increasingly convinced that the requirements which are given in most appropriate standards are justified. Performed analysis show that there are some considerations that could be included in current standards. Motor operation is not generally allowed when the values of the coefficient of unbalanced voltage are U1,NS/Un ¡Ý 5%, because in the (rare) case when the direct and inverse component of the stator currents in (a) phase matching, increase of the current in that phase would be ¡Ý 1.38 times, and the increase of the losses in the windings of that phase would be ¡Ý 90%.
Keywords: negative sequence voltage, asymetry, power losses, induction motor, energy efficiency, standard
EXTENSION of the file: .pdf
Special (Invited) Session: Motor Voltage Asymmetry Influence to the Efficient Energy Usage
Organizer of the Session: ID646-612
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