INVESTIGATION OF BEARING CURRENTS IN （调查轴承电流的）.pdfVIP

Electrical and Electronics Engineering: An International Journal (ELELIJ) Vol 2, No 4, November 2013 INVESTIGATION OF BEARING CURRENTS IN DUAL MODE OPERATION OF SYNCHRONOUS MACHINE WITH STATIC EXCITATION SYSTEM 1 2 3 Arun Kumar Datta , Manisha Dubey and Shailendra Jain 1 Central Power Research Institute, Bhopal, India 2,3Maulana Azad National Intitute of Technology, Bhopal, India ABSTRACT Days are gone for rotating exciters. Most of the machines those require field excitation are fed from static excitation system (SES). Static systems are prone to generate shaft voltage thereby causing the flow of bearing currents. This paper has presented a thyristor based SES in 12-pulse configuration. This SES is being applied on the field winding of a synchronous machine installed in a short circuit testing laboratory. This machine is of large capacity and without prime mover. SES along with static frequency converter makes this single machine to operate in dual mode (i.e. motor or generator). Functions of SES under different operational modes have been looked into this paper. Causes of generation of shaft voltage and bearing current in perspective with this machine under static excitation system are the main attraction of this paper. KEYWORDS Synchronous machines, shaft voltage, bearing current, static excitation, parasitic capacitance, electric discharge machining. 1.INTRODUCTION Any synchronous machine, be a motor or generator requires dc power in the rotor winding to magnetise the air gap. Four major options can be exercised to source this dc p