29th Symposium on Fusion Technology (SOFT 2016)

P4.013 Fault energy dump & repeated breakdown validations of HVPS commissioned for negative ion source-ROBIN

8 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 13

Poster A. Experimental Fusion Devices and Supporting Facilities P4 Poster session

Speaker

Mahesh Vuppugalla (Institute for Plasma Research)

Description

Successful operation of a Neutral Beam Injector is dependent on the performance of High voltage power supply system(HVPS) for the production of ion beam. To meet the functional requirements of ion extraction, the power supplies(PS) are designed for fast output cut-off, low energy content during breakdown(BD), ability to withstand repeated BD. It is important that features of the PS are validated in a manner that ensures their integration with ion source.  For negative ion source ROBIN, the HVPS consists of two DC PS, namely extraction power supply system(EPSS:-11kV,35A) for the extraction of negative ions, which floats over Acceleration power supply system(APSS:-35kV,15A) for the acceleration of negative ion beam. The following special attributes of the PS and their qualification procedure have been carried out, prior to their integration with ROBIN: a)Energy storage-The PS have been designed with fast output cut-off(<10μs) to ensure the energy dump during BD is <10J to avoid damage to the grids of the ROBIN. A wire test has validated this critical feature; b)BD and subsequent reapplication of HV for 200 times-The test for the repeated BD has been carried out on each power supply individually and also with EPSS floating over APSS, upto 200 times with 15ms HV inhibition between BD. The peak current observed during BD is ~250A. A passive BD protection scheme has been implemented to further reduce the peak current during BD. While conducting these tests, critical technical issues like voltage shoot-up across EPSS during BD in APSS, noise interferences during BD etc. were encountered which seriously affected the performance of the PS. These issues were resolved after investigating their causes and implementing the appropriate solution. The paper will highlight about testing methodology for validation of fault energy dump and repeated BDs, passive BD protection scheme and issues encountered during testing & their resolution.