Commissioning and Initial Operational Experience of 2 MVA AC/DC Power Converter at IPR for Neutral Beam Injector Applications

At the Institute for Plasma Research (IPR), Gandhinagar a 2 MVA ac/dc accelerator power supply (APS) unit was installed for powering the neutral beam injector (NBI) to be used in Nuclear Fusion Power Research. The APS is based on a 12-pulse converter system consisting of a 1.914 MVA, 11 000/541.86/541.86 V converter transformer and two six-pulse rectifiers connected in parallel. The unit feeds 3 nos. high frequency inverters (400 Hz) which are connected to high voltage rectifier-transformers (HVTRU) producing high voltage dc at the output. First, the converter transformer and the rectifier were successfully installed at IPR in September 2020. Precommissioning tests of the transformer were carried out at site which included the measurement of winding and insulation resistances (IRs), magnetic balance test, vector group test, voltage ratio check, magnetizing current measurement, and oil BDV test. The results were found to be satisfactory and the transformer was energized at no-load. Then the complete power supply was tested at no-load and on-load with a dummy load bank arranged at IPR. A heat run test for continuous 8 h was also carried out with load bank and the temperature rise was found to be within limits. All functions of the power supply and associated controls and interlocks were commissioned successfully. The site acceptance tests verified the ruggedness of the system along with the specified technical requirements. This article also discusses the initial operational experience of the system which includes the connection of reactive power compensator and harmonic filter (RPC and HF) which was readily available at site and occurrence of a major fault at 11 kV isolator panel. Though the RPC and HF improved the supply power factor (PF), the current distortion marginally increased.