54 ieee power & energy magazine march/april 2016 figure 9. The TNA hardware system. 48-Pulse Inverter Panel Transformer Panels ac-System Emulator Panels 48-Pulse Inverter Board ac System Voltage and Current Measurement Inverter and dc Bus Valve Interface Board Termination Transformer Models Power System Valve Interface Board Digital Interface Board Status Procesor Board Real-Time Control Board Analog Interface Board RS232 Control Cabinet Operator Interface