DESIGN OF THE NEPTUNE NODE CONVERTER Vatché Vorpérian Jet Propulsion Laboratory

Contents 1.Converter Specifications 2.Converter Design and Block Diagram 3.Schematics and theory of operation 4.Simulation result

1.0 Converter Specifications (Rev 1.0) 1.1 Switching frequency 1.2 Input Specifications 1.3 Output Specifications 1.4 Efficiency 1.5 Environmental Specifications

1.1 Switching frequency Fixed frequency 50kHz 1%. Control parameter: pulse width modulation (PWM). Converter type: series parallel combination of isolated two-switch forward converter (buck derived topology)

1.2 Input Specifications Input bus voltage: a) Converter turn on and turn off: When the bus voltage exceeds 5.7kV, a vacuum switch relay is closed and the converter is turned on as the bus voltage is applied to the input of the converter. When the bus voltage drops below 5.1kV, the vacuum switch relay is opened and the converter is disconnected from the bus

b) Input voltage range for normal operation After the converter is turned on, it will meet all input and output specifications for an input bus voltage range of 5.1kV < < 10kV. c) Input overvoltage condition The converter will survive without any damage for an input overvoltage of up to 15kV indefinitely. Not all specifications will be met under this condition

d) Input undervoltage condition The converter shall survive indefinitely any undervoltage condition on the input bus voltage less than 5.1kV Input ripple current The maximum peal-to-peak ripple current generated by the converter shall not exceed 1.5mA peak-to-peak at 50kHz. This maximum occurs when the bus voltage is at its minimum of 5.2kV

1.2.3 Inrush current The maximum inrush current shall not exceed 7.0A The maximum inrush current occurs when the vacuum relay switch is closed while a) the shore generator voltage is at 10kV and b) the converter is separated from the shore generator by 100km of backbone cable with the following parameters: 1mH/km, 0.2uF/km and 1 Ohm / km

1.2.4Steady-state input current The maximum steady state input current shall not exceed 2.15A. This occurs at maximum output power (10kW) and minimum input bus voltage (5.1kV) Transient response of input current to dynamic load change TBD

1.3 Output specifications 1.3.1Output voltage and regulation The dc output voltage is 400V (+/-) 1% for 0-25A load current and 5.1kV-10kV input voltage 1.3.2Output current The output current is rated at 25A.

1.3.3Output voltage and switching ripple and spikes The maximum peak-to-peak output voltage switching ripple at 50kHz is 1.3V which occurs at maximum input voltage of 10kV The maximum peak-to-peak spikes of about 50 nsec duration and 50kHz periodicity shall not exceed 10V when measured at the output of the converter with a bandwidth of 100MHz

1.3.2 Dynamic load response of output voltage Step load change 10% to 50%: undershoot TBDsettling time TBD Step load change 50% to 10%: overshoot TBDsettling time TBD Step load change 50% to 100% undershoot TBDsettling time TBD Step load change 100% to 50%: overshoot TBDsettling time TBD Step load change 10% to 100%: undershoot TBD settling time TBD Step load change 100% to 10%: overshoot TBDsettling time TBD

1.3.3Output voltage rise time The maximum output voltage rise time is TBD The minimum output voltage rise time is TBD 1.3.4Output overcurrent protection The output current limit is set at 28A. If the converter output current exceeds 28A, it will enter a pulse mode with period TBD

1.3.5Output short-circuit protection If a short circuit on the output of the converter is cleared within TBD msec, the converter output voltage will come up to 400V with a rise time TBDmsec. If the short circuit is not cleared within TBD msec, the converter will enter into a pulse mode with a period of TBD seconds until further action is taken. 1.4Efficiency The efficiency characteristics TBD. At full load the the efficiency is 92-94%.

2.0 Converter block diagram and design

3.0 Schematics

4.0 Simulation results