Impulse Generator Waveform Generation Using MARX Circuit A

This MATLAB Code will plot the Standard Lightning Impulse Waveform (1.2us/50us) for given circuit parameters: Vm, C1, C2, R1 and R2.

The circuit generates a high-voltage pulse by charging a number of capacitors in parallel, then suddenly connecting them in series. See the circuit diagram on the right. At first, n capacitors (C) are charged in parallel to a voltage VC by a DC power supply through the resistors (RC). The spark gaps used as switches have the voltage VC across them, but the gaps have a breakdown voltage greater than VC, so they all behave as open circuits while the capacitors charge. The last gap isolates the output of the generator from the load; without that gap, the load would prevent the capacitors from charging. To create the output pulse, the first spark gap is caused to break down (triggered); the breakdown effectively shorts the gap, placing the first two capacitors in series, applying a voltage of about 2VC across the second spark gap.[2] Consequently, the second gap breaks down to add the third capacitor to the "stack", and the process continues to sequentially break down all of the gaps. This process of the spark gaps connecting the capacitors in series to create the high voltage is called erection. The last gap connects the output of the series "stack" of capacitors to the load. Ideally, the output voltage will be nVC, the number of capacitors times the charging voltage, but in practice the value is less. Note that none of the charging resistors Rc are subjected to more than the charging voltage even when the capacitors have been erected. The charge available is limited to the charge on the capacitors, so the output is a brief pulse as the capacitors discharge through the load. At some point, the spark gaps stop conducting, and the low-voltage supply begins charging the capacitors again.

Run the MATLAB Code with following data:

Enter wave front resistor, R1 on IG side = 420

Enter wave tail resistance, R2 = 2981

Enter capacitance of the impulse generator, C1 = 0.01u-6

Enter capacitance of the impulse generator, C1 = 0.02e-6

Enter capacitance of the test object, C2 = 0.001e-6

Enter the charging voltage of impulse generator, Vin = 120e3