3.6  Voltage Multiplier

3.6.1  Electrical circuit

Figure 3.26 shows the PSpice schematic of a combination of the IGBT - Switch and the voltage multiplier. The expected output-voltage is:

            n ∙ Uin, peak-peak = 7 ∙ 1300V = 9.1kV.

But the simulation data result is different (Figure 3.27, lower diagram):

Vout,max,1MΩ,4.16kHz = 12.2kV

 

Figure 3.26: PSpice Schematic: Combination of IGBT - Switch and Voltage Multiplier

To determine the optimal configuration, several simulations were made. Figure 3.26 is the result of these simulations. Converted to Protel (layout - program) using the real components, Figure 3.28 and Figure 3.29 were produced. All Diodes are rated for 1200V (RURG501200: hyperfast recovery / 40EPF12: fast recovery). All capacitors are rated for 2kV, manufactured by Arcotronics (type: C4C), suitable for high frequency applications (0.56μF - type: dV/dt = 400V/μs).

 

Figure 3.27: PSpice simulation data: in- and output voltage at the multiplier

In Figure 3.27, the upper diagram shows that the input-voltage at the voltage multiplier has not a rectangular waveform. The spikes caused by the inductor when the current is turned off are increasing the input-voltage. But this effect only exists as long as there is a current flow high enough to generate the spikes at the inductor.

 

Figure 3.28: Protel Schematics: Voltage Multiplier, PCB 1

Because of the large scale of the components the multiplier is divided to three PCBs, one time PCB1 (Figure 3.28 / Figure 3.32) and two times PCB2 (Figure 3.29 / Figure 3.34).

 

Figure 3.29: Protel Schematic: Voltage Multiplier, PCB 2 and 3

Figure 3.30 shows the voltage-level at the capacitors. At C2 and C3 the voltage level of 2kV is exceeded. To achieve sufficient electrical strength at the same capacity, C2 as well as C3 are combined out of four capacitors (cp. Figure 3.25).

 

Figure 3.30: PSpice simulation data: Voltage-levels at the capacitors, R1 = 1MΩ

Figure 3.31 shows the simulated voltage levels at the diodes. The maximum voltage at D1 requires three 1.2kV-diodes in series, the other voltage levels can be blocked by each two 1.2kV-diodes in series.

 

Figure 3.31: PSpice simulation data: voltage-levels at the diodes, R1 = 1MΩ

 

This page is part of a Frameset: Electrodynamic Sculpture: A Thesis by Rafael Bräg.