2
\$\begingroup\$

If I have a 10 stage Marx generator with each stage at 2.5kV, when I erect all the stages the last stage's negative terminal will be at 22.5kV with respect to ground.

If I want a voltage measurement of these capacitors what is the best way to do this? I am worried about violating the standoff internal to my differential probes since the probes would all share a common ground on the supply/measurement side.

\$\endgroup\$
  • \$\begingroup\$ What value Line input and C value for each stage? \$\endgroup\$ – Sunnyskyguy EE75 Mar 5 at 22:29
1
\$\begingroup\$

VR37000003005JR500 30MΩ 3.5kV working voltage

IEC 60950-1-07 PCB Pollution Level 1 creepage 4mm/kV > 1kV

schematic

Use ~ 1cm air gap around the body to nearest part or above cellulose or dry wood substrate.

\$\endgroup\$
  • \$\begingroup\$ Thank you I will give this a shot \$\endgroup\$ – MaxwellEE Mar 6 at 18:25
1
\$\begingroup\$

Make e.g. a voltage divider with 30 resistors that rated for 1kV each. When needed, use a capacitor parallel to each resistor to compensate for parasitic capacitance of the resistors. Benefit of using multiple resistors is that a high resistance can easier (lower cost/availability) be achieved and power dissipation is distributed over more resistors.

\$\endgroup\$
1
\$\begingroup\$

For measuring these kinds of high voltages, you might consider using a shielded copper sulphate (\$\text{CuSO}_4\$) solution in a cylinder of perspex as one of the resistors in a resistive voltage divider. You can decide on the divider ratio to use used.

Typically, a hollow perspex cylinder is used with a dilute solution of \$\text{CuSO}_4\$ using de-ionized water. For example, in this case you might use a cylinder that is \$30\:\text{cm}\$ long and \$1\frac14\:\text{cm}\$ in diameter. (Increasing the cross-sectional area improves the non-inductive behavior.) The cylinder design also suppresses the effect of coupling capacitance with the surroundings. Advantages for using a solution of \$\text{CuSO}_4\$ is that it is easy to adjust to the resistance you want for the divider (given some other value you've also chosen for the non-inductive carbon film resistors used in parallel, perhaps, to make up the other resistor of the divider), it can withstand many megavolts across it, and you can make it in a variety of convenient shapes.

Enclose the non-inductive carbon film resistors (use a number of them in parallel for the value you want -- do not use just one by itself) in an aluminum cylinder that extends partway up the outside of the perspex cylinder to provide shielding from EMI for the non-inductive, parallel carbon film resistor group.

Look these up on the web. They are built and used very often for Marx generator voltage measurements in laboratories.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.