High voltage: Can't stop electricity from jumping over resistors

[turgut kalfaoglu]

Hi there. I'm building a 50KV circuit, mainly for the sparks.
I have a ZVS and a cascade to create the volts. To reduce the current, I build a 600k ohm resistor pack - a bunch 100Kohm/5W resistors connected in series.

The whole thing is submerged in oil, but even then, when I turn it on, I can see the sparks jumping over each of the ceramic resistors. The sparks arc over each of the six resistors. I am at a loss as to what else I can try.. I thought these resistors were pretty long so arcing would not happen.

What can I do to prevent arcing?
Many thanks, -tk

 

[Alec_t]

What is the voltage rating of each resistor?

 

[turgut kalfaoglu]

I'm really not sure, it just says 5W100KΩJ on it.. They are 0.89 inch in size.

 

[turgut kalfaoglu]

Btw, I put these resistors at the output of the cascade..

 

[Audioguru]

Name brand resistors have a datasheet that states and guarantees their voltage rating. Resistors made by somebody in their back yard have no guarantee.

 

[turgut kalfaoglu]

Thank you, I'm guessing from your huffy reply that the cause of the arcing is that my resistors are not long enough; they are meant for lower voltages.

 

[Alec_t]

Assuming your 'bunch' is 6, then each resistor will have 50kV/6 = 8.3kV across it. That seems a helluva lot for a 0.89" resistor. Farnell (for example), doesn't list any 100k resistors with a voltage rating >5kV.

 

[duke37]

If you see sparks, then the oil does not have sufficient insulation.
I have had trouble with a sense resistor taking 1mA from a 5kV supply. I used various resistors until I found that some 1MΩ resistors from 1930 were quite happy.
Your application is ten times more severe so to limit the voltage to 1kV per resistor you would need 50 of them. The voltage drop should then be easily accommodated by the oil. There are transfomer oils but I know nothing of these.

 

[(*steve*)]

If using standard resistors, a max of between 200 and 500 volts each would be a reasonable guideline.

So instead of using 6 x 100k resistors, use something like 100 x 6.8k resistors.

 

[Nicholas Schlensky]

You definitely need more resistors or higher voltage ratings. I use slimmox resistors with values of 50k and 1g .these have a voltage rating of 7.5kv or 10kv but are about 25mm long. You will need at least 10 to be sure

 

[Chemelec]

Your Wire Wound resistors have a Very Low Voltage rating.

I have some Dale/Vishay, 100K Resistors that are rated at 7.5 KV that might work better for you.
But you don't say Where you live?