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Registered Member #1721
Joined: Sat Sept 27 2008, 08:44PM
Location:
Posts: 136
Hello:
I would be greatful if someone could answer two questions I have reference toroids vs spheres as high voltage PS output terminals in DC applications. I understand why toroids are favored in Tesla coils due to capacitance advantages etc. but not why they are favored for DC applications. The two questions I am left with are:
1. Why are toroids favored in very high voltage commercial DC power supplies, when a oblate sphere would be much cheaper to produce?
2. What is the formula to calculate the corona potential of a toroid in air at STP. For example: Say you have a 400KV power supply, what would be the minimum size toroid to prevent corona at this potential?
Any help with this would be greatly appreciated as I cannot seem to be able to find this type of information on the net, I can find it for sphere's, but not for toroids.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Try looking in:
J. A. Hernandes and A. K. T. Assis Electric potential for a resistive toroidal conductor carrying a steady azimuthal currentPHYSICAL REVIEW E 68, 046611 ~2003!
J. A. Hernandes and A. K. T. Assis Surface Charges and External Electric Field in a Toroid Carrying a Steady CurrentBrazilian Journal of Physics, vol. 34, no. 4B, December, 2004
Which can both be downloaded for free in English and as .pdf - together with other similar papers on toroids and spheres - from Dr Assis' publications web page here:
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
This document has the exact formula for the breakdown voltage of a toroid. It is a complicated series: This program can do the calculations, and many others:
A toroid uses less material than an oblate spheroid, and is not much more complicated to make.
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Toroid's vs Sphere as HVDC Terminal
