Original poster: Steve Conner <steve@xxxxxxxxxxxx>
i`ve calculated the toroid voltage (70 cm diameter) - 1.2 MV -
what height should be the secondary to prevent flashovers?
I believe it should be about 1.2 metres since the breakdown strength
of air is 3MV/m and the tracking strength across a surface is roughly
one-third of that- 1MV/m.
But that's just a rule of thumb. In practice I reckon the secondary
can stand more than 1MV/m since the winding acts as a series of grading rings.