To illustrate the use of this table, suppose we need a wire for use at 10 KV AC RMS. 
The sizes above and to the right of the step lines are good for use at this voltage, 
the optimum size being AWG 18 with X 5.0 CR insulation thickness, having nominal 
insulated diameter of 3.7 or 3.8 mm.  If the duty cycle is low, i.e. on-time under High
Voltage is say 10%, then we can work with smaller diameter wires also.  Please refer
to Questionnaire under Free Design Service page of this site.