The multiple corona effects

such as space charges

ionized field

radio interference

audible noise and corona losses

etc

can be generated along with the corona discharge. In order to investigate the differences of corona onset voltages generated by different corona effects

a platform using the cylinder corona cage for determining the corona onset voltage was set up. The ion current densities

ionized fields

steady corona current

and ultraviolet photons from smooth conductors with different diameters were measured simultaneously in the experiments. Comparisons of the corona onset voltages from different corona effects are given through the inflexion-point method. Besides

numerical simulations for the corona onset voltage are also presented on the basis of the analytical formulas for ionized field of cylinder structure and the empirical formulas for onset electric field. The calculated results of the corona onset voltages for different conductors can match the measured ones

and the maximum error is less than 2.1%. Therefore

we proposed to use the cylinder corona cage to measure the multiple corona effects and to use the inflexion-point method to determine the corona onset voltage for the smooth conductor.