At very high voltages, the physical geometry of the surface at high voltages becomes the key factor to suppress corona generation. Corona occurs when there is an excessive local electric field gradient on an object. Corona is a luminous, audible discharge that produces ionization and may cause electrical breakdown of air near the point. Effective corona suppression is a key factor to be considered when designing high voltage power supply. The role of the corona ring is to distribute the electric field gradient so that the maximum electric field gradient is below the corona threshold, either to prevent the corona discharge altogether, or to transfer the destructive effect of the corona discharge from valuable hardware to the consumable ring. The large diameter smooth sphericity of the corona ring/toroidal coil/sphere helps to control the local electric field, thus inhibiting the generation of the corona. The diameter of the required corona ring/toroidal coil/sphere must also be increased for effective corona suppression to be achieved.

The corona ring works by modifying the shape of the electric field intensity to reduce the worst-case rate of electric field change on the insulator, thereby reducing the peak potential in the surrounding air to about 10 kV per inch of the breakdown voltage (dry air).