EI and C cores create high parasitic capacitance everywhere which :

• Worsens the electric field environnement in coil,
• Increases leakage current between layers and wires,
• Creates partial discharge and corona effect,
• Requires more insulation everywhere, increasing cost and reducing cooling efficiency.
• All of them are aging factors that can damage components of an insulated system and IGBT.

With toroidal shape, only the first and last turn area needs more insulation.

With toroidal core, only a few turns of coil with higher voltage stress need the use of reinforced insulation. Reliability is improved thanks to less aging factors due to lower parasitic capacitance.

It can further be improved, using our VPI system (Vacuum Pressure Impregnation).