Air conditioning capacitors - the role of air conditioning capacitors

This comes from the structure of the capacitor. The simplest capacitor is made up of plates at both ends and an intermediate dielectric (including air). When energized, the plates are energized to form a voltage (potential difference), but the entire capacitor is non-conductive due to the middle insulating material. However, this is the case without exceeding the critical voltage of the capacitor (breakdown voltage). We know that any material is relatively insulated, when the voltage across the material increases to a certain extent, the material can be conductive, we call this voltage breakdown voltage. Capacitance is no exception, the capacitor is breakdown, it is not an insulator. However, in the secondary stage, such a voltage is not seen in the circuit, so they are below the breakdown voltage work, can be seen as an insulator.