The basic starting point is the element-wound with a number of layers of biaxially oriented polypropylene film between layers of conductor aluminium foil. The foil edges extend on opposite sides. Heavy duty leads are attached to the extended edges of aluminium foil.The units are suitably insulated, enclosed in a container and impregnated after thorough drying and degassing to high vacuums.

The impregnant is a low-loss non-PCB capacitor oil. This gives overall losses of less than 0.2 watt/KVAR. There are water cooled cooling coils, which carry away the internal heat and keep the hot spots and overall unit temperatures low. There are no internal fuses. These units do not have internal discharge resistors excepting those rated at 180 Hz.

The units are degreased and painted with a coat of phosphetiser, primer and two coats of synthetic enamel paint. They are tested against leakages before painting.

The housing for these units must be made from non-magnetic material. Non-magnetic stainless steel is used for 180Hz, otherwise Aluminium container is used.

These units are water-cooled. Water cooling copper pipes are firmly soldered to one conducting size of the capacitor stacks. They are firmly soldered to the top of the capacitor body, in case the return terminal of the capacitor is also firmly connected to the body. Otherwise these pipes are brought out through insulators.

The pipe and pipe construction should have no leakages as such they are tested to high pressures.

Units rated at 180Hz are forced to be air cooled instead of water cooled.

Because of high frequencies and generally low voltages, the rated capacitor currents are normally high compared to capacitor currents of similar capacitors at rated mains frequency. The current carrying portions inside the capacitor units are adequately designed.