TRANSFORMER COMPONENTS

• Tank

The transformer tank or enclosure of a power transformer is fabricated of welded

steel. The tank contains the transformer core and coil assembly. It is normally filled

with mineral oil or a synthetic nonflammable insulating liquid that is used as an

insulating and cooling medium.

• Bushings

The electrical power circuits must be insulated where they enter the tank. A bushing

provides an insulated oil-tight and weather-tight entrance for the conductor into the

transformer. It is usually composed of an outer porcelain body, and at higher

voltages, additional insulation in the form of oil and wound paper is used within the

porcelain column.

• Conservator

On larger transformers (over 500 KVA), a reservoir of oil is maintained in a tank at a

level above the cover of the transformer which is connected to the transformer by a

pipe. This is known as a conservator tank (expansion tank) and keeps the main tank

completely full of oil at all times, permitting expansion and contraction. An oil level

indicator with an alarm circuit is provided to indicate the oil level in the conservator

tank.

• Breather

The conservator tank has a breather to the outside. In order to take care of the

expansion and contraction of the cooling liquid with varying temperatures, smaller

units have an air space above the oil, which is connected to atmosphere by a breather.

This breather is, arranged to prevent the entry of moisture, snow, etc, into the

transformer

• Radiators

Radiators are fitted to the tank so that a larger surface is reached by the liquid

flowing into the top, down the tubes of the radiators and back into the bottom of

the transformer.

• Cooling fans

Fans blow air across the radiators to increase the cooling of the oil.

• Off Load Tapchanger (OLTC)

To change the turns ratio on the source winding, a switch is operated by a handwheel

on the exterior of the tank. The handwheel is used to operate a switch within the

tank via an exterior operating rod and interior insulated operating rods. The switch

takes the form of fixed terminals or contacts arranged in a circle. Turning the

handwheel moves the contact or finger around the centre of the circle to complete