Acidity
Moisture
Viscosity
Dielectric strength
Soft iron
Rolled steel
Copper alloy
Cold rolled grain oriented
Air releasing
Heat releasing
Pressure releasing
Moisture releasing
Protection from high temperature
Protection from moisture entering in oil
Protection from pressure loading in tank
Protection from both overloading and short circuit
To offer high inductance
To obtain required voltage ratio
To regulate the primary current
To stabilise input and output voltage