Transformer Rating in KVA

The power rating of a transformer generally expressed in KVA (Kilo Volt Ampere). KVA or apparent power is the product of Voltage and Current (Ampere). Generally a transformer involved in step up or step down of voltage where power is remaining same. Its mean, input power and output power of a transformer is equal; changes happen in voltage and current. In a step down transformer, voltage is decreasing at output and current is going higher then input.

There are two type of losses in transformer; Copper Losses and Core Losses (Iron Losses).   

When electrical currents pass through a conductor or winding, it produced heat. This transfer of energy is known as Copper losses.

The expression of Copper losses is: Copper Loss ∞ (I².R)

Here, I = Electrical Current

R = Resistance of Conductor or Winding.

Core Losses depends on voltage. By altering magnetic field in a core of a transformer, some power is transferred and lost through the core dissipated as heat and noise.

So, Copper losses depend on current and Core losses depend on voltage. Power factor is the term which is coming when a load is connected. Power factor is considering by the type of load; Inductive, capacitive or pure resistive. Manufacturers don’t know the actual power factor when they develop a transformer. Power factor depends on the types of load. With all of these reasons, transformer power rating is rated as KVA.