Why Transfarmer is rated in KVA

Rating of the transformer in kVA

The rating is the load capacity of the machine. It shows the maximum value of the voltage at which the machine is designed and the power consumption occurs at that voltage. The machines are always rated in watts. However, the alternator and transformer are the only machines rated in volts (VA).

Why is the transformer designed in KVA?

The machines that consume electricity are given in KW. However, the main task of the transformer is to transmit the power, not to consume it, i. H. It is designed in VA and not in KW.

There are two reasons that the power of the transformer is in kVA. Let that be understood in detail.

Reason 1: Before starting the topic, you must first understand what the difference between KVA and KW is.

The KVA is the product of KV and Ampere,

KW is the product of KV, ampere and power factor,

The equations above show that power factor are the only terms that make the difference between the two.

What is the power factor?

The power factor only shows the total power consumed by the load. The machines that are designed in KW are designed for the fixed load type. Like the inductive load, the induction machines are always connected.

But here in the case of the transformer, the load is completely unpredictable, and the designer designed the transformer with the unity power factor in mind. The power of the transformer is in KVA and not in KW. The power of the transformer is also given in VA, KVA and MVA, depending on the size of the transformer.

Reason 2: The transformer consumes the power losses. Copper and iron are the two types of losses that occur in the transformer. The copper loss depends on the current (amps) flowing through the windings of the transformer, while the iron loss depends on the voltage (volts). the power of the transformer is in kVA.

How does the power of the transformer depend on its losses?

The power of the transformer depends on the temperature of the windings and oil, which are within the specified limits. But how the temperature in the machine rises. It rises because of the losses. The losses that occur in the transformer increase its temperature. So we can say that the power of the transformer is in KVA.