# Transformer rating in KVA not in KW

Transformers are rated in kVA (kilo-volt-amperes) rather than kW (kilo-watts) for several reasons:

1. Power Factor Variation: Transformers are often used to change voltage levels in electrical systems. The power factor of a load connected to the transformer can vary widely. Power factor is a measure of how effectively electrical power is being converted into useful work. In many cases, the power factor is less than 1, which means that not all of the apparent power (kVA) is converted into real power (kW). By using kVA ratings, transformers account for this variation in power factor.
2. Reactive Power: Transformers can also supply or consume reactive power, which is required for the establishment of magnetic fields in the transformer core. Reactive power doesn’t perform useful work, but it’s necessary for the operation of the transformer. The kVA rating takes into account both real power (kW) and reactive power (kVAR).
3. Universal Rating: kVA is a universal rating system that can be used for all types of loads and applications, whether it’s resistive, inductive, or capacitive. kW, on the other hand, is specific to resistive loads and doesn’t account for reactive components.
4. Simplified Design: Using kVA simplifies the design and specification of transformers because it considers the total apparent power, which is the vector sum of real power (kW) and reactive power (kVAR). This simplifies the engineering calculations involved in transformer design.

In summary, transformers are rated in kVA to account for power factor variations, accommodate reactive power requirements, provide a universal rating system, and simplify design considerations. While kW is useful for quantifying the actual work being done, kVA provides a more comprehensive rating that considers the complex nature of electrical loads.

### What is difference between KVA and KW

kVA (kilo-volt-amperes) and kW (kilo-watts) are both units of electrical power, but they represent different aspects of electrical power in an AC (alternating current) circuit:

1. kVA (Kilo-Volt-Amperes):
• Apparent Power: kVA represents the apparent power in an electrical circuit. It is a measure of the total power in the circuit, which includes both real power (kW) and reactive power (kVAR).
• Real Power and Reactive Power: In an AC circuit, real power (kW) is the power that performs useful work, such as lighting bulbs or turning motors. Reactive power (kVAR) is the power that is needed to establish and maintain the electromagnetic fields in inductive loads like motors and transformers but doesn’t do any useful work.
• Power Factor: The ratio of real power (kW) to apparent power (kVA) is called the power factor. It is a measure of how effectively electrical power is being converted into useful work. A high power factor (close to 1) indicates efficient power usage, while a low power factor indicates inefficiency.
1. kW (Kilo-Watts):
• Real Power: kW represents the real power in an electrical circuit. It is the portion of power that is actually doing the work, such as generating heat, light, or mechanical motion.
• Directly Useful: kW is a straightforward measure of the actual work being performed by an electrical device or system. It is the power that you are billed for by your utility company because it represents the energy consumed.

In summary, the main difference between kVA and kW is that kVA accounts for both real power (kW) and reactive power (kVAR) and represents the total power in an AC circuit, whereas kW represents only the real power, which is the portion of power that is doing useful work. Power factor is an important concept in understanding the relationship between kVA and kW because it quantifies how efficiently electrical power is being utilized in a system.