[Physics Class Notes] on Difference between KVA and KW Pdf for Exam

One of the primary differences between kW (known as kilowatt) and kVA (known as kilovolt-ampere) is the power factor. The unit of KVa is used to represent apparent power and KW is used to represent the real power of an electrical system. Both of their usages differ in electrical circuits because of the difference between AC and DC circuits. When we consider a DC circuit, the kW and kVA are equal because the current does not get out of a phase. But, when we consider an AC circuit, we could find out several differences.

Generally, the kW rating is the power which is the resulting output a generator can supply which is based on the horsepower of an engine.  The kW is figured out by horsepower rating of the times of the engine.  If kW is the amount of force we can work with, kVA explains the amount that is being used in the framework. Eg: When we say that if we have a 500 horsepower engine it has a kW rating of something around 373. The kilovolt-amperes which are denoted by kVA are the generator end capacity. In this topic, we have learned the difference between kilowatt and kVA. Let us dive more into it.

Difference Between kVA & kW

Kilowatt, which is denoted by kW, is the unit that we have learned in school and how electricity at home is rated and the unit can be seen in our electricity bill. 

So, the question arises what’s the difference between kVA & kW? How do we convert both of them?

kVA is said to be a measure of apparent power. It tells us the total amount of power that is used in a system. In a 100% efficient system kW = kVA. However, the electrical systems are never 100% efficient, and therefore, not all of the power of the system which is apparent is being used for useful work output. 

The kW that we are aware of is the amount of power that is converted into a useful output. The kW is said to be therefore called actual power or working power. We can easily convert between kVA and kW if we know the efficiency of the electrical system. The efficiency in the Electrical system is expressed as a power factor between 0 and 1.

The kW is the amount of ‘actual power’ an electrical system has. This will show how much power is being converted into useful work that is basically for working output.

To convert kW to kVA we first need to know the efficiency or power factor of the system. The factor which is of Power is denoted by pf and is measured on a scale from 0 to 1.

The kW to kVA conversion formula is –

kW = kVA × PF

Where kW is the unit estimating real power,

kVA is the unit estimating apparent power,

PF is the Power Factor.

In the kW to kVA conversion formula kW is directly proportional to kVA, which implies that-

When kW increases, kVA will increase.

When kW decreases, kVA will decrease.

When kVA decreases, kW will decrease.

When kVA increases, kW will increase.

On average we can easily say that a generator has a power factor of 0.8.

The formula used for converting kW to kVA is: kW / pf = kVA e.g. 200 kW / 0.8 pf = 250 kVA

The formula which is for converting kVA to kW is: kVA x pf = kW e.g. 250 kVA x 0.8 pf = 200 kW

These calculations can help us in various industries. Eg: If we want to purchase generators from our local sales, the engineer will be able to help us identify the most suitable equipment for our project. They will take the time to get to know about our job and discuss exactly what we will be powering and for how long. From there they can advise on the generator which is most suitable for us.

kVA to kW Conversion

These two units of power are significant to solve many problems in physics. kVA to kW formula conversion is: kVA = kW / PF

Difference Between kW & kVA Conversion

To convert kW to kVA the formula used is:

kW=kVA × PF

Did You Know?

• A very small fraction of kVA is accessible to do any work, the rest fraction is considered in the current.

• kW represents the actual power that does the valid work.

• In the DC circuit, the kW and kVA are both equal because the current does not go out of the phase. While in the  AC circuits, many differences can be found.