kW, kVA, and power factor
- BY BISON
Table of Contents
This blog post will discuss kW, kVA and power factor. BISON also discuss how to calculate power factor using kW and kVA.
Let’s get started.
kW: actual power
kW is the amount of power converted to useful output. Therefore, kW is called real power or working power.
kVA: Apparent power
kVA is simply a measure of apparent power: it tells the total power used in the system. In a 100% efficient system, kW = kVA. However, electrical systems are never 100% efficient, so not all systems’ apparent power is used for practical work output.
What is the power factor, and why is it important?
Power factor is a performance of energy efficiency. It’s usually expressed as a percentage — the lower the percentage, the less efficient the power usage.
Power factor (PF) is the ratio of operating power (measured in kilowatts (kW)) to apparent power (measured in kilovolt-amperes (kVA)). Apparent power, also known as demand, measures the power used to run machinery and equipment over a certain period. It is obtained by multiplying by (kVA = V x A). Results are expressed in kVA units.
PF represents the ratio of the real power used in the circuit to the apparent power delivered to the circuit. A power factor of 96% means a higher efficiency than a power factor of 75%. In many regions, a PF below 95% is considered inefficient.
How to understand the power factor
Beer is active power (kW) – Useful power or liquid beer is energy that does work. This is the part you want.
FOAM is reactive power (kVAR) – FOAM is wasted or lost power. The energy generated does not do any work, such as heat or vibration.
MUG is apparent wattage (kVA) – MUG is the power demanded or the power provided by the utility.
If the circuit is 100% efficient, demand will equal available power. When demand exceeds available power, utility systems are stressed. Many utilities add demand charges to large customers’ bills to offset the difference between supply and demand. For most common utilities, demand is calculated based on the average load placed over a 15 to 30-minute period. If the demand is irregular, the utility must have more spare capacity available than if the load demand remains constant.
Peak demand is when demand is highest. The challenge for utilities is to provide electricity to handle each customer’s peak. Using electricity when the highest demand disrupts overall supply unless sufficient reserves exist. As a result, utilities pay for peak demand. The utility may even take the largest peak and apply it for the entire billing cycle for some larger customers.
Utilities charge surcharges to companies with lower power factors. The cost of losing efficiency can be high — akin to driving a gas-guzzling car. The lesser the power factor, the less efficient the circuit and the more the overall operating cost. The higher the operational costs, the more likely the utility will penalize customers for excessive usage. In most AC circuits, the power factor will never equal one because there will always be some impedance (interference) on the power line.
How to calculate the power factor
To calculate the power factor, you need a power analyzer or power quality analyzer that measures both operating power (kW) and apparent power (kVA) and calculates the kW/kVA ratio.
The power factor formula can be written in other ways:
PF = (True Power)/(Apparent Power)
or
PF = W/VA
Watts measures useful power, while VA measures delivered power. The ratio between the two is essentially the ratio of useful power to supplied power.
A poor power factor means you are using electricity inefficiently. This is important for companies because it can lead to the following:
Thermal damage to insulation and other circuit components
Reduce the helpful power available
Requires increased conductor and device size
Finally, the power factor increases the overall cost of the power distribution system because a lower power factor requires a higher current to power the load.
The kVA to kW calculations
These two units of power are essential for solving many problems in physics. The formula for converting kVA to kW is:
kVA= kW/PF
As an example: if the power factor is 0.2 and kW is 160, then kVA = 160/0.2 = 800 kVA.
kW to kVA calculations
The calculation of kVA in science is critical.
To convert kW to kVA, use the following formula:
kW=kVA×PF
As an example: If the power factor is 0.2 and kVA is 200, then kW will be:
kW=200kVA×0.2 = 40kW
Difference between kW and kVA
The power factor is the main difference between kW (kilowatts) and kVA (kilovolt-amps). kW is the unit of active power, and kVA is the unit of apparent power. Therefore, the defined and known power factor is an approximation (usually 0.8), and in kW to kVA calculations, the kVA value will always be greater than the kW value.
Among industrial and commercial portable generators, kW is most commonly used in US generators. Most of the world mainly uses kVA as a generator set.
To explain in more detail, the kW rating is primarily a result of the power output that the generator can deliver based on the engine’s horsepower. kW is calculated using 0.746 times the horsepower rating of the engine.
For example, if you have a 600-horsepower engine, it is rated at 473 kilowatts.
Kilovolt-ampere (kVA) is the generator capacity end. Gensets are usually shown in two ratings. To determine the calculated ratio of kW to kVA, the following kW to kVA formula is used. 0.8 (pf) x 750 (kVA) = 600 kW
Things to remember
- Both kVA and kW are units of measurement for power.
- kVA or kilovolt-ampere refers to only 1000 VA. It refers to the apparent power available to the system.
- kW or kilowatt refers to the power that is converted into usable power.
- The power factor is simply the ratio of the active power absorbed in a circuit to the apparent power flowing in it. It shows the efficiency of the system.
- The power factor is from 0 to 1, with 1 representing the most efficient system.
- The kW to kVA conversion formula is kW= kVA x Power Factor (PF)
- In the case of DC, there is no difference between kW and kVA, whereas in the case of AC, kVA, and kW vary according to power factor.
- The value of kVA is always greater than kW.
Conclusion
So in this blog post, we’ve seen kW, kVA and power factor in detail. We’ve also discussed how to calculate power factor using kW and kVA.
What’s the relationship between KVA and KW for AC and DC circuits?
The relationship between KVA and KW for AC and DC circuits is as follows:
For a DC circuit:
Power factor = 1
kilowatt = kilovolt-ampere
For AC circuits:
Power factor >1
kW=kilovolt-ampere*PF
How many kilowatts is a kilovolt-ampere?
kW or kilowatt is a unit of electrical power. It’s equal to 1,000 joules per second and measures the rate at which energy is transferred. This means that in a DC circuit, one kVA equals 1 kW. This means one kVA equals 1,000 watts.
How does the power factor affect kVA?
At unity power factor (100%), a generation and distribution network capacity of 2,000 KVA is required to deliver 2,000 KW. However, if the power factor drops to 85%, a capacity of 2,353 KVA is needed. So we see that a lower power factor hurts generation and distribution capacity.
What is a good power factor?
The ideal or good power factor is unity or one. Less than one means that additional power is required to complete the actual task at hand. All electrical current causes losses in the distribution and supply system. A load with a power factor of 1.0 produces the most efficient power load.
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