The Secure Power knowledge base aims to give you the information you need to navigate the jargon and deliver straightforward advice around the terminology used within uninterruptible power systems.
OUTPUT WATTS, PF AND KVA
Watts, power factor and Kilo Volt Amperes, what are they and how are they linked? In this KB article, we will look at how these three ideas are intertwined and what they mean to you when looking at your power solution.
When you size a UPS these 3 metrics are the single most important aspect to consider is that the UPS you choose is capable of providing sufficient current (Watts) to the connected equipment. UPS in general though are provided with the measurement of kVA, so how do we get to know the watts that this is equal to? Let first break down what each means on their own and then look at how they affect one another.
Kilo Volt Amperes abbreviated the kVA is the measurement of apparent power in an electrical circuit. This is the predominant measurement for potential output capacity provided with a UPS. In a UPS kVA is not equivalent to Watts on most occasions.
PF (Power Factor)
PF is the term used to describe the relationship between the apparent power (kVA) and the actual power (Watts) a UPS can produce. The Power factor is represented as a number equal to or less than 1. This number is used to represent the difference between apparent and actual power. A PF of 1 is possible and results in no losses, this is referred to as a “unity” PF, this is found in high-end UPS.
Once kVA has had a PF applied, the result is the Wattage of a given electrical system. This wattage can be then used to confirm that the available wattage of the given system is sufficient to support the connected equipment total wattage, or kilowatts.
Let’s use some examples to demonstrate how this would work with a real-world example.
- 1000VA (1kVA) x 0.7PF = 700W
As this example shows a 0.9PF reduces the apparent power of 1000VA down to 700W, the affect PF has on the potential output is negative in the vast majority of cases, At best a unity PF of 1 will leave the VA and W equivalent.
- 20000VA (20kVA) x 0.9PF = 18000VA (18kVA)
- 20000VA (20kVA) x 1PF(Unity) = 20000VA (20kVA)
As you can see from the examples above kVA, PF and Watts are relatively straight forward to use to ensure that the wattage of your UPS is capable of providing sufficient power to meet your needs.
Utility power isn’t always what it should be, the input of the UPS is where it is measured.