UPS systems are primarily rated using three standard units: Kilowatts (kW), Volts Amps (VA), or Kilo-Volt-Amperes (kVA).
Understanding the power rating of a UPS (Uninterruptible Power Supply) is crucial for selecting the right unit to protect your equipment. These ratings indicate the capacity of the UPS system.
Understanding UPS Rating Units
According to standard practices, UPS systems are typically rated in either kilowatts (kW), volts amps (VA), or kilo-volt-amperes (kVA). These units represent different aspects of the power handling capability of the UPS.
VA and kVA Ratings
The VA (Volts Amps) or kVA (Kilo-Volt-Amperes) power rating essentially represents the power limitation accepted by the UPS. This rating signifies the apparent power capacity of the unit. It is the product of the voltage and the current the UPS can handle.
- VA: Used for smaller UPS units.
- kVA: Used for larger UPS units (1 kVA = 1000 VA).
kW Rating
The Watts rating (kW) represents the power output of the UPS and determines the unit's 'real power'. This is the actual power consumed by the connected equipment and what the UPS can continuously supply. Kilowatts account for the power factor of the connected load.
- kW: Kilowatts (1 kW = 1000 Watts). Represents the usable power output.
Comparing VA/kVA and kW Ratings
It's important to note that the VA/kVA rating is usually higher than the kW rating for a given UPS. This difference is due to the power factor, which relates real power (kW) to apparent power (VA).
| Rating Unit | Represents | Definition (based on reference) |
|---|---|---|
| VA | Apparent Power / Capacity | Power limitation accepted by the UPS |
| kVA | Apparent Power / Capacity | Power limitation accepted by the UPS |
| kW | Real Power / Output Power | Power output and determines the 'real power' |
When choosing a UPS, you must ensure that both the total VA requirement and the total kW requirement of your connected equipment are within the UPS's rated capacity. The lower of the two limits (based on the UPS's specific VA and kW ratings) is the effective maximum load the UPS can support.
