It's crucial to have a clear understanding of the terminology when it comes to choosing the right amount of power. The power capacity of systems is usually expressed in kilowatts (kW) and/or kilo-volt-amperes (kVA). For instance, a 1 kVA UPS means it has the ability to handle 1,000 volt-amperes.
When it comes to AC power, the formula is simple: "watts = volts x amps." So, one may think that a 1,000VA UPS can handle 1,000 watts. However, it's not that straightforward. UPS systems have inefficiencies, and some power is usually lost in the transformers and circuitry of the backup system, also known as reactance. To address this, most UPS manufacturers specify a "power factor" that is used to calculate the maximum wattage the UPS system can handle. Hence, the formula becomes: watts = volts x amps x power factor.
For instance, a 1kVA UPS from N1C has a power capacity of 900 watts for the connected equipment. This implies that the UPS has a power factor of 0.9.
Operating a 1 kVA UPS at 900 watts, or 100% of its capacity, is not recommended as it can cause the UPS to fail due to a short circuit. This would render the purpose of having a UPS, which is to provide backup power during outages and short circuits, useless. It is better to utilise a lower wattage, such as 450 watts, which would result in the UPS running at 50% of its power. This will not only prolong the battery runtime during power outages but also increase the lifespan of the UPS by reducing the need for maintenance and repairs.
To determine the maximum load capacity for your UPS system, it's important to check the wattage rating on the label of each device you're connecting to the UPS. Once you've added up their wattage usage, it's important to leave a margin of 20% error. This means that you should only run the UPS system at 80% of your calculated maximum load. This will provide a safety buffer during peak conditions when certain devices may cause a spike in wattage usage, such as during the initial startup of a hair dryer. This will help prevent overloading the UPS and ensure it operates smoothly.
If you require 900 watts for your UPS system, it's recommended to opt for a 2 kVA system to ensure you have enough capacity. Running it at 50% of its load capacity will provide additional room for potential maximum loads, avoiding any early stress on the system. If you choose a 1 kVA system with a 900-watt load, you will be operating at 100% capacity from the start, which can be stressful for the system and may result in early failure.
The next factor to consider is your battery runtime needs.
If you're connecting equipment that is located in a different floor or wing of your office complex, or at an offsite location, you may require a longer battery runtime for your UPS to protect your load and keep your devices running. On the other hand, if you know your building has a generator that will quickly activate during an outage, you may be able to settle for a shorter battery runtime.
As an example, a 1kVA UPS from N1 Critical Technologies provides 11 minutes of runtime at a 100% load (900 watts). If your load was 900 watts and you used a 2kVA UPS from N1 Critical, you would be operating at 50% load, giving you 24 minutes of runtime. If you ran 900 watts on a 3kVA UPS from N1 Critical, you would be operating at 33%, providing you with more than 30 minutes of runtime.
Lithium-ion UPS systems offer a longer battery runtime compared to traditional lead-acid systems. The lithium-ion battery packs utilised in N1 Critical UPS systems store more power in a smaller space, enabling extended runtime in the same size UPS unit.
This gives users the advantage of being able to wait out an outage for a longer period or provide extra travel time during a power outage. These additional minutes can be crucial, making lithium-ion batteries the future of energy storage in UPS applications.
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