When choosing an uninterruptible power supply (UPS) system, several factors need to be considered. In addition to determining the required topology and whether single-phase or three-phase units are needed, correctly calculating the required UPS power is also crucial. Therefore, when choosing a UPS uninterruptible power supply, it is necessary to consider the expected total load (combined voltage and current of all connected devices), capacity (maximum power output of the devices), and backup time required by the UPS battery (the time the UPS power supply can support the devices during a power outage).

Although most major UPS power manufacturers offer useful product selectors and runtime calculators, please continue reading to learn how to determine the size of UPS uninterruptible power load and runtime in an old-fashioned way.

A、 Factors to consider when calculating UPS power load and operating time:

Due to the varying specifications of UPS power products, it is crucial to carefully consider all aspects when selecting the most suitable specifications to meet different needs. The three most important factors to consider are the rated value of the UPS uninterruptible power supply system, the load it will support, and the required operating time.

1. UPS uninterruptible power supply system parameters:

The rated power of UPS uninterruptible power supply systems is usually kilowatts (kW), volt amperes (VA), or kilovolt amperes (kVA). The rated power of VA or kVA represents the power limit accepted by the UPS, while the watt rating is the power output of the UPS, which determines the "actual power" of the equipment.

In a direct current (DC) circuit, watts=volts x amperes (in other words, 1kW=1kVA). However, when an uninterruptible power supply system uses alternating current (AC) - just like most data centers and other buildings - it reduces the available power (watts) in apparent power (volt ampere). The ratio of these two numbers is called power factor. The power factor of an AC power system is defined as the ratio of the actual power absorbed by the load to the apparent power flowing in the circuit, calculated as: watts=volts x amperes x power factor. The power factor varies depending on the UPS. For example, a 100kVA UPS system with a power factor of 0.8 can only support an actual power of 80kW.

2. Power load:

UPS load refers to the total power consumed by connected electrical equipment. To calculate the load, you need to add up the total wattage of each device connected to the UPS. For example, if you want UPS to support 120W PCs, 30WVPN routers, 960W servers, 280W network switches, and 480W storage devices, the total required load is 1870W.

3. Battery capacity:

Although the load represents the total equipment that the UPS power supply will be responsible for protecting, it is also necessary to determine the desired duration for the load to maintain normal operation during power outages. This will establish the operating time of the UPS uninterruptible power supply system. Each UPS uninterruptible power supply system has a battery pack that will provide limited power if there is no mains supply. However, many UPS uninterruptible power supply specifications can be equipped with external battery modules to extend operating time by a few minutes or hours. The battery capacity is measured in AH or Amp hr units.

B、 How to calculate UPS power load and running time:

Many UPS uninterruptible power supply system manufacturers provide online UPS uninterruptible power supply system calculators and selection tools, which can more easily match backup power sources with demand. However, if there is no UPS selection tool, you can calculate the load by collecting measurement values and completing a series of simple steps. It should be noted that although adding more batteries to the UPS power supply can increase battery running time to support the load, it will not increase the capacity of the UPS uninterruptible power supply. So when choosing a UPS uninterruptible power supply system, it is necessary to first ensure the appropriate power of the UPS power supply, and then add batteries to meet the running time requirements.

To determine the power of the UPS:

1. List all equipment and devices protected by UPS.

2. List the amperes and voltages of each device. These parameters can usually be found on the label on the back

3. Multiply amperes by volts to determine volt ampere (VA). Some devices may list their power requirements in watts. To convert watts to VA, divide watts by power factor.

4. Multiply VA by the number of devices to obtain the VA subtotal.

5. Add the VA subtotals together to obtain the total power requirement.

6. Multiply the total by 1.2 to obtain the total. This step considers future expansion.

7. When selecting UPS, please ensure that the VA requirements of the supported devices do not exceed the VA level of UPS.

To determine the backup time, please follow these steps:

1. Multiply the battery rating (in Ah) by the battery rating (in Ah) multiplied by the battery rating (in V) multiplied by the number of batteries multiplied by the battery efficiency.

2. Then divide the number by the load (in watts (W)).

Although runtime may seem like an easy quantifiable thing, understanding the facts behind the numbers can help determine the best backup battery solution for a specific business or application.

C. Please consider the following solutions:

1. UPS runs for 10-15 minutes without the need for a generator - this solution ensures safe shutdown of connected devices and saves on work in progress.

2. UPS and generator with a running time of 10-15 minutes - this solution will keep the connected system running normally until the generator is powered on.

3. UPS with a battery life of two hours or more - in some cases, the generator may not be practical, and organizations wishing to maintain normal operation during prolonged power outages must rely entirely on UPS batteries.