UPS selection and backup time calculation: Monitor how long it will last after a power outage
Determine which equipment you want to protect first
Monitoring scenarios usually do not require full power supply to the cameras (there is a PoE switch at the front end, But the switches themselves tend to be scattered across floors). UPS focuses on ensuring: Storage/servers, core switches, management platforms in the computer room, as well as key points such as entrances and exits, and perimeters.
How to calculate capacity
Formula: UPS capacity (VA) = Total equipment power (W) ÷ Power factor ÷ Load rate. Generally, the power factor is 0.8~0.9, and the load rate is recommended to be controlled at 60%~80% (leaving a margin and high efficiency).
Example: The total power of the equipment is 800 W, the power factor is 0.9, and the load factor is 0.7. Then 800 ÷ 0.9 ÷ 0.7 ≈ 1270 VA, choose 1500 VA or 2000 VA model.
Backup time
| Requirements | Recommended backup time | Explanation |
|---|---|---|
| Only ensure safe shutdown | 10 to 15 minutes | enough for the server to complete the shutdown process |
| Short-term mains power fluctuations | 30 minutes | Covering most transient faults |
| Continuous operation of key services | 1 to 2 hours | An external battery pack is required |
| Waiting for the generator to start | According to the generator start time + 20% | Need to cooperate with the generator |
Online and backup mode
Backup type The switching time is about 4 to 10 ms, the price is low, and it is suitable for ordinary office equipment. Online (double conversion) The output is always powered by the inverter, and the switching time is zero. The output waveform is pure, making it the right choice for monitoring computer rooms - storage devices are sensitive to power supply quality. Backup square wave output may cause hard disk abnormalities.
Battery life and testing
- The life of lead-acid batteries is usually 3 to 5 years, and the life is halved every time the ambient temperature rises by 8 to 10°C.
- Conduct a load-discharge test every quarter (put it at about 50%) and record the actual backup time.
- Integrate UPS alarm signals into dynamic environment monitoring. Battery low voltage, bypass power supply and other statuses must be able to notify people immediately.