Choosing a suitable high-power power frequency online UPS (10kVA and above) requires a comprehensive evaluation from multiple dimensions, including load characteristics, scenario requirements, reliability, scalability, and cost.
1、 Clarify basic requirements: power, load, and environment
1. Calculate the load power and type
Active power (kW):
Measure or calculate the total power of all devices, with 20% to 30% redundancy reserved for future expansion.
Formula: UPS capacity (kVA)=load active power (kW) ÷ power factor (UPS is usually 0.8~1.0).
Example: For an 80kW load (power factor 0.9), a UPS capacity of ≥ 89kVA is required, and a 100kVA model can be selected.
Load type:
Linear loads (servers, instruments): Pay attention to output voltage stability (within ± 1%) and harmonic distortion (THD ≤ 3%).
Nonlinear load (switching power supply): The peak coefficient should be ≥ 3:1 to avoid overload.
Inductive loads (motors, air conditioning): Due to the compatibility of the built-in transformer, more than 30% of the capacity needs to be reserved for power frequency UPS.
2. Determine backup time and redundant architecture
Backup time:
Short latency (5-30 minutes): relying on diesel generators, suitable for stable power grid scenarios (such as data centers).
Long delay (1-8 hours): Medical and industrial scenarios require independent battery systems, battery capacity calculation:
Battery capacity (Ah)=(UPS power x backup time) ÷ (battery voltage x efficiency) (efficiency is taken as 0.9, battery voltage needs to match UPS model).
Redundant architecture:
Single machine mode: Low cost, suitable for non critical loads.
N+1 parallel machine: 1 redundant machine, reliability improvement (such as 10 100kVA parallel machines with a total capacity of 900kVA).
2N Dual Bus: Fully independent dual power supply, used in zero tolerance scenarios such as finance and large data centers.
3. Environmental and power grid conditions
Input range: Select wide input in industrial scenarios (such as 120~300VAC, 45~65Hz) to reduce battery discharge; The optional standard range for stable areas is 220V ± 15%, 50Hz ± 5%.
Environmental adaptability: Choose temperature resistant models (-10 ℃~40 ℃) for high temperature environments, and protective enclosures are required for outdoor installation; Pay attention to the load-bearing capacity of the computer room (large UPS can weigh several tons).
2、 Comparison of core performance indicators
Suggestions for selecting key requirements for indicators
Efficiency at full load ≥ 93%, half load ≥ 92% (affecting long-term electricity costs) Compare efficiency curves at different load rates and select the model that matches the actual load (such as long-term 50% load, prioritize half load high-efficiency models)
Dynamic response voltage fluctuation ≤ ± 5%, recovery time ≤ 20ms. Request manufacturer's test report and pay attention to transient performance from no-load to full load
Overload capacity: 125% load lasts for 10 minutes, 150% lasts for 1 minute. Industrial scenarios require higher overload (such as 200% instantaneous overload)
Harmonic suppression input THDI ≤ 5%, output THDU ≤ 3%. Medical/financial scenarios can choose 12 pulse rectification or filter
Intelligent battery management for charging and discharging, temperature compensation, supporting lithium/lead-acid high-frequency scenarios with priority for lithium batteries (maintenance free), and compatible with multiple battery types for power frequency machines
3、 Reliability and Scalability Design
1. Redundancy of key components
Modular design: The power module and battery module support hot swapping (such as APC Symmetra PX) and can be replaced online in case of failure.
2. Scalability
Parallel capability: Supports 4-8 units in parallel (such as Eaton 93E series), with a maximum capacity of several MVA, meeting future expansion needs.
Communication interface: Standard SNMP, RS485, optional Modbus and other protocols, connected to dynamic environmental monitoring systems (such as Huawei iManager).
4、 Cost and Lifecycle Management
1. Initial cost vs long-term cost
Equipment procurement: The initial cost of power frequency machines is higher than that of high-frequency machines, but they have a longer lifespan (10-15 years) and stronger impact resistance.
Operation and maintenance costs:
The maintenance cycle of power frequency machine transformers is long (5-8 years), but they are heavy (100kVA about 800kg) and have high installation costs.
Battery replacement cost: Lead acid batteries take 3-5 years to replace, and lithium batteries take 8-10 years to replace, which need to be included in TCO (Total Cost of Ownership).
Summary: Four step selection method
Capacity calculation: Determine UPS capacity by reserving redundancy based on load power and type.
Fixed architecture: single machine, N+1 parallel or dual bus, matching reliability requirements.
Check indicators: core parameters such as efficiency, overload, harmonics, etc. benchmark against scene requirements.
Look at extensions: parallel capability, communication interface, battery compatibility.
By following the above steps, it is possible to avoid "capacity shortage" or "resource waste" and ensure the stability and efficiency of the UPS system throughout its entire lifecycle. If customized solutions are needed, information such as load list and data center environment can be provided for further optimization.
