Data centre
Three phase UPS systems for critical loads
Three phase UPS systems, uninterruptible power supplies specified by rating, topology, redundancy and runtime, and put to the manufacturers whose range covers them.
- Rating
- kVA and kWat the load's power factor
- Topology
- double conversion online (VFI)IEC 62040-3 classification
- Redundancy
- N, N+1, 2Nset by the design
- Runtime
- minutes at a stated loadbridges to the generator
- Battery
- lithium ion or VRLAwith its room or cabinet
A data centre UPS carries the load through the seconds between a mains failure and the generator. Its runtime is therefore set by the generator's start and transfer, with margin, not by hours of autonomy.
Redundancy is a design decision and the UPS is bought to it. In N+1 the system has one module more than the load needs, so each module carries a share and the rest carry the whole load when one fails. In 2N two complete systems each carry the whole load alone, fed from separate paths.
What gets specified
| Parameter | Typical options | What decides it |
|---|---|---|
| Rating | kVA and kW per system or module | The IT load and its growth |
| Topology | Double conversion online, line interactive | How clean the output must be |
| Redundancy | N, N+1, 2N, 2N+1 | The availability design |
| Runtime | 5 to 15 minutes at full load is common for data centres | Generator start and transfer time |
| Battery | Lithium ion, VRLA | Footprint, weight, cooling and life |
| Construction | Modular hot swap or monolithic | Growth and maintenance practice |
| Voltage | 400 V three phase in and out | The switchboard |
N+1 and 2N
Break times under BS 7671
Where a UPS serves safety services, BS 7671 classes the supply by how long the break may last, from no break through very short (0.15 s) and short (0.5 s) to medium (15 s). The IET's guidance places a mains floating UPS in the no break class and other UPS types in the very short break class.
Hospitals set the tightest case. Section 710 of BS 7671:2018 requires theatre luminaires, endoscopy and life support equipment to change over within 0.5 s to a source that lasts at least three hours. Other listed equipment must transfer within 15 s to a source lasting at least 24 hours. The first is a UPS duty, the second a generator's.
The performance standard
| Standard | What it sets |
|---|---|
| IEC 62040-3 | Uninterruptible power systems: the method of specifying performance and the test requirements, behind the VFI classification |
What we need to quote
- Load in kW and kVA, today and at full build
- Redundancy: N, N+1 or 2N
- Runtime at a stated load
- Battery chemistry, and where the batteries stand
- Modular or monolithic
- Input and output voltage and the switchboard
- Whether it serves safety services, and the break class they need
Building or expanding a facility?
Send the whole equipment schedule as one project, each item with its own requirements.