208 Single Phase vs. 208 3 Phase
When building your datacenter you may want to consider pulling 3 phase power to the rack level. 3 phase power is delivered more efficiently, increases total rack power and could save quite a bit of money in the long run. We have outlined the Pros and Cons of going to 3 phase below, but first, let’s briefly talk about how 3 phase power is delivered.
3 phase power is the most efficient way to produce and distribute electricity. Nearly all power in the world today is generated as 3 phase. 3 phase power combines three electric circuits into one and is supplied over three wires which are typically labeled X, Y and Z in the United States. The line voltages between the three possible pairs of wires are XY, YZ and XZ. For industrial applications 3 phase power is more constant over time making it better suited than single phase power for applications like large industrial loads. This is due to the fact that when a single phase is crossing through zero the two remaining phases are non-zero, either positive or negative, ensuring that the load has a more constant source of power.
Please take a look at the graph below, it illustrates the differences in power types.
| Power Drop | Power in kW (derated 80%) | # of Branch Circuits | # of Poles | Branch Circuit Protection | 120 V Support | 208 V Support |
| 208 V 20 A | 3.33 | 1 | 2 | N | N | Y |
| 208 V 30 A | 4.99 | 2 | 2 | Y | N | Y |
| 208 V 3 Phase 30 A | 8.64 | 3 | 3 | Y | Y (Wye) | Y |
| 208 V 3 Phase 60 A | 17.28 | 6 | 3 | Y | Y (Wye) | Y |
3 Phase Pros
- Power is delivered more efficiently, for example may not need transformers meaning no step-down loss
- Greater power at the rack level
- Lower maintenance costs
- Lower number of whips required at the rack
- Less poles taken up at the distribution panel
- Less rework required as datacenter grows
3 Phase Cons
- High upfront costs if doing conversion from single phase
- Loads must be balanced
- High voltage can be dangerous if not handled properly
