Transformer help

Technical Support
1

Hello guys

I have a 3-phase, 250kVa transformer at my site.

Specs on its label are:

250kVa
cooling type: ONAN
freq: 50hz
rated voltage: 20.000/400

My question is:

How many 1phase , 220v , 3500 watt cryptocurrency servers can i run simultaneously without damaging the transformer ?

In on other words, how many amps can each phase withstand , by approaching the limit but without damaging the transformer ?

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3

Theoretically roughly 57 servers total (19 per phase) counting with a power factor of 0.8, but I have no idea if that would damage the transformer or not.

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4 
Transformer rating: 250 kVA
Primary voltage (high voltage side): 20,000 V (20 kV)
Secondary voltage (low voltage side): 400 V
Cooling type: ONAN (oil natural air natural), which is a common cooling system for transformers
Frequency: 50 Hz
Server specs: 220 V, 3500 W per server

Step 1: Calculate the total current capacity of the transformer on the low voltage side (400V):

The power rating of the transformer is 250 kVA, which corresponds to 250,000 VA. The current on the low voltage side (secondary side) can be calculated using the formula:
I=SV
I=VS​

Where:

II = current in amps
SS = apparent power in VA (250,000 VA)
VV = voltage on the secondary side (400 V)

I=250,000400=625 amps
I=400250,000​=625amps

So, the transformer can deliver 625 amps on the secondary side at 400V.
Step 2: Calculate the number of servers you can run per phase:

Each cryptocurrency server consumes 3500 W, and you want to know how many servers can be run per phase. Since you’re operating in a 3-phase system, we’ll distribute the load equally among the three phases.

The formula for the current draw on each phase is:
Iphase=PVphase×3×PF
Iphase​=Vphase​×3
​×PFP​

Where:

PP = Power in watts (3500 W per server)
VphaseVphase​ = Voltage per phase (220 V)
PFPF = Power factor (usually 1 for resistive loads like servers)

For 3500 W of load:
Iphase=3500220×3×1=3500381.8≈9.17 amps per server
Iphase​=220×3
​×13500​=381.83500​≈9.17amps per server
Step 3: Calculate how many servers each phase can handle:

Each phase can handle up to 6253=208.33 amps3625​=208.33amps.

Now, we can calculate how many servers can fit in each phase:
Number of servers per phase=208.339.17≈22.7 servers
Number of servers per phase=9.17208.33​≈22.7servers

So, each phase can handle 22 servers (since we can’t run a fraction of a server).
Step 4: Total number of servers:

Since there are 3 phases, the total number of servers you can run is:
Total number of servers=22 servers/phase×3 phases=66 servers
Total number of servers=22servers/phase×3phases=66servers

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