Transformer help

[Oz111]

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 ?*

[1714327116]

1714327116

[1714327116]

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[NotFuzzyWarm]

Um.. 250,000*80% load gives 200kw/3500w=57 miners total. The 80% loading is standard safety margin for pulling power 24x7

[Oz111]

Um.. 250,000*80% load gives 200kw/3500w=57 miners total. The 80% loading is standard safety margin for pulling power 24x7

I forgot to specify that it is s19 servers. Does it make any difference?

[NotFuzzyWarm]

No. It does not matter what the load is. Could be a single massive arc light, a data center full of servers or in this case, miners - all that matters is the rated power they pull.

[philipma1957]

That is assuming

A) Just the s19's
B) no fans or other cooling on the Transformer
C) that it is always provided with correct voltage by the power company.

our 320 K-watt trans former has a 5-10% drop in the summer


So you may be 50 in the summer and 55 in the cooler months

Fuzzy knows far more than I do. So you can do the 57 also the gear has a low power option. So if you have proper monitor you can down clock it to low power if it is hot.

[Uhwuchukwu53]

Um.. 250,000*80% load gives 200kw/3500w=57 miners total. The 80% loading is standard safety margin for pulling power 24x7

I see this analysis more accurate they prescription if 19's though I stand to be corrected as need more improvement on calculating how to utilize transformers of such voltage.

[mikeywith]

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

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 ?*

It should be stated on the transformer itself, but the formula is

I= (KVA*1000 ) / (V * square root of 3)

I = 250*1000/400 * 1.732 = 360.8A but that is for 400V, which isn't all that important to your case, so you need to figure out the 230-240V (should also be on the transformer plate) but you can use the same formula without the square root of 3

I = 250*1000/240 = 1041A

But you won't be able to pull 1041 of a single phase, each phase would be maxed out by 1041/3 = 347A or 83KW

83/3.5 = 23 miner on each phase or a total of 69 miners, but that would be pushing the transformer at 100%,  stick to NotFuzzyWarm's adive of at least 20% off, and that would give you 55.2 miners total, but you can't do that so 18 miners on each phase with a total of 54 miners (I rounded the numbers which is why I got you 3 miners less lol).

Obviously, you need to account for cooling, and safely put 10% of the load for that, so cut another 10% from the 54 miners and you get 48 miners only.

[philipma1957]

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

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 ?*

It should be stated on the transformer itself, but the formula is

I= (KVA*1000 ) / (V * square root of 3)

I = 250*1000/400 * 1.732 = 360.8A but that is for 400V, which isn't all that important to your case, so you need to figure out the 230-240V (should also be on the transformer plate) but you can use the same formula without the square root of 3

I = 250*1000/240 = 1041A

But you won't be able to pull 1041 of a single phase, each phase would be maxed out by 1041/3 = 347A or 83KW

83/3.5 = 23 miner on each phase or a total of 69 miners, but that would be pushing the transformer at 100%,  stick to NotFuzzyWarm's adive of at least 20% off, and that would give you 55.2 miners total, but you can't do that so 18 miners on each phase with a total of 54 miners (I rounded the numbers which is why I got you 3 miners less lol).

Obviously, you need to account for cooling, and safely put 10% of the load for that, so cut another 10% from the 54 miners and you get 48 miners only.

. 45-51 is the range of what it can do.

a lot depends the volts going into and out of it.


it if it is supposed to be 400 volts and the power company feeds it 380 volts due to hot weather etc. and it may do more with 420 volts feeding it.

Mikey's 48 number is a good estimate.

[mikeywith]

it if it is supposed to be 400 volts and the power company feeds it 380 volts due to hot weather etc. and it may do more with 420 volts feeding it.

They are going to feed it with 20KV, and then there is a tap changer on the transformer which the electric company will play with to maintain the desired output according to the country code -- since it's impossible to get 20KV across the whole 20KV line, transformer taps can be changed.

So given that his transformer states 20KV high-side and 400V low-side, it simply means if you feed it 20KV it would output 400V if the tap changer is set at default which is usually no.3, now say you are the first transformer on the line, you will get more than 20KV (it needs to be so that the last person can still get 20KV or close), so if yours gets 21KV the electric company would reduce the tap to say no.2 (not randomly -- it's all on the transformed plate), on the other hand, if you are somewhere at the end of the line and getting only 19KV, they would increase the tap to maybe 4, or 5.

The standard where my farm is is 220V, the guys who installed the transformer insisted that I need to keep it at 2 so that my low side voltage is 220V, but I insisted on wanting 230-240, so after back and forth with them they set put it at 3 at my own risk and call them if i changed my mind -- now my low side voltage is at 239v without load, and 235-236v on up to 1MW load, I like these numbers so I never called them back to come change it.

BTW, I wonder what country that is that has 20KV lines, here we don't have that, it's 66kv > 33kv > 11kv is the last HV that feeds the consumer transformer.

[stompix]

BTW, I wonder what country that is that has 20KV lines, here we don't have that, it's 66kv > 33kv > 11kv is the last HV that feeds the consumer transformer.

At least Western and Central Europe, 6KV,10KV, 11LV,15KV, 30-33-35-36...we have it all!  
I think the US still uses 20KV in some states! Europe was pretty divided and everyone was implementing its own grid a century ago, then the whole mumbo jumbo with the territorial changes and now it's way to complicated to bring eveything to a standard anymore.