i have a 10 kva 110v transforma to calalate current do i use supply or load voltage at full draw?

Question

need to know what current a transforma will draw

i uderstand ohm law but what i'm after is if a transforma has no input details ie current ect and i what to know what rated mcb to use to protect it do i calculate with input or out put voltage

Answer 1

Some drivel here ;-)… To answer your question, you use the rating, i.e. 10kVA (note power out is ~ = to power in, there is very little power loss) and the supply voltage. US = 10kVA/110v = 90A. UK 10kVA/240 = 41A.

Answer 2

10kVA transformer with 110V output.

-Protection on the primary
single phase current input is I=P/V ie if V=230V then I=43.5A
three phase current input is I=P/3V ie if V=230 then I=14.5A
the difficult part with 3 phase is to understand the difference between line and phase voltages the above calculation uses phase voltage. You can do a lot of confusing maths and proofs which may/or may not help you get it into you head. simplest way is to assume a star/star transformer and calculate currents/voltages as if single phase and multiply by three when necessary. It is good practice to protect on the primary and secondary. To protect on the secondary do the same calculation. The transformer will consume negligible load.

Answer 3

A transformer "draws" zero current. The current is drawn by the load attached "downstream" of the transformer.

All transformers have dual voltage and dual current ratings. (Sometimes three, depending on how the output side is achieved).

The kVA rating of the transformer is fixed; this represents the power rating.

It also has a "supply side" rating: supply voltage and supply current (where V * A = kVA, accouting for possible wye or delta connections). And it has a (sometimes different) "demand side" rating: demand voltage and demand current (again, V * A = kVA, adjusting for wye-delta connections).

If, in your case, 110 V is a three-phase voltage on the supply side and the incoming connection is WYE, the supply side current will be:

(kVA) / (sqrt(3) * (volt/1000)) = 10 / (1.73 * 0.11) = 52.49 amps

Answer 4

10 Kva Transformer

Answer 5

The current will be different in the primary and the secondary. If you want to calculate the primary current at full load, divide 10000 by the primary voltage. e.g. if the primary voltage is 480V then the primary current will be 10000/480v or 20.8 amps. The secondary current at full load will be 10000/110v or 90.0 amps.

Answer 6

Its the output of the transformer. That is how you design an application. You look at what you will be powering and use a transformer that will handle that specific load.

Answer 7

10kva Transformer