Re: transformer calculations
Originally posted by wyedelta:Guys: If you compute the current using apparent power (KVA) you also include the transformer loses. What I am trying to say when I wrote the formula was that we must compute the line current for maximum current the transformer can deliver.
I may be misinterpreting your statement. But it seems to me that you are trying to associate ?transformer losses? with ?power factor,? as though the former is the cause of the later. That is not how things work. Power factor is the natural result of wires being wound in circles, and is not a function of the amount of any copper, eddy current, hysteresis, or other losses internal to the transformer.
If power is lost within a transformer (as is the case in all real components), then the voltage at its terminals will be lower, and the current delivered to the world will be lower as well. But for our purposes, we must presume that (losses or no losses), the terminal voltage will be the rated voltage, and the power delivered to the world will be the rated power.
As I said before, your formula is perfectly valid. But to use it, you must first convert the given value of KVA to an equivalent value of kW. That requires you to multiply by an assumed value of power factor (PF). Then, when you use your formula to calculate current, you must first ?solve for current.? That is, you alter the formula to get current on one side of the equation and everything else on the other. In this process, you will divide ?power? (i.e., kW, a value you computed by taking KVA times PF), by that same assumed value of PF. Your final answer will be the same 181 amps.