Because the machines which use power i.e; load, are always rated in KW and the machines which produce power i.e generators, are rated in KVA.
AnswerA motor's mechanical load is expressed in watts (horsepower in North America), so the output power of the motor must also be expressed in watts (horsepower in North America) so that the machine can be matched to its load. You cannot express a mechanical load in terms of volt amperes.
kva*cos(phase angle)
12HP is approximately 10.8 KVA. You would want to use a 15KVA transformer to supply this motor. KW = HP * .75 KVA = KW * 1.2 (These formulas are approximate)
Transformers are rated in VA or kVA. That is because the voltage is limited by the power loss in the magnetic core, and the current is limited by the power loss in the resistance of the windings. The rated voltage times the rated current gives the transformer's rating in kVA.
Rating for DG set and any of electrical machines is calculated in KVA. KVA is calculated as KW/pf. One can calculate the required KVA for DG set with this formulation: (KW/pf)/load rate. For example KW=110, pf=0.8 and one loads the DG at 75%, so KVA= (110/0.8)/0.75=185 KVA.
kva and kw are related as KVA = (KW/PF) pf:power factor
Because it is the current rating of the windings that determine the maxium load current, and the product of rated current and rated voltage, in a.c., is apparent power (in volt amperes), nottrue power (in watts).And, incidentally, the correct symbols are kV.A and kW, not kva and kw.
depending on kva class of the motor between 4-8 times the running current
The same way, as you convert Appels to Carrots ........... There is a formula: KVAr = KVA / KW or cos=KW/KVA > Yes, we are treating KW, KVA, & KVAr as the 3 sides in a 90 deg TRIANGLE ! KW= vertical katede KVAr = horizontal katede KVA = hypotenuse
For a purely resistive load with a unity power factor, 9.41 kVA would equal 9.41 kW. However some equipment such as a motor will have a power factor less than 1. If the power factor is 0.8 then 9.41 kVA would equal 9.41 x 0.8 kW.
Transformer power is given by P=V*I which takes the unit of KVA while that of KW has energy term which is not produced by the transformer.It only steps up or down the voltage.Answer:In a pure D.C. circuit, KW = KVA. However, in any A.C. circuit, there is real power {KW} and apparent power {KVA}, due to the voltage and current being out of phase. Power Factor is the ratio of KW to KVA. Transformers are rated in both KVA and PF. Multiplying the transformer KVA rating times the PF will yield KW.A transformer has separate ratings for maximum voltage and maximum current. Multiply the two together and that is called the VA rating, or kVA for larger transformers. So the transformer rating is independent of the power factor of the load.
One horsepower is equal to 746 watts.
Because its measured in kilo volt amps which is the actual reflection of current flowing through the windings. if kw were used as a rating, then it would have to be stated at some power factor