A good way to represent this whole concept of reactive power as opposed to treu power is to plot it on a graph.( The circle known as the KVA arc used in the 1st and 4th quadrants. If you follow the arc from the X-axis as if the reactive power were increasong ie pos or neg, you will see the real power decrease in proportion to the reactive power while the KVA stays the same.O
using the X and Y axis as the center of the circle, the circumference of the circle will be the limit of the transformer say 25kva, the X axis will always be used as real power and the Y axis will be used to denote the reactive power.
By observation when reactive power is equal to zero that is when the Y component is zero the KVA=KW, and as soon as there is a reactive component present the KVA will change in accordance to the square-root sum of the squares of the real compnent and the reactive component.
As an example if Real Power is 300 watts and the reactive Q is 400 vars the KVA is " the square root of 300(squared) + 400(squared) which would give 500 Volt-Amps and an angle of 53.13 degrees
the angle or power factor is ArcTan (X/R) or in this case reactive power/real power.
Once the power factor is known the whole problem falls apart.
Tom
