The power factor data shown below:
fits a curve of the form:
pf = a - b · ec·log(1-x/100)
The efficiency data shown below:
can be transformed to a straight line graph by plotting percentage load over efficiency against percentage load, a follows
It can be seen from the above graph that the value of the function at no load is missing; but can be calculated from
x/η = √3·V·INL·cosφ
Because this curve is a straight line it can be parametised by a simple linear regression routine.
So we now have functions for power factor and efficiency in terms of percentage motor load and we can use these in
P = η·√3·V·I·cosφ
to estimeate the absorbed power.
you can do the above calculations either