Calculating power consumption

[who took my fluke?]

I have a 415, 55kw motor running at 30 amps for the best part of 12 hours a day. If i am to calculate the power consumption, what equations would i use;

if i use P = 1.73 x 418 (measured) x 30 xPF x efficiency

what values would i use for efficiency and PF, i thought these values change with load and condition of motor? maybe wrong though!!

thanks

the reason i am doing this is to justify installation of a VSD

 

[Spark123]

If you are measuring it directly then the total consumption of a star connected motor can calculated, using a PF of 0.8 as a guide by:
P = 3 x Vp x IL x PF
P = 3 x (415/root3) x 30 x 0.8
P = 17.28kw
If you want to know the true PF you will need to connect a PF meter.

The efficiency is given as a % by (output power / input power)* 100, what is the kw output of the motor?