# What is the Starting PF to be entered for Motors?

The IEEE Brown book (Std 399) suggest that Motors under 1000 hp, have a typical PF=0.20, and Motors 1000 hp and over, have a typical PF=0.15. The Brown book also state that the starting power factor can be calculated by knowing the short-circuit X/R ratio of the machine.

Starting power factor = cos (arctan X/R).

In PTW, the above equation is used in generating the starting PF. The default X/R is 10, which will then result to a PF = 0.0995.

These power factor values are only rules of thumb, thus the actual power factor should always be confirmed with the manufacturer.

Starting power factor = cos (arctan X/R).

In PTW, the above equation is used in generating the starting PF. The default X/R is 10, which will then result to a PF = 0.0995.

These power factor values are only rules of thumb, thus the actual power factor should always be confirmed with the manufacturer.