But first I need to be able to measure the electrical power coming into the motor as at the end I'm also interested in evaluating the efficiency of the unit.

What I've done so far is to measure the input current with a clamp meter and the voltage with a multimeter.

How do I go about to evaluate/measure/estimate the Power Factor?

For equipment I have multimeters, RPM meter, oscilloscope (voltage probes only) and an old power meter that I have not taken the time to check or read the specs.

If I use the power meter, would I need to take any special precautions when connecting it to the motor? I'm not sure if the inductive nature of the motor could damage the power meter...?

After this is figured out I will apply a Belt Brake to measure the actual mechanical power delivered by the motor, hopefully I get a figure close to 3HP.

I'll appreciate any suggestions.

Regards.

Dan