Ring Spinning
Compacting is bought in watts per spindle, and it runs every hour the frame runs.
— kW
At the motor terminals, for the whole frame
The power calculation is the ideal fan law and assumes the stated pressure is the total the fan develops against the system. Real installations lose pressure in the ducting between fan and spindle, so the fan pressure entered should be the measured value at the fan rather than the design value at the spindle; using the latter understates the power substantially on a long frame. Fan efficiency is the aerodynamic efficiency at the actual operating point, not the peak on the fan curve - a fan running well off its best-efficiency point can be twenty points below its rating. Airflow per spindle is a design figure and assumes no leakage; a worn or damaged suction tube draws more air at less useful compacting. Energy costs here are compacting only and exclude the spindle drive, the drafting drive and the overhead cleaner.
Compact Spinning Suction Airflow, Fan Power & Energy Cost — free, with the formula and a worked example, at Textile School.