Stirrer power in a homogeneous liquid

To operate a stirrer, knowledge is in the first instance required concerning the required power input Pm of the electrical motor. This has to take into account both the stirrer power and all power losses Py in the shaft bearings, in the gear box and in the shaft seals. In addition the start up power Pa has to be included. This considerably depends upon the stirrer type and upon the type of drive (stirrer shaft rigidly or elastically coupled with the motor shaft belt drive)  

Details over the start up power are e.g. available in [285, 333, 401], those over the power losses in the gear box, in bearings and in seals can be requested from the apparatus manufacturer. 

This section is solely devoted to the stirrer (shaft) power P. 

In order to determine the stirrer power P the torque and the stirrer speed n 

The torque can be measured e.g. electrically with a torsion shaft with strain gauges or eddy current transducers or mechanically with the swiveling motor. The stirrer speed is indicated by mechanical, electrical (photocell) or optical (stroboscope) instruments. 

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