Planetary gearbox efficiency

planetary gearbox efficiency , Power losses in gear systems are associated primarily with tooth friction and lubrication churning losses.    Churning losses are relatively independent of the nature of the gears and the gear ratios - planetary gear are primarily realated to the peripheral speed of the gears passing through the fluid.  Churning losses are difficult to calculate and estimates based on experience are often used in initial gear design.   The frictional losses are related to the gear design,the reduction ratio,the pressure angle, gear size, and the coefficient of friction.