The effective drive torque M 1eff on the pump shaft is greater than the theoretical drive torque M 1th by the moment losses M 1V (Figure V 13 a):
In the case of the motor, the effective displacement flow Q 2eff is formed by the sum of the theoretical displacement flow Q 2th and the leaked oil Q 2L:
The moment created M 2eff is M 2v smaller than the theoretical (hydraulic) moment M 2th (b):
Figure V 13: Moment losses in hydraulic pumps (a) and (b) hydraulic motors
Losses in hydrostatic displacement machines are comprised of the leakage losses in the displacement elements and the control surfaces (summarised in the volumetric efficiency η Vol) and moment losses, which are summarised in the hydromechanical efficiency η hm.
The effective delivery flow Q 1eff (flow rate at the pressure connection) of a pump is smaller than the theoretical drive rotation speed Q 1th by the leakage losses Q 1L (product of drive speed and displacement volume):