Primary control

In a hydrostatic transmission, the pump can be adjusted and the motor is associated with constant displacement. The drive rotation speed is therefore proportional to the flow rate for the pump, i.e. the adjusted displacement volume. This would result - at constant pressure - in a (theoretically) constant torque, with power increasing to the maximum level (Figure P 16). The resulting adjustment range for rotation speed is as follows:

while the torque ratio would be:

with the displacement V 2 remaining constant (see also secondary control).

Figure P 16: Options for converting transmission in relation to current-fed systems. a) = pure primary control; b) = pure secondary control; c) = composite control