Page 29 - Fluid Power Engineering

6 Cha pte r O n e

converters are used where it is necessary to control the output torque
and develop a transmission ratio, other than unity, keeping accept-
able transmission efficiency.

1.2.5 Hydrostatic Power Systems
In the hydrostatic power systems, the power is transmitted by increas-
ing mainly the pressure energy of liquid. These systems are widely
used in industry, mobile equipment, aircrafts, ship control, and others.
This text deals with the hydrostatic power systems, which are com-
monly called hydraulic power systems. Figure 1.8 shows the operation
principle of such systems.
The concepts of hydraulic energy, power, and power trans-
formation are simply explained in the following: Consider a forklift
that lifts a load vertically for a distance y during a time period Δt
(see Fig. 1.9). To fulfill this function, the forklift acts on the load by a
vertical force F. If the friction is negligible, then in the steady state,

FIGURE 1.8 Power transmission in a hydraulic power system.

FIGURE 1.9 Load lifting by a forklift.