Page 26 - Fluid Power Engineering

Intr oduction to Hydraulic Power Systems 3

FIGURE 1.2 The classifi cation of power systems.

FIGURE 1.3 An automotive drive train.

shaft of the gear box turns at the same speed as the engine. Its out-
put shaft (4) turns at different speeds, depending on the selected
gear trans mission ratio. The power is then transmitted to the wheels
(8) through the universal joints (5), drive shaft (6), and differential (7).
When compared with other power systems, mechanical power
systems have advantages such as relatively simple construction, main-
tenance, and operation, as well as low cost. However, their power-to-
weight ratio is minimal, the power transmission distance is too limited,
and the flexibility and controllability are poor.

1.2.2 Electrical Power Systems
Electrical power systems solve the problems of power transmission
distance and flexibility, and improve controllability. Figure 1.4 illus-
trates the principal of operation of electrical power systems. These
systems offer advantages such as high flexibility and a very long
power transmission distance, but they produce mainly rotary motion.
Rectilinear motion, of high power, can be obtained by converting the
rotary motion into rectilinear motion by using a suitable gear system