Page 32 - Fluid Power Engineering

Intr oduction to Hydraulic Power Systems 9

FIGURE 1.11 Hydraulic system circuit, schematic, and symbolic drawings.

1.4 The Advantages and Disadvantages of Hydraulic Systems
The main advantages of the hydraulic power systems are the following:
1. High power-to-weight ratio.
2. Self-lubrication.
3. There is no saturation phenomenon in the hydraulic systems
compared with saturation in electric machines. The maxi-
mum torque of an electric motor is proportional to the electric
current, but it is limited by the magnetic saturation.
4. High force-to-mass and torque-to-inertia ratios, which result
in high acceleration capability and a rapid response of the
hydraulic motors.
5. High stiffness of the hydraulic cylinders, which allows stop-
ping loads at any intermediate position.
6. Simple protection against overloading.
7. Possibility of energy storage in hydraulic accumulators.
8. Flexibility of transmission compared with mechanical systems.
9. Availability of both rotary and rectilinear motions.
10. Safe regarding explosion hazards.
Hydraulic power systems have the following disadvantages:

1. Hydraulic power is not readily available, unlike electrical.
Hydraulic generators are therefore required.