BOOK IN SERIES
“ This article has been excerpted from the textbook“ Electro-Hydraulic Components and Systems”
ISBN: 978-0-9977634-2-3
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Hydraulics Versus Electrical Systems- CHAPTER 1
Author Dr. Medhat Khalil
1.1.2.5- Energy Storage Elements( Capacitive Elements)
Each of the two systems has Capacitive Elements of different sizes to store energy. As shown in Fig. 1.14, Capacitors( 1) or Batteries( 2) are used to store electrical energy. Accumulators( 3) are used to store hydraulic energy. The amount of stored energy and the charge time is proportional to the size of the capacitive element in both systems. It is known for fact that electrical capacitive elements have larger Energy Density than hydraulic accumulators. effort variable across the element in order for flow to pass through the element in the forward direction. Minimum Cracking Pressure is required to open a check valve. Barrier Voltage is required to open the diode.
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Figure 1.15- Non Return Elements
Figure 1.14- Energy Storage Elements
1.1.2.6- Non-Return Elements
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Each of the two systems has a Non-Return Element of different sizes to prevent flow in the reverse direction. As shown in Fig. 1.15, Diodes( 1) are used in electrical systems and Check Valves( 2) are used in hydraulic systems. Both diodes and check valves require a minimum value of the
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1.1.2.7- Electrical versus Hydraulic Power Control Elements
From what has been previously discussed, electrical control elements have the following advantages over the hydromechanical valves:
• Controllability: because of the digital control capabilities, electrical control elements perform expanded, reprogrammable and smarter control functions than hydro-mechanical valves.
• Closed-Loop Control: hydro-mechanical components can’ t be used to build closed loop control system with electrical feedback. They can perform limited closed control with mechanical feedback such as in pressure compensated, power limited and load sense pumps.
• Size: electrical control elements are smaller in size for the same power.
• Material: electrical control elements are produced from less amount of material.
• Production Process: electrical control elements require less physical production process. Hydraulic valves require casting, machining, forging, heat treatment, etc.
58 Global MDA Journal may 2018