Precise Pressure Control with Variable Speed Drive of Hydraulic Pump

Precise Pressure Control with Variable Speed Drive of Hydraulic Pump

Precise Pressure Control with Variable Speed Drive of Hydraulic Pump

Precise pressure control is carried out in many industrial applications such as holding parts/apparatus in machine tools, cylinder testing stations, driving, crushing, plastering and compression operations. Pressure control can be done with manually adjustable valves, or with proportional valves in places where variable pressure is needed. In this type of controls, the excess oil required for the required pressure is returned to the tank under pressure through the safety valve in the system. Therefore, heat energy will be released and the oil in the existing hydraulic tank will heat up, and additional power and equipment will be needed to cool this oil. The energy loss in these systems is quite high.

In variable speed drive application, enough oil flow is sent to the system to create the required pressure. The constraint here is to rotate the pump speed between the minimum and maximum allowable speeds. Depending on the pump type, inability to produce efficient suction at lower speeds, overheating of the pump or

Different problems such as pulsation may occur in the pressure line. At higher speeds, additional precautions are needed to prevent the suction line pressure from falling below the pressure value determined for the pump.

Precise pressure control can be achieved within the requested pressure ranges by rotating the pump within the minimum and maximum allowed speed ranges and using appropriate orifices.

The resistance that occurs during flow due to the narrowing of the area at the orifice entrance creates a pressure difference. By using Bernoulli and continuity equations, the orifice flow equation is found as follows. In order to control pressure in different value ranges, the orifice diameter selection that should be used depending on the pump displacement to be used can be determined by the orifice flow formula (1).

This entire paper can be found in Chapter IX. It can be accessed from the NATIONAL HYDRAULIC PNEUMATIC CONGRESS proceedings book.