The hydraulic system's drive system mainly has two types: pump direct drive and pump-accumulator drive. Pump Direct Drive The pump of this drive system supplies high-pressure working fluid to the hydraulic cylinder. The flow-regulating valve is used to change the direction of the liquid supply. The relief valve is used to regulate the defined pressure of the system and at the same time provide a safe overflow. The drive system has few links and simple structure, and the pressure can be automatically increased or decreased according to the required working force, thereby reducing the power consumption, but the maximum working force and the maximum working speed of the hydraulic machine are required to determine the capacity of the pump and its driving motor. This type of drive system is mostly used for small and medium-sized hydraulic presses, as well as large (such as 120,000 kN) free forging hydraulic presses that are directly driven by pumps.
Pump-accumulator drive There is one or a group of accumulators in this drive system. When the high-pressure working fluid supplied by the pump has a margin, it is stored by the accumulator; when the supply amount is insufficient, the accumulator supplements the supply. With this system, the capacity of the pump and the motor can be selected according to the average amount of the high-pressure working fluid, but since the pressure of the working fluid is constant, the electric energy consumption is large, and the system has many links and the structure is complicated. This type of drive system is mostly used for large hydraulic machines or to drive several hydraulic machines with a single drive system.