A Hydraulic Power Unit like the ones from https://www.hydraproducts.co.uk/Hydraulic-Power-Units/Standard-Power-Units can be used in a variety of different ways. They are essentially a unit that is self-contained and has a motor, a pump and a fluid reservoir all included in the unit. These kinds of units are often used when hydraulic pressure is needed to run motors and cylinders and this is usually on construction sites and other industries where portable units are needed.
Any hydraulic system uses fluid to create and transfer energy to another force or motion. This could be a linear motion or a rotary motion or other force that is needed and it will depend on what the motor or cylinder in the equipment being used is designed to do.
You can find the units in a number of different sizes and the one you need will depend very much on the pressure capacity or power that is needed to create the hydraulic action that is needed for the equipment that you are using. The size of the fluid reservoir will also determine what pressure can be built up when the hydraulic pump is activated.
The fluid in the tank is pumped into the accumulator area and this continues until the desired pressure is reached. At this stage a valve switch then starts the pumping action that will circulate the fluid throughout the accumulator. This flow then powers the pressure that is needed to make the power unit function effectively.