An electric hydraulic pump is a device driven by an electric motor designed to compress a fluid, typically a special grade of oil, used to actuate a secondary mechanism. Most of the pumps feature gear- or lobe-type internal pumping mechanisms and are typically run at relatively slow operational speeds. The electric hydraulic pump may be driven by alternating current (AC) or direct current (DC) motors depending on the application specifics. In most cases, the pump and motor form an integral unit with no external shaft runs and a flange-type joint between the two. A large range of pump sizes and capacities are available as off-the-shelf units or standard replacement parts for specific applications.
Hydraulic pumps draw fluid from a reservoir and send it at high pressure to a secondary mechanism as an actuation power source. The fluid is typically a specially-formulated, viscous oil used to actuate positive displacement mechanisms such as hydraulic rams and valve actuators. The fluid is pumped into a small, enclosed space in the secondary device's mechanism where it pushes against a rotary vane or a piston. The high fluid pressure causes the vane or piston to move, supplying a powerful actuation force in the process.
Most hydraulic pumps are lobe or gear types driven at moderated operating speeds by electric motors. Some pumps may run other sources such as compressed air or even hydraulic power such as high-speed water flows. The electric hydraulic pump is, however, the more common and efficient type. The motors used to drive the pumps may be designed for AC or DC power supplies, with the AC variants most commonly encountered in static, factory, or industrial installations and the DC types more commonly used on vehicles and other mobile installations.
The electric hydraulic pump is generally of one-piece construction consisting of a pump mechanism and motor joined with a flange type mounting arrangement. This type of design provides the most compact unit and is also the easiest setup to seal effectively against oil leakage and the ingress of dust and moisture. In some cases, the oil reservoir may be integral to the unit or a separate tank that feeds the pump via hoses or pipes. A large selection of electric hydraulic pump models are available, with smaller units generally featuring motors of approximately 1 horsepower (0.75 kilowatt) and pump outputs of around 1 gallon (3.75 liter) per minute at 100 bar (1,000 kilopascal) pressure. Large units may have motors of 14.75 horsepower (11 kilowatt) and deliver the oil at a rate of 13 gallons (50 liters) per minute at 100 bar (1,000 kilopascal) pressure.