According to the general classification of pumps, rotary pumps are divided into two large groups: rotary and piston pumps. They relate to the positive displacement pumps, the operating principle of which is to change the volume of the working chamber. The pumped liquid fills the working chamber and is then pushed out into the discharge nozzle. The working chamber is a temporarily created space limited by the rotor and stator of the pump and changing its volume during the operation of the pump. Moving of the movable parts provides a change in the volume of the working chamber and, as a consequence, pumping the medium.