Power section assembly is the main component of the Downhole Motor.

Power section assembly consists of stator and rotor. Stator is made by squeezing rubber sleeve on the wall of steel tube. There forms spiral structure with a certain geometric parameter. Rotor is a crome-plated screw rod.

Stator and rotor matches with each other, to form spiral line and seal cavity through their guide rail difference. With rotor running in the stator, the seal cavity is moving along its axial direction, continuously forms and disappears to complete its energy conversion.

Motor torque is proportional to its pressure loss, but its outlet speed is inversely proportional to mud flow rate. With load increasing, screw drill speed decreases. Thus, pressure shall be controlled by the pressure gauge and flow rate shall be controlled by the flow rate gauge on surface. This way may control both torque and speed of downhole screw drill.