Downhole motor is a type of positive-displacement downhole motor (PDM). After high pressure drilling fluid(or Compressed gases) enters into by-pass unit, pushes disc insert closing by-pass hole and allowing all Down-hole Motors mud to flow to motor, fluid pressure forces rotor to rotate that transfers torque to bit to achieve drilling purpose.

Components of Downhole Motor and their functions
Main components of a downhole motor assembly are as By-pass valve unit, Falling-off –proof device, Motor unit, Cardan shaft unit (There are two options: petal and flexible shaft structure types) and Transmission shaft unit.


1. By-pass valve unit
By-pass valve unit is fixed on the top of a downhole motor, its functions are: a) To allow drilling fluid to
enter into drill pipe while running in to reduce running-in resistance. b) To make drilling fluid go to annular
while pulling out to avoid drilling fluid overflow on wellbay. Upon starting of mud pump, high pressure mud via by-pass unit pushes disc insert downward, compressing spring, closing by-pass hole and allowing all mud to flow to motor. After shutdown of mud pump, under the action of spring, disc insert moves upward, opening by-pass hole and allowing drilling fluid to inter into drill pipe or flow from drill pipe to annular via by-pass hole.
2. Falling-off-proof unit
Although downhole motors of our factory have adequate strength to meet requirements of well drilling, a few accidents still take place. This is somewhat decided by the nature of the working environment. In order to reduce the loss of customers resulted by accidents to minimum, all models of our factory are equipped
with falling-off- proof device.
There are two kinds of falling-off-proof device. The first is falling-off-proof nut for transmission shaft. All models of downhole motors are equipped with this nut mainly to avoid transmission shaft's abruption and falling down to downhole. The second is shell falling-off-proof device, which is set on the top of rotor, designed mainly for complex steerable downhole motor assemblies. This device will not be provided if customer does not require it in particular. (Special notice: When a customer services a downhole motor with falling-off-proof device, he should first remove by-pass valve unit, then remove falling-off-proof device, and finally remove other parts in order.)
3. Motor units
Motor unit is Multi-level displacement and the core of downhole motor assembly, its function is to convert the energy of high pressure fluid into mechanical energy to make bit rotate, consists of two parts: stator and rotor.
4.Cardan shaft unit
This unit consists of the housing and flexible shaft. The action of cardan shaft is to convert planet motion of a rotor to fixed-spindle rotation of transmission shaft. It joins motor and transmission shaft together and transfers motor-provided rotating speed and torque to transmission shaft and bit. We can supply two structure types of cardan shaft, petal type and flexible shaft type.
5. Transmission shaft unit
Transmission shaft unit is fixed on the bottom of a downhole motor The action of transmission shaft is to transfer motor generated torque to bit. The core components of transmission shaft are axial thrust bearing and radial combined bearings; the two bearings bear the pressure generated by drilling axial and radial load
simultaneously.

In addition, in order to meet the drilling process needs, our company can provide with a different structure with the diameter of the stabilizer. Of its stabilizer has the following several types:
1. Single straight edge asymmetric centralizer;
2. Three straight edge asymmetric centralizer;
3. Three spiral centralizer;
4. Four spiral centralizer; 5. Five straight edge cntralizer.