Oilfields direct drive screw pumpequipment is relatively simple. It consists of synchronous motor, screw pumpand motor speed control system, etc. which suitable for crude oil mining withhigh viscosity, high gas content, high sand content, high water content and lowproduction well. Overcoming the phenomenon ofgaslock and sand sticking,etc. effectively，it has small coversarea，high efficiency andgood superiority of increasing productivity and energy saving advantages.

1.Brief introduction of screw oil pump  

The screw pump is a positive displacement rotor pump, which depends on the volume change of the seal cavity formed by the screw and the liner to suck and discharge the liquid. Screw pumps are divided into single screw, double screw, triple screw, five screw pumps and so on according to the number of screw. Oilfields direct drive screw pump equipment is relatively simple. It consists of synchronous motor, screw pump and motor speed control system, etc. which suitable for crude oil mining with high viscosity, high gas content, high sand content, high water content and low production well. Overcoming the phenomenon of gas lock and sand sticking, etc. effectively ， it has small covers area，high efficiency and good superiority of increasing productivity and energy saving advantages.

2.Technological process and requirements

Requirements: low operating speed, large torque, non-inrush when screw rotating, controlling reverse speed and smoothly releasing reverse torque function available when start and stop, high efficiency etc. In addition, requirements of application as below:

2.1 Simple operation and visual monitor;

2.2 Large start-up torque and high efficiency；

2.3 Start-up stable, with open-loop vector control, identifying motor magnetic pole position automatically and making output current smaller under same torque value.

2.4 When stop, the inverter software releases the reverse torque of screw automatically.

3.The solution of ENC EN650C special inverter for oil pump

EN650C inverter is specially developed for the direct-drive screw pump of oil field. The direct drive screw pump is driven by synchronous motor with simple equipment composition. It has high working efficiency, small covers area, high energy saving efficiency and can overcome the phenomenon of gas lock and sand sticking. It is not sensitive to motor parameters and does not depend too much on the variation of parameters. It also has strong resistance to environmental temperature change, quick and stable response to high-speed stop. The Acc/Dec time can reach 0.1s.

In the direct driving equipment, the power range of synchronous motor is 7.5 ~ 37KW commonly. The direct driving equipment consists EN650Cdirect-drive type oil pump special frequency inverter which built-in special direct drive software, brake components, reverse rotating protection components at stop, temperature control system, monitoring system, etc.

4. Advantages of the application

1.Simple operation and visual monitor;

2.Support field-oriented control of different type PMSM with large start-up torque and high efficiency;

3.Start smoothly, the detection of the motor initial magnetic pole position function available;

4.Anti-reverse protection during stop progress; It detects the reverse torque on the current screw rod automatically and control the screw rod reverse rotating at low speed to release the torque.

5. Parameters setup

6. Pictures of EN650C special frequency inverter field application