Design And Research Of Direct Drive Permanent Magnet Motor Drive Controller Based On Pwm Technology Of The Screw Pump

In China, screw pump, petroleum exploitation equipment, as small in size and low in one-time investment, is applied widely in various major oil fields. But the conventional mechanical screw pump driving system has kinds of problems, such as the moment of force cannot be controlled, so when there's anything goes wrong under the well or the pipeline on the ground goes jammed, the speed of the pump cannot be reduced or changed, which result in twisting off the pump rod, cracking the gear wheel in reducer, and damaging the motor.In order to solve these problems, we are trying to develop new type pump with a directly driven rod. It is advanced from the mechanical one, removing the mechanical part driven by the strap,driving screw pump directly. This directly driven screw pump system can be very efficient in production and economical in power consumption and also prevent the mechanical accident including the break-ff of pump rod effectively, thus extending the working time but lessening the labor intensity. It has a promising future.This new system uses brushless direct current controller and three- phrase brushless controlling mode, which can control the moment of force exactly. When the moment increases and passes over the fixed point, the controller will slowdown and use the maximum limitation mode to control. if there's sand blocking underground temporarily, the controller permits the motor to produce the moment force twice or one and a half of the fixed amount for one to two minutes. The controller also can identify the situation such as insufficient loaded or even there's no oil in the pump.In addition, this system is armed with soft brake technology, which realizes a reliable stop of the machine, prevents the inversion, and avoidsthe releasing of sucker rod, mechanical damage and even physical injury. Soft brake technology belongs to restrained controlling mode. It is installed energy consumption resistance and unattached brake controller inside the controlling case. When the motor is stooped or electricity in system is cut off, the pump rod will release its elasticity, pulling the magneto inductor to reverse, thus connecting the brake resistance. The more the acceleration of the reversion has, the bigger the restraining force from electricity generation is, which finally dive the pump rod to the initial status. So when the next time the screw pump operates the initial moment will be very small and it will be more easy to start up and the inversion in building well will not occur.Because screw pump controller is similar to transducer, there's no need to install another transducer. The operation is simple and intuitive and easily managed on the site. The workers can adjust constantly the working speed of the pump via human-computer interface of controller, monitoring directly the running condition. Compared with the conventional speed control by changing the size of strap, this new pump is obvious superior.