At present, the screw pump widely uses the drive mode with an electric motor belt transmission reducer. Although it can produce stably and effectively, some problems still exist, such as low transmission efficiency for gear reduction, large equipment volume, high failure rate, large noise, bad reliability as well as parameter adjusting operations are troublesome.

The ground drive system of the direct drive screw pump with permanent magnet brushless DC motor developed by our company has the advantages including stable operation, good effect of energy saving, low operation expense, low noise, convenient management extremely minimum maintenance work, etc., after nearly two years of operation.

The main technical indexes of the ground system of the direct drive screw pump with electric motor produced by our company are as follows:

Power Factor of the Electric Motor 95%

System Efficiency 90%

Rated Temperature Eising 55℃/131°F (Rated load, continuous work)

Starting Torque: Three times of the rated torque per minute

Adjustment Range of the Rotation Speed: 0-100% rated rotation speed

The Intelligent Controller is composed of three parts including rectifying wave-filtering, intelligent calculation logic control & power unit.

The direct drive screw pump developed by our company has the following characteristics:

1. The structure of the transmission system is simple, reasonable, high efficient. It can save energy by 30%.

The structure of the ground drive system of the direct drive screw pump is very simple, reasonable and has high efficient transmission. The direct drive screw pump abolishes the reducer belt transmission equipment of the traditional mechanical screw pump. The motor adopts a vertical hollow axis structure. The transmission formed between the motor and the screw pump is direct co-axisconcentricity transmission with the nearly 100% efficiency, which increases the mechanical efficiency of the whole system by 30%, decreases the failure rate of the machine by 90%, decrease the maintenance work by more than 90%, thus prolongs the life of the equipment and decreases the operation cost a lot.

2. Specially designed direct current permanent magnet brushless torque motor with high efficiency low speed, high power factor

The direct current permanent magnet brushless torque motor, witch adopts the rare earth permanent magnetic rotor with high field intensity, has high power factor. It is 5%-12% higher than the asynchronous motor with the same volume. The motor has the advantages of large torque, small volume, light weight. The properties liability have been greatly improved.

3. The starting torque of the low-speed direct current permanent magnet brushless torque motor is large. Starting power reserves are not needed.

The low-speed direct current permanent magnet brushless torque motor has the characteristic of constant torque with the starting torque being 3 times of the rated torque per minute. It corresponds with the starting characteristics of the screw pump is in favor of the cost reduction. In comparison with the asynchronous AC motor, the energy saving effect is 2-5%. The motor has soft external characteristics the starting torque reaches 3-4times of the rated torque, which has incomparable advantage over other products of asynchronous AC motors.

4. Low lossless heat of the motor

The motor adopts high-quality iron core material and optimized magnetic circuit structure winding design. It reduces the copper and iron loss as much as possible under the condition of giving attention to the cost. Many measures have been taken which make the energy saving effect of the system reach 20-40% and the temperature rising no higher than 55℃.

5. Anti-reversion by electromagnetic hamper dynamic braking

Combining with the traditional braking unit, the anti-reversion control algorithm by electromagnetic hamper originally created by our company realizes the electronic anti-reversion control. It releases the elastic torque of the sucker rod slowly and completely,which is helpful for the start-up of the system. Meanwhile, it also improves the safety performance and can effectively avoid the occurrence of mechanical accident such as crack of the pump rod.

6. Heat dissipation anti-reversion control of the electric motor with large torque system

The DC motor still adopts the structure without fan. We carried out the optimal design selection of the magnetic circuit, groove type, winding data, iron core material for the electric motor, carried out the optimal design for heat reduction with the reinforcement of the heat dissipation effect. In aspect of anti-reversion control, we created initially substitution type anti-reversion control mode, that is, electromagnetic hamper braking unit dynamic braking which makes the anti-reversion system more reliable.