Application of CT200 VFD in Cantilever Beam Pumping Unit

Production, distribution and refining applications in the oil and gas industry rely heavily on motor-driven pumps and pumping systems. Keeping electric motors driving critical operations at peak performance is vital to ensure maximum profitability. For continuous motor performance, engineers are focusing on variable frequency drive (VFD) and motor control technology. Because of their ability to regulate motor speed, VFDs are effective for controlling energy use.

Most oilfields in China have low efficiency and low production by using water or electric for oil, which causes electric cost account for  a large proportion in oil pulling costs. Resultly the oil industry is dedicated to pays much attention to electric saving.

Companies can gain energy savings by using VFDs to control flow by modulating motor speed. A 20 percent speed reduction can help save energy use by up to 50 percent, which means VFDs often quickly pay for themselves in energy savings. The higher the level of motor operating time and the larger the variation in load duty cycles, the greater the savings.

For the oil pumping units, to reform the motor drag system with the inverter is prime solution for energy-saving, advantages can be told as follows
(1) Raise power factor: power factor at input side can be enhanced to at least 0.9 from 0.25~0.5, significantly decreasing power supply current to lower the burden of the grid and transformer and circuit loss.
(2) Improve running efficiency: pumping speed of pumping units can be adjusted dynamically according to actual liquid supply capacity of oil well. Save energy and increase crude productivity.
(3) Realize real soft start: avoid overwhelming mechanical shock for motors, transmissions and pumping units, prolong devices use lives, reduce discontinued time and raise efficiency.
But some problems needed resolved when the inverter is used in oil pumping units, mainly the attack current and deal of renewable energy.

Shenzhen Dolycon Technology Co., LTD goes deep into the craft of oil pumping units, and develops specific software logic based on energy-power double close loop control which achieves continuous adjustment on output frequency and avoid motor electricity feedback and high bus voltage. This avoids braking units and energy feedback units.

The core of our solution is constant output power control. Based on PID control, the inverter achieves constant output power control by adjusting output frequency. Under the premise of meeting punching times, it decrease effectively average output power for energy saving and protection of oil pumping units.  Inverter needn’t set particular running frequency, actual output frequency is adjusted automatically by PID close loop control. In the down stroke, due to the large inertia of load, the synchronous speed is lower than the motor speed, the motor generates electricity, the inverter output torque is negative. In this case, the inverter automatically increases the output frequency to eliminate the negative torque to prevent the motor from generating power.

CT200 series variable frequency drive, based on DSP control system and equipped with leading sensorless vector control, can be applied in asynchronous motors and provide excellent drive performance and multiple protective methods. Independent duct design, hardware configuration and software functions of CT200 series greatly improve the convenience and environmental adaptability.