permanent magnet motor of the beam pump machine

The report of permanent magnetization of the asynchronous motor of the kowtow machine

At present, the commonly used pumping unit in oil field production is a kowtow unit (also known as a beam pumping unit), which is composed of a donkey head, a beam, a support, a reducer, a rocker arm, a connecting rod, a frame, and an asynchronous motor. The load rate of asynchronous motors for pumping units during normal operation is very low, generally about 20%, and the load rate is only about 30%. Asynchronous motors have low power factor, low efficiency, and large electrical energy waste when operating at low load rates. Pumping units are a big energy consumer in oil fields, and their electricity consumption accounts for about 40% of the total electricity consumption of oil fields. Their system efficiency is very low. According to surveys, they are generally less than 30%, and some are even below 5%. According to the latest statistics, the operating efficiency of pumping units is particularly low. The average efficiency in my country is 25.96%, which means that more than 70% of the energy in the entire system is used for wasteful work, resulting in high electricity costs for oil well mining. Energy waste is very serious, therefore, the energy saving potential of pumping units is very considerable.
Second, the transformation plan
According to the current status of the drive system of the traditional kowtow machine, we have introduced a permanent magnetization modification plan for the asynchronous motor. That is, the drive mode of frequency converter + permanent magnet synchronous motor is used to replace the traditional asynchronous motor, but the belt, reducer and other mechanisms are still retained.
3. Advantages
1. The system efficiency can be increased by 5-10%.
The air gap magnetic field of the traditional asynchronous motor is generated by the stator current. Due to the existence of this part of the current, the efficiency and power factor of the motor become low. The air gap magnetic field of permanent magnet synchronous motor is no longer established by stator current, but is formed by high-efficiency permanent magnets, making the efficiency of permanent magnet synchronous motor 5-10% higher than that of asynchronous motor. At low speed and light load, the efficiency and power factor of asynchronous motors are lower, while permanent magnet synchronous motors still maintain high efficiency and power factor at low speeds and light loads.
2. The permanent magnet synchronous motor has large starting torque, stable starting without impact, and stepless speed regulation can be realized.
The starting torque of permanent magnet motors can reach more than 2.5 times the rated torque. The starting is stable, no impact, and the equipment damage rate is extremely low. According to the requirements of oil wells, stepless speed regulation can be realized, and the system has good low-speed performance.
3. Save the purchase and maintenance costs of reactive power compensation equipment.
The power factor of the permanent magnet synchronous motor used in the pumping unit can reach more than 0.9 under any load, which can greatly reduce the absorption of reactive power from the power grid, save the purchase and maintenance costs of reactive power compensation equipment, and improve the quality of the power grid.
4. The transformation is simple and easy, and the cost is low, and energy-saving benefits can be realized immediately.
The transformation only needs to replace the asynchronous motor with a permanent magnet synchronous motor and add a frequency converter at the same time. The transformation is simple and easy, and the transformation cost is low.
5. Take advantage of national policies.
Permanent magnet motors conform to the country's industrial policy for vigorously developing energy-saving and environmental protection industries, and have important practical significance for promoting the development of a circular economy and a low-carbon economy. Liaoning is an old industrial base characterized by the equipment manufacturing industry. By improving traditional equipment with advanced technology, the technical content and competitiveness of products can be improved, and the sustainable development of the industry can be promoted.
Fourth, the cost of permanent magnet motors
Compared with asynchronous motors, the cost of permanent magnet motors generally needs to be increased by about 30%, and the increased costs can generally be recovered within 1-2 years using the saved electricity bills.
5. Reliability of permanent magnet motor
Permanent magnet synchronous motors have the characteristics of high efficiency, energy saving, reliable structure, and environmental protection. They have been widely used in industries such as elevators, electric vehicles, oil fields, injection molding machines, machine tools, warships, submarines, and rail transit.
According to statistics from the Elevator Association, as of 2018, more than 5 million permanent magnet synchronous motors have been used in elevators. As of 2018, there are 2.61 million electric vehicles in China, and the state plans to have 5 million electric vehicles in big cities by 2020. Most of the electric vehicle motors in our country use permanent magnet synchronous motors. It can be seen that permanent magnet synchronous motors are absolutely reliable when used in automobiles. The operating conditions of automobiles are far worse than those of oilfield kowtows, so permanent magnet motors are absolutely no problem when used in oilfield kowtows.
Permanent magnet motors are used in Daqing Oilfield, Panjin Oilfield, Shengli Oilfield, Dagang Oilfield, etc. It is understood that some permanent magnet motors in Daqing Oilfield have been in operation for more than 15 years.
In warships and submarines at home and abroad, MW-class permanent magnet synchronous motors are all in service, including high-speed rail and other rail transits are also using permanent magnet synchronous motors, which further illustrates the high reliability of permanent magnet motors. The permanent magnet motor is the future development trend.
Six, summary
The permanent magnetization scheme of the traditional kowtow machine drive system has the advantages of high efficiency, energy saving, high reliability, large starting torque, smooth starting and no impact. At the same time, the purchase and maintenance costs of reactive power compensation equipment can be saved. The transformation of the scheme is simple and easy to implement, the transformation cost is low, and energy-saving benefits can be realized immediately.