in industrial and agricultural production, the application of pump equipment can be seen everywhere, and many equipment also use pumps. the energy consumption of the pump is only second to that of the power motor equipment, which can be said to be a large energy consumption family. under the severe situation of energy conservation and emission reduction, reducing pump energy consumption is of great significance for energy conservation and emission reduction.
pumps mainly include centrifugal pump, turbine pump, mixed flow pump, axial flow pump, etc. the impellers of various pumps are on the motor shaft of the pump body. the rotation of the motor improves the liquid, and the motor is the most important part of the pump. the pump motor usually includes single-phase asynchronous motor and three-phase asynchronous motor, which is an induction motor. permanent magnet synchronous motor has been used for equipment power for nearly ten years. at present, cnc milling machines equipped with position encoders, servo motors on lathes and permanent magnet synchronous motors on injection molding machines are common. the machine tool adopts servo motor, which needs accurate positioning and mainly considers functions. the injection molding machine adopts permanent magnet synchronous motor, which is mainly installed to save energy and improve efficiency. the application of permanent magnet synchronous motor in other equipment is still relatively rare.
permanent magnet synchronous motor needs to support variable frequency controller, which is different from ordinary vector converter and dc variable frequency technology. it adopts the latest technology of hall-free dc brushless motor control such as mold control theory, adaptive technology, closed-loop control technology, etc. it can work at constant power, constant speed, constant torque, fast response speed, accurate control, flat output power curve in the whole power load section, and high motor efficiency, this is beyond the reach of other motors. permanent-magnet synchronous motor has high efficiency, which is much higher than the common power asynchronous motor, 15-20% higher than single-phase asynchronous motor (permanent magnet synchronous motor with variable frequency controller loss), and 7-10% higher than three-phase asynchronous motor. if the three-phase asynchronous motor is also equipped with frequency conversion control, the efficiency will be 11-15% higher, see the motor load characteristics table. in addition to the characteristics of the pump body structure, the efficiency of the pump is mainly the efficiency of the motor. the efficiency of the pump unit is higher when the efficient motor is used as the pump power. the general efficiency of the pump body is 50-70%. if permanent magnet synchronous motor with efficiency 10% higher than asynchronous motor is selected, the pump unit efficiency can be increased by 5-7%.
another characteristic of permanent magnet synchronous motor is that the higher the speed, the more obvious the advantages. its speed can be designed according to requirements. when the speed is high, the motor has small size, less consumables and low unit power cost. the speed of ordinary asynchronous motor is determined by the number of magnetic poles. usually 2 or 4 poles are used. when the speed of asynchronous motor is 50 hz, the maximum working speed of 2 poles is not more than 2900 rpm. the impeller of pump can only be designed according to this speed. if the speed is increased again, vector converter should be used to improve the frequency conversion speed of ac asynchronous motor. however, the volume and weight of variable frequency asynchronous motor are still not small, and the efficiency cannot be improved too much, which cannot be compared with the excellent performance of synchronous motor. according to the principle of fluid mechanics, vane pumps such as centrifugal pumps, vortex pumps, mixed-flow pumps and axial flow pumps can improve the head and flow. the flow is the first power of the speed increase, and the head is the second power of the speed increase. it can be seen that increasing the speed has a significant impact on improving the head and flow of the pump, and has great benefits for improving the performance of the pump. compared with traditional low-speed permanent magnet synchronous motor, high-speed permanent magnet synchronous motor has greater advantages in volume cost and performance.
improving speed is good for both aspects. how high the speed should be depends on the material technology. 4000-7000 rpm is generally selected. if the key materials and processing technology such as seals, bearings, shafts and impellers are well solved, especially impellers, rotors and shafts., with high concentricity, it can operate stably and without vibration at high speed, so higher speed can be selected. these goals can be achieved through routine efforts through equipment updating and processing process correction. the permanent magnet synchronous motor is equipped with a dc frequency conversion technology controller, which has automatic protection functions such as overheating, overcurrent and overload. the constant speed function of the synchronous motor keeps the flow and head of the pump unchanged when the grid voltage changes, and uses a wide voltage to maintain good working stability. the core of the digital processing circuit of the controller is the single chip computer, which can set various program descriptions, constant flow, constant pressure water supply, water level control, regular shutdown, communication with the computer host, online, office desktop remote control and network remote control according to the working needs of the pump, to realize the intellectualization and automation of the pump.
after the centrifugal pump, scroll pump, mixed-flow pump, axial flow pump and other high-speed permanent magnet synchronous motor matching pumps, the flow head and efficiency of the pump will be greatly changed, the head and flow will be greatly improved, the electromechanical integration is less, the volume is small, and the weight is light. the gradual application of permanent magnet synchronous motor in various pumps will bring industrial technological revolution to the pump industry, and raise the energy saving and emission reduction of the pump industry to a higher level. the energy saving effect of 10% is of great significance to the energy saving and emission reduction of the entire pump industry and even the whole country.