The most important thing for ultra-efficient motors is the degree of process assurance. The process of continuous improvement of motor efficiency is the process of continuous upgrading of products, and it is also a symbol of the comprehensive level of a country’s motor industry.
The key point of high-efficiency motor design is to reduce various losses and improve motor efficiency. The measures taken include: applying special off-line tools to improve the full rate of stator slots and increase the cross-sectional area of copper wires; improve manufacturing accuracy, shorten the length of coil ends, and strengthen the manufacturing quality of punching sheets and stator cores, thereby reducing iron loss and excitation current and the copper loss caused by it; improve the rotor slot insulation process to reduce the load miscellaneous loss; reasonably select the grade of the silicon steel sheet to reduce the iron loss and stator copper loss.
1. Influencing factors of motor efficiency
Motor losses include stator and rotor copper losses, iron losses, mechanical losses, and stray losses. There are many ways to reduce motor losses and improve efficiency:
Measures to reduce stator copper loss mainly include reducing stator resistance and shortening the length of winding ends; thinning insulation, increasing slot fill rate, increasing wire cross-sectional area, and using new materials to reduce the resistivity of magnet wires;
The measures to reduce the aluminum consumption of the rotor mainly include the use of a large cross-sectional area of the rotor slot shape and the increase of the end ring cross-section, improving the purity of aluminum, and reducing the rotor resistance, etc.;
The measures to reduce iron loss mainly include using low-loss high-quality cold-rolled silicon steel sheet to reduce the eddy current loss of the motor; adjusting the groove shape and selecting a reasonable magnetic flux density to reduce the fundamental iron loss; increasing the length of the iron core and reducing the magnetic flux density to reduce the loss ; Measures to improve the quality of iron core manufacturing and ensure the insulation of the silicon steel sheet surface;
Measures to reduce mechanical consumption mainly include high-efficiency fan structure and reasonable air path, improving blade surface roughness, making air flow smooth, improving fan efficiency, and reducing wind friction; selecting high-quality low-friction bearings, grease, and reducing friction loss; improving shape. Bit tolerance accuracy, to ensure the assembly quality of the motor, reduce friction loss, etc.;
Measures to reduce stray loss mainly include the use of multiple slots in the stator slots, reducing the width of the stator and rotor slots, and using non-magnetic materials at both ends of the iron core; using “sine” windings to weaken higher harmonics in the magnetic field and reduce additional losses , Appropriately increase the air gap, the rotor adopts fewer slots, adopts magnetic slot wedges, precisely controls the degree of chute, and adopts measures such as special chute.
2. Key manufacturing technologies to reduce motor loss
2.1 Technical measures to reduce mechanical consumption
The size of the parts adopts the intermediate tolerance and improves the accuracy of the geometric tolerance to ensure that the parts are not deformed during transportation and assembly, and at the same time to ensure the assembly quality of the motor, thereby reducing friction loss. Production experience shows that the use of bearing chamber rolling process can effectively improve the machining accuracy of bearing chamber matching parts and reduce a series of problems caused by bearing running accuracy; the online quantitative oil injection technology of bearing grease can stably control the grease injection. The number of people ensures that the high-efficiency motor and the mechanical consumption of mass production are stable.
The bearings of small and medium-sized motors generally use rolling bearings and use suitable high-quality lubricants. The traditional process method is to manually apply lubricating grease in the bearing before the bearing is assembled, then assemble the bearing, and finally use the oil gun to re-grease the motor. The problems of this method of manually adding grease are as follows: the amount of application is not easy to control, which affects the lubrication of the bearing parts and mechanical wear; the lubricating grease is easily contaminated, and there is oil around the motor parts after manual wiping; there are many processes, Operation is inconvenient.
There is currently no device capable of quantitatively filling the motor with oil. In order to effectively control the amount of grease added, after a large number of technical verifications, it is determined to use automatic grease filling machines, oil pipes, quick-change joints, etc. to realize automatic quantitative oil filling of motor online assembly. In this technology, the oil filling machine is installed at the bottom of the motor assembly line. The motor does not need to be filled with grease during the assembly process. When the motor is offline, the quick-change joint of the automatic quantitative oil filling device of the assembly line is connected to the motor oil filling pipe, and the oil filling machine can be started. Grease the motor automatically and quantitatively. This device has the advantages of convenient use, accurate quantification, high efficiency and quickness, and is currently widely used in high-efficiency motors and other motors, and has obtained a national utility model patent.
2.2 Technical measures to reduce stray loss
The rotor outer circle generally adopts the turning process in the motor manufacturers. Due to the influence of the notch aluminum strip, turning alternately from hard silicon steel sheet to soft aluminum, due to poor machine tool precision, the rotor outer circle is dimensionally unstable after machining. If one-tool turning is used and some rotor outer diameter machining allowance is small, the surface quality of the outer diameter of the rotor will be poor, the burr will be large, or the adhesion between the rotor surface sheets will be serious, resulting in large motor miscellaneous consumption, temperature rise, and low efficiency. Therefore, it is particularly important to standardize the machining process, parameters, and quality inspection standards of the rotor cylindrical turning.
The magnetic field commutation frequency of the rotor is very low, and the hysteresis loss and eddy current loss generated by the rotor silicon steel sheet itself can be ignored. It needs fine turning, roasting, and special treatment of the outer circle to increase the resistance between the outer circle bar of the rotor and the punching piece, the punching piece and the punching piece, and reduce the stray loss caused by the lateral current. Through the analysis, new tools and processes can be popularized and applied in the rotor finishing.
Most manufacturers use a 450 positive offset knife when the outer circle of the rotor is turned, and the inclination angle of the blade is positive. Under the same cutting parameters, the axial component force of the knife is large, which is easy to reverse and stick the silicon steel sheet. The new process uses a 930 positive-biased Sandvik machine to clamp the tool. Because the axial component of the tool is small, it can reduce the rewinding and adhesion of the silicon steel sheet, and can effectively improve the surface processing quality of the rotor.