(1) Adjust the motor fan to reduce mechanical loss
First, let's look at how to save energy by changing the size of the fan: Everyone knows that the motor is a device that converts electrical energy into mechanical energy. During the conversion process, losses are generated. These losses occur in the form of heat, which causes the motor to heat up. The stator winding has a copper loss after the current flows, and the heat is transmitted to the stator core through the slot insulating material, and then transmitted from the stator core to the motor casing to the space. The heat of the rotor is generated by the aluminum consumption of the rotor and its friction. It is transmitted to the rotor core and the inner fan surface. The internal fan is stirred to dissipate the heat in the inner space of the motor, and then transmitted to the stator core, the end cover and the base. Both the stator and the rotor are blown away by the external fan. Therefore, the amount of external fan air volume is the key to determining that the temperature of the motor cannot exceed the temperature allowed by its insulation grade.
The national standard stipulates the allowable temperature rise of the motor of various insulation grades under the rated operating conditions. It is required that the hottest temperature of the motor is not allowed to exceed the limit temperature of the insulation grade, and the common insulation grade of the motor is as follows:
Among them: allow temperature rise = allow temperature limit ambient temperature specified value hot spot temperature difference
The hot spot temperature difference of the winding refers to the difference between the stable temperature of the winding hot spot and the average temperature of the winding when the motor is rated.
When the motor is at no load or light load, the total loss of the motor is smaller than the rated time, and the air volume is proportional to the total loss of the motor, so the fan is in the big horse car (because the ventilation loss and the motor speed are constant, the ventilation loss does not follow the load) Change, so the air volume should be reduced to reduce the ventilation loss of the motor). Changing the shape of the fan blade can reduce the air volume, but it is more troublesome. It is better to reduce the diameter of the outer fan blade to reduce the air volume. We know that the mechanical loss of the fan itself is proportional to the 45th power of the blade diameter, and the air volume is proportional to the square of the fan blade diameter. Therefore, when the fan blade diameter is reduced, the air volume is not much reduced, and the ventilation loss is much reduced.
As the cooling air volume of the external fan is reduced, the temperature rise of the motor is increased, but the temperature rise of the motor can be maintained within the allowable range of the insulation level. At the same time, we also need to see that the motor loss of the motor is reduced due to the reduction of the outer blade diameter, which will further reduce the temperature rise of the motor. Especially for motors with high speed of 2, 4 grades, when the outer diameter of the fan is reduced by 14% and 16%, the ventilation loss is reduced by 20% and 40%. In addition, when changing the diameter of the blade, the size of the windshield or fan cover should be changed accordingly. The dimensions that make them fit together are in accordance with the regulations. The gap between the fan blade and the fan cover should not be too large, generally between 1015. The air leakage loss from the high pressure region to the low pressure region is increased, and the original angle between the fan blade and the fan cover is maintained. A part of the moving pressure of the incoming air is converted into static pressure to reduce the loss. Of course, we can also use the fan rating to reduce the fan's air volume within the scope of the temperature rise permit. For example, the fan for the No. 8 base can be adjusted and trimmed to be used on the light-loaded motor of the No. 9 base. This will reduce the mechanical loss of the light-loaded motor of the No. 9 base and increase the temperature rise to improve the motor. Efficiency and power factor.
(2) Reduce friction to reduce mechanical loss
The normal operation of the motor bearing, noise, vibration, overheating, life and other factors are related to the reasonable choice of grease. At present, it is usually better to use No. 3 lithium base grease, which can reduce the mechanical loss, but with the rapid development of science and technology There are many greases with superior performance. For example, the performance of domestic small and medium-sized motor bearing greases has been tested by relevant departments to meet the standards of Japanese JIS222080 rolling bearing greases. It is close to the level of Swiss SKF65C grease, containing extremely low impurities, and the price is the same as No. 3 Lithium base grease is equivalent. There is also a good performance of the US Aesop grease currently on the market. We can use these good greases to improve the motor's operation to reduce mechanical losses. As a professional motor maintenance personnel, we can also work hard on the rational selection of bearings, but also energy saving; since we have a large number of motor losses, we can repair the motor. The bearings are used selectively. For example, on high-speed motors, we can use imported bearings or domestic high-grade B, C-class high-quality bearings to reduce the loss to the best. On low-speed motors, we can use domestically produced high-grade bearings C, D, In this way, we can save a sum of money on the bearings, so as to achieve the purpose of energy saving.
(3) Improve power factor to reduce mechanical loss
95% of the transfer equipment in the power plant is an AC asynchronous motor, and the AC asynchronous motor is a low power factor device. If you increase its power factor, you can make full use of the potential of power supply equipment, while reducing production costs and saving energy. Below, we discuss how to improve the power factor.
