The hottest way to improve motor energy efficiency

2022-08-12
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Improve motor energy efficiency and promote system energy conservation

the electric energy consumed by motors accounts for about 60% - 70% of the total power generation. The efficiency of more than 80% of motor products in China is 10% lower than the foreign advanced level on average. The energy conservation of Motors has been listed as one of the top ten national energy conservation projects by relevant national departments, and its goal is to increase the efficiency of small and medium-sized motors from 87% to 90% - 92% by 2010. In order to achieve this goal, it is particularly urgent to improve motor energy efficiency and promote system energy conservation

motor energy consumption performance

motor energy consumption performance is mainly in the following aspects: first, the motor load rate is low. Due to improper motor selection, excessive margin or changes in production process, the actual working load of the motor is far less than the rated load. The motor accounting for about 30% - 40% of the installed capacity operates at 30% - 50% of the rated load, and the operating efficiency is too low

second, the power supply voltage is asymmetric or too low. Due to the imbalance of single-phase load in the three-phase four wire low-voltage power supply system, the three-phase voltage of the motor is asymmetric, and the motor produces negative sequence torque. Increasing the three-phase voltage asymmetry of the motor, the motor produces negative sequence torque, and increases the loss in the operation of the motor. In addition, the electric voltage is low for a long time, which makes the current of the motor in normal operation larger, so the loss increases. The greater the asymmetry of three-phase voltage, the lower the voltage, the greater the loss

third, the old and old (obsolete) motors are still in use. These motors adopt E-class insulation, with large volume, poor starting performance and low efficiency. Although it has undergone years of transformation, it is still used in many places

fourth, poor maintenance management. Some units did not repair and maintain the motors and equipment as required, allowing them to operate for a long time, resulting in increasing losses

therefore, in view of these energy consumption performance, it is worth studying which energy-saving scheme to choose

seven energy-saving schemes for motors

there are roughly seven energy-saving schemes for motors at present. Experts analyzed one by one that energy-saving motors should be selected. Compared with ordinary motors, the overall design of high-efficiency motors is optimized, and high-quality copper windings and silicon steel sheets are selected, which reduces various losses, reduces losses by 20% - 30%, and improves efficiency by 2% - 7%; The payback period of investment is generally 1-2 years, sometimes several months. In comparison, the efficiency of high-efficiency motor is 0.413% higher than that of J02 series motor. Therefore, it is imperative to replace the old motor with high-efficiency motor

properly select the motor capacity to save energy. The state has made the following provisions for the three operation areas of three-phase asynchronous motors: the economic operation area is the load rate between 70% and 100%; The load rate between 40% and 70% is the general operation area; Load rate below 40% is non economic operation area. Improper selection of motor capacity will undoubtedly cause a waste of electric energy. Therefore, using appropriate motor and improving power factor and load rate can reduce power loss and save electric energy

replace the original slot wedge with magnetic slot wedge. The magnetic slot wedge mainly reduces the no-load iron loss in the asynchronous motor. The no-load additional iron loss is generated in the stator and rotor core by the harmonic magnetic flux caused by the cogging effect in the motor. He Qing, director of the Liaoning Provincial Department of industry and information technology, said that the high-frequency additional iron loss induced in the core is called pulsation loss. In addition, the stator and rotor teeth are sometimes aligned and sometimes staggered, and the magnetic flux of the tooth cluster on the tooth surface changes, which can induce eddy current in the tooth surface line layer and produce surface loss. Pulse loss and surface loss are collectively called high-frequency additional loss, which account for 70% - 90% of the stray loss of the motor, and the other 10% - 30% is called load additional loss, which is generated by magnetic flux leakage. Although the use of magnetic slot wedge will reduce the starting torque by 10% - 20%, the iron loss of the motor with magnetic slot wedge can be reduced by 60K compared with the motor with ordinary slot wedge, and it is very suitable for the transformation of the motor with no-load or light load starting

adopt Y/△ automatic conversion device. In order to solve the waste of electric energy when the equipment is under light load, Y/△ automatic conversion device can be used to save electricity without replacing the motor. Because in three-phase alternating current, the voltage obtained by different connection methods of load is different, so the energy absorbed from electricity is also different

reactive power compensation of motor power factor. The main purpose of reactive power compensation is to improve power factor and reduce power loss. Power factor is equal to the ratio of active power to apparent power. Generally, low power factor will cause excessive current. For a given load, when the power supply voltage is constant, whether it can go out and invest, the lower the power factor, the greater the current. Therefore, the power factor should be as high as possible to save electric energy

variable frequency speed regulation. Most fan and pump loads are selected according to the demand of full load operation, and most of the time in practical application is not in full load operation. Because it is difficult to adjust the speed of AC motor, the common wind deflector can adjust the air volume or flow when the cleaning, lubrication and other conditions are met, the return valve or the startup and shutdown time. At the same time, it is difficult for large motors to start and stop frequently under the power frequency state, and the power impact is large, which is bound to cause power loss and current impact during startup and shutdown. Using frequency converter to directly control the load of fans and pumps is the most scientific control method. When the motor operates at 80% of the rated speed, the energy-saving efficiency is close to 40%. At the same time, it can also realize closed-loop constant pressure control, and the energy-saving efficiency will be further improved. Because the frequency converter can realize the soft stop and soft start of large motors, it avoids the voltage shock during startup, reduces the motor failure rate, prolongs the service life, and reduces the electrical capacity requirements and reactive power loss

liquid speed regulation of wound motor. The Northeast falling speed regulation technology of liquid resistance is developed on the basis of the traditional product liquid resistance starter. The purpose of stepless speed regulation is still achieved by changing the distance between the plates to adjust the resistance. This makes it have good starting performance at the same time. It is powered on for a long time, which brings the problem of heating up. Due to the unique structure and reasonable heat exchange system, its working temperature is limited to a reasonable temperature. Liquid resistance speed regulation technology for wound motor has been rapidly promoted for its advantages of reliable operation, convenient installation, large energy saving range, easy maintenance and low investment. For some wound motors with low speed regulation accuracy and wide speed regulation range, and infrequent speed regulation, such as large and medium-sized wound asynchronous motors of fans, pumps and other equipment, the effect of liquid speed regulation is remarkable

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