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Motor energy saving is mainly achieved through six solutions such as selecting energy-saving motors, appropriately selecting motor capacity to achieve energy saving, using magnetic slot wedges instead of original slot wedges, using Y/△ automatic conversion devices, power factor reactive power compensation of motors, and liquid speed regulation of wound motors.
01 The energy consumption of the motor is mainly in the following aspects:
Motor load rate is low
Due to improper selection of the motor, excessive production or changes in the production process, the actual working load of the motor is far less than the rated load. About 30% to 40% of the installed capacity of the motor operates at 30% to 50% of the rated load. The efficiency is too low.
The power supply voltage is asymmetric or the voltage is too low.
Due to the imbalance of the single-phase load in the three-phase four-wire low-voltage power supply system, the three-phase voltage of the motor is asymmetrical, and the motor produces negative sequence torque, which increases the asymmetry of the three-phase voltage of the motor. The motor produces negative sequence torque, which increases Losses in the operation of large motors. In addition, the grid voltage has been low for a long time, which makes the current of the normally operating motor larger, thus increasing the loss. The greater the asymmetry of the three-phase voltage, and the lower the voltage, the greater the loss.
Old and obsolete motors are still in use
These motors use E-edge, are larger in size, have poor starting performance and low efficiency. Although it has been renovated over the years, there are still many places in use.
Poor maintenance management
Some units do not perform maintenance on motors and equipment as required and allow them to run for a long time, resulting in increasing losses. Therefore, it is worth studying which energy-saving solution to choose based on these energy consumption performances.
02 Six energy-saving solutions for motors
Choose energy-saving motors and high-efficiency motors to reduce various losses.
Compared with ordinary motors, the energy-saving motor is selected. The high-efficiency motor optimizes the overall design and uses high-quality copper windings and silicon steel sheets to reduce various losses. The loss is reduced by 20% to 30%, and the efficiency is increased by 2% to 7%; The investment payback period is generally 1 to 2 years, sometimes several months. In comparison, the efficiency of high-efficiency motors is 0.413% higher than that of J02 series motors. Therefore, it is imperative to replace old electric motors with high-efficiency electric motors.
Choose a motor with appropriate motor capacity
Appropriate selection of motor capacity to achieve energy saving has made the following provisions for the three operating areas of three-phase asynchronous motors: the load rate between 70% and 100% is the economic operation area; the load rate between 40% and 70% is the general operation area. ;Load rate below 40% is a non-economic operation zone. Improper selection of motor capacity will undoubtedly cause a waste of electrical energy. Therefore, using a suitable motor and improving the power factor and load factor can reduce power loss and save energy.
Use magnetic slot wedges to reduce no-load iron loss
The use of magnetic slot wedges instead of original slot wedges mainly reduces the no-load iron loss in asynchronous motors. The no-load additional iron loss is generated in the stator and rotor cores due to the harmonic flux caused by the cogging effect in the motor. of. The high-frequency additional iron loss induced by the stator and rotor in the iron core is called pulse vibration loss. In addition, the stator and rotor teeth are sometimes aligned and sometimes staggered, and the magnetic flux of the tooth clusters on the tooth surface changes, which can induce eddy currents in the tooth surface line layer and produce surface losses. Pulse vibration loss and surface loss are collectively called high-frequency additional losses, which account for 70% to 90% of the motor’s stray losses. The other 10% to 30% are called load additional losses, which are generated by leakage flux. Although the use of magnetic slot wedges will reduce the starting torque by 10% to 20%, the iron loss of the motor using magnetic slot wedges can be reduced by 60k compared with the motor using ordinary slot wedges, and it is very suitable for motor modifications for no-load or light-load starting.
Use Y/△ automatic conversion device to solve the problem of power waste
The Y/△ automatic conversion device is used to solve the waste of electric energy when the equipment is lightly loaded. The Y/△ automatic conversion device can be used to save energy without replacing the motor. Because in a three-phase AC power grid, different voltages obtained by different connections of the load are different, so the energy absorbed from the power grid is also different.
Motor power factor reactive power compensation reduces power loss
The main purpose of reactive power compensation for motor power factor is to improve the power factor and reduce power loss. Power factor is equal to the ratio of active power to apparent power. Generally, a low power factor will cause excessive current. For a given load, when the supply voltage is regular, the lower the power factor, the greater the current. Therefore, the power factor is as high as possible to save electric energy.
Liquid speed regulation of wound motors and liquid resistance speed regulation technology achieve no speed regulation.
Liquid speed regulation of wound motors and liquid resistance speed regulation technology are developed on the basis of the traditional product liquid resistance starter. The purpose of no speed regulation is still achieved by changing the plate spacing to adjust the size of the resistor. This makes it have good starting performance at the same time. It is powered on for a long time, which brings about the problem of heat generation and temperature rise. Due to the unique structure and reasonable heat exchange system, its working temperature is limited to a reasonable temperature. The liquid resistance speed regulation technology for wound motors has been rapidly promoted due to its advantages of reliable operation, convenient installation, large energy saving, easy maintenance and low investment. For those whose speed regulation accuracy is not high and the speed regulation range is not wide, and winding motors with infrequent speed adjustment, such as large and medium-sized winding asynchronous motors for fans, water pumps and other equipment, use liquid speed regulation to achieve significant effects.
