The role of inverter in electric motor control

Through the inverter drive motor has become an irreversible trend, today I will talk about the role of the inverter in motor control

For electric motor , when produced in strict accordance with the design parameters and process parameters, the variability of the rotational speed of electric motors with the same specifications is very small, generally not more than two revolutions.

For electric motors of single-dragging equipment, there is no overly demanding requirement on electric motor speed, but for multiple motors dragging equipment or equipment systems, the control of electric motor speed is very important.

In the traditional transmission system, to ensure a certain relationship between the speed of multiple actuators, which includes ensuring that the speed between them is synchronized or has a certain speed ratio, often using mechanical transmission rigid coupling device to achieve.

However, if the mechanical drive between multiple actuators is large, the distance between the actuators is far, you have to consider the use of independent control of non-rigid coupling drive control method.

With the maturity of the inverter technology and the expansion of the use of the scope, the programmable controller can be used to control it, so as to adapt to the different requirements of speed control flexibility, accuracy and reliability in the transmission system.

Examples of actual production application of PLC and inverter for speed control can also better achieve the expected synchronous or given speed ratio control requirements.

The role and function of the inverters

Inverter energy-saving role;

The energy-saving effect of inverters is mainly shown in the application of fans and pumps.

After the fan and pump loads adopt frequency conversion speed control, the energy saving rate is 20% to 60%, which is because the actual power consumption of fan and pump loads is basically proportional to the third power of the rotational speed.

When the average flow required by the user is small, fans and pumps use variable frequency speed regulation to reduce their speed, the energy-saving effect is very obvious.

The traditional fans and pumps use baffles and valves to adjust the flow rate, the motor speed is basically unchanged, and the power consumption does not change much.

According to statistics, fans and pumps account for 31% of the national electricity consumption, accounting for 50% of industrial electricity consumption.

The use of variable frequency speed control devices on such loads is of great importance. At present, the more successful applications are constant pressure water supply, all kinds of fans, central air conditioning, and hydraulic pump frequency conversion speed regulation

inverter to realize soft start of motor

Direct starting of electric motor will not only cause serious impact to the power grid, but also will require too much power grid capacity, and the high current and vibration generated during starting will cause great damage to the baffle and valve, which is extremely unfavorable to the service life of the equipment and pipeline.

And after using the inverter, the soft start function of the inverter will make the starting current change from zero, and the maximum value will not exceed the rated current, which reduces the impact on the grid and the requirement of power supply capacity, prolongs the service life of the equipment and valves, and also saves the maintenance cost of the equipment.

Application of inverter in automation system

Because the inverter has a built-in 32-bit or 16-bit microprocessor, with a variety of arithmetic logic operations and intelligent control functions, output frequency accuracy of 0.1% ~ 0.01%, and set up a perfect detection, protection links, therefore, in the automation system is widely used.

For example: winding, stretching, metering and guiding in the chemical fiber industry; flat glass annealing furnace, glass kiln stirring, edge pulling machine and bottle making machine in the glass industry; automatic charging and dosing system of electric arc furnace and intelligent control of elevator, etc.

The application of frequency converter in the control of CNC machine tools, automotive production lines, paper and elevators to improve the level of process and product quality.

Application of inverter in improving process level and product quality

Inverters can also be widely used in various mechanical equipment control fields such as transmission, lifting, extrusion and machine tools, etc. It can improve the process level and product quality, reduce the impact and noise of the equipment, and extend the service life of the equipment.

The use of frequency conversion speed control simplifies the mechanical system, makes operation and control more convenient, and in some cases can even change the original process specifications, thus improving the function of the entire equipment.

For example, the temperature inside the machine of the sizing machine used in textile and many industries is regulated by changing the amount of hot air fed into the machine.

The hot air is usually delivered with a circulating fan, and since the fan speed remains unchanged, the amount of hot air fed into the machine can only be adjusted with a damper.

If the dampers fail to adjust or improperly adjust, it will cause the shaping machine to lose control, thus affecting the quality of the finished product.

The circulating fan starts at high speed, and the wear between the drive belt and the bearing is very strong, making the drive belt a consumable product.

After adopting frequency control, temperature adjustment can be achieved by automatically adjusting the speed of the fan through the frequency converter, which solves the problem of product quality. In addition, the frequency converter can easily realize the fan in low frequency and low speed start and reduce the wear and tear between the drive belt and the bearing, but also can extend the service life of the equipment, while saving energy by 40%.

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Dongchun motor is a professional manufacturer of electric motors for more than 15 years experience in China.