In industrial control, we often need to use a frequency converter to convert the industrial frequency power supply into various frequencies of the AC power supply, in order to realize the variable speed operation of the motor. With the increasing degree of industrial automation, frequency converters are also widely used. Therefore, how to choose the right frequency converter for the motor is a common concern.
Frequency converter is the application of frequency conversion technology and microelectronics technology, by changing the motor operating power frequency mode, so as to control the AC motor power control equipment. It can save energy, regulate the speed of the motor, and provide safety protection.
01
According to the working current selection inverter
Motor operating current is a key factor in the selection of frequency converter, frequency converter must meet the output current is greater than the actual operating current of the motor when working for a long time. Therefore, the operating current characteristic curve needs to be used as a reference basis.
Specifically, the selection should be matched in terms of voltage, current and torque. So in order to ensure that the inverter can work properly, we are required to have a comprehensive and thorough understanding of the site's power situation, which includes the level of the power supply voltage, the quality of the voltage waveform and so on.
At the same time, we also need to have a certain knowledge of the load: the performance curve of the load determines the application method of the frequency converter, ordinary centrifugal pump frequency converter rated current, and the rated current of the motor in line with the deep water pump requires a larger current.
02
According to the use of environmental selection of frequency converter
Frequency converter selection, should also fully consider the impact of the environment on the frequency converter:
If the site of the motor needs frequent starting and braking, it is necessary to install braking resistance, braking resistance size should be selected based on the size of the power;
If the environment of the factory is harsh, dusty and difficult to dissipate heat, water-cooled inverter should be selected, which can effectively prevent the module from blowing up and effectively reduce the noise;
If it is necessary to do aging test equipment, you can consider using four-quadrant products, effectively reducing power loss;
If the work site has a separate DC power, you can only use pure inverter modules, saving economic investment.
In short, according to the local conditions, according to different site conditions to choose different inverter, is a constant guideline.
03
Selection of inverter according to control purpose
In addition, general industrial motors are AC induction motors, which can use constant voltage control or constant current control, and according to the different control purposes of the motor, the frequency converter can be selected is not the same.
For example, need to drive high-speed motors, due to the small reactance of high-speed motors, high harmonics increase resulting in increased output current value, so you need to use the capacity to be slightly larger than the ordinary motor frequency converter.
The need to use long cable operation, it is necessary to take measures to inhibit the influence of long cable coupling capacitance on the ground, the frequency converter capacity to be enlarged by one grade, or in the output side of the frequency converter to install the output reactor, to avoid insufficient output of the frequency converter.
Frequency converter selection depends on many factors, should be based on the operating current, the use of the environment, the control of the purpose of the three aspects of the requirements in order to choose the right frequency converter in industrial control, in the production process and production economy to balance between.