In the field, the interference of the frequency converter is more frequent and more serious, and even causes the control system to be unable to be put into use.
The operating principle of the inverter is destined to produce strong electromagnetic interference.
The inverter includes a rectifier circuit and an inverter circuit, and the input alternating current is converted into DC voltage through the rectifier circuit and flat-wave circuit, and then the DC voltage is converted into pulse voltage of different widths (called pulse width modulation voltage, PWM) through the inverter.
By using this PWM voltage to drive the motor, you can adjust the torque and speed of the motor. This principle of operation results in the following three types of electromagnetic interference:
1. Harmonic interference
The rectifier circuit will produce harmonic current, which produces a voltage drop on the impedance of the power supply system, resulting in the distortion of the voltage wavepattern, which interferes with many electronic devices (because most electronic devices can only work under the condition of sine wave voltage), and the common voltage distortion is the flattening of the top of the sine wave.
When the harmonic current is constant, the voltage distortion is more serious in the case of a weak power supply, and this interference is characterized by interference to equipment that uses the same power grid, regardless of the distance between the equipment and the inverter.
2. Radio frequency conduction emission interference
Because the load voltage is pulsed, the inverter draws current from the grid is also pulse, and this pulse current contains a large number of high-frequency components, forming radio frequency interference, which is characterized by interference to the equipment that uses the same power grid, regardless of the distance between the equipment and the inverter.
3. Radio frequency radiation interference
RF radiation interference comes from the input and output cables of the frequency converter.
In the above-mentioned RF conduction emission interference situation, when there is a radio frequency interference current on the input and output cables of the inverter, because the cable is equivalent to an antenna, electromagnetic wave radiation will inevitably be generated, resulting in radiation interference.
The PWM voltage transmitted on the output cable of the inverter also contains abundant high-frequency components, which will generate electromagnetic wave radiation and form radiated interference. Radiated interference is characterized by the phenomenon of interference becoming severe when other electronic devices are in close proximity to the frequency converter.
According to the basic principles of electromagnetism, there are three elements that must be present to form electromagnetic interference: the source of electromagnetic interference, the path of electromagnetic interference, and the system sensitive to electromagnetic interference.
In order to prevent interference, hardware anti-interference and software anti-interference can be used.
Among them, hardware anti-interference is the most basic and important anti-interference measures, generally from the anti-amplification and amplification two aspects to suppress interference, its general principle is to suppress and eliminate the source of interference, cut off the coupling channel of interference to the system, and reduce the sensitivity of the system interference signal.
Specific measures can be used in the project isolation, filtering, shielding, grounding and other methods.
The following are the main steps to resolve on-site interference:
1. Adopt software anti-interference measures
Specifically, the carrier frequency of the inverter is lowered through the human-machine interface of the inverter to an appropriate range.
If this method does not work, then the following hardware anti-interference measures can only be taken.
2. Carry out correct grounding
Through the specific investigation of the site, we can see that the grounding situation on the site is not ideal.
The correct grounding can not only effectively suppress external interference in the system, but also reduce the interference of the equipment itself to the outside world, which is an effective measure to solve the interference of frequency converters.
Specifically, it is to do the following:
(1) The main circuit terminal PE (E, G) of the inverter must be grounded, and the grounding can be shared with the motor of the inverter, but not with other equipment, and the grounding pile must be driven separately, and the grounding point should be as far away as possible from the grounding point of the weak current equipment.
At the same time, the cross-sectional area of the inverter grounding wire should not be less than 4mm2, and the length should be controlled within 20m.
(2) In the ground wire of other mechanical and electrical equipment, the protective grounding and the working grounding should be separately set up with a grounding electrode, and then merged into the electrical grounding point of the distribution cabinet.
The shielding ground of the control signal and the shielding ground of the main circuit wire should also be separately set up with a separate grounding electrode, and then integrated into the electrical grounding point of the distribution cabinet.
3. Shield the source of interference
Shielding the source of interference is a very effective way to suppress interference.
Usually the inverter itself is shielded with an iron shell, which can prevent its electromagnetic interference from leaking, but the output line of the inverter is better to be shielded with a steel pipe, especially when controlling the inverter with an external signal (output 4-20mA signal from the controller), the control signal line is required to be as short as possible (generally within 20m), and the shielded twisted pair must be used, and completely separated from the main power line (AC380) and the control line (AC220V).
In addition, shielded twisted pair cables are required for the circuits of the electronic sensitive equipment in the system, especially for pressure signals.
And all signal lines in the system must not be placed in the same piping or trunking as the main electrical line and control line.
For the shield to be effective, the shield must be reliably grounded.
4. Reasonable wiring
The specific methods are:
(1) The power line and signal line of the equipment should be as far away as possible from the input and output lines of the inverter.
(2) The power line and signal line of other equipment should be avoided parallel to the input and output lines of the inverter.
If the above methods do not work, then continue with the following methods:
5. Isolation of interference
The so-called interference isolation refers to isolating the interference source from the part that is susceptible to interference from the circuit, so that they do not have electrical contact.
Usually between the power supply and the amplifier circuit such as the controller and the transmitter, an isolation transformer is used on the power line to avoid conduction interference, and the power isolation transformer can be used to apply a noise isolation transformer.
6. Set the filter in the system line
The function of the device filter is to suppress the interference signal from the inverter through the power line to the power supply and the motor.
In order to reduce electromagnetic noise and loss, an output filter can be set on the output side of the inverter; In order to reduce interference with the power supply, an input filter can be set on the input side of the inverter.
If there are sensitive electronic devices such as controllers and transmitters in the line, a power noise filter can be installed on the power line of the equipment to avoid conduction interference.
Filters can be divided into the following categories according to the different locations where they are used:
(1) Input filter
There are usually two kinds:
a. Line filter: It is mainly composed of inductance coils, which weakens the harmonic current with higher frequency by increasing the impedance of the line at high frequency.
b. Radiation filter: It is mainly composed of high-frequency capacitors, which will absorb harmonic components with high frequency points and radiant energy.
(2) The output filter is also composed of an inductance coil
It can effectively weaken the higher harmonic component in the output current.
It not only plays an anti-interference role, but also weakens the additional torque caused by the harmonic current generated by the higher harmonics in the motor.
For the anti-interference measures at the output end of the inverter, the following aspects must be noted:
a. The output end of the inverter is not allowed to access the capacitor, so as not to generate a large peak charge (or discharge) current at the moment of power tube conduction (shutdown) and damage the power tube;
b. When the output filter is composed of LC circuits, the side of the capacitor connected to the filter must be connected to the motor side.
7. Adopt reactor
In the input current of the inverter, the harmonic components with lower frequencies (5th harmonic, 7th harmonic, 11th harmonic, 13th harmonic, etc.) account for a very high proportion, in addition to the normal operation of other equipment, but also because they consume a lot of reactive power, so that the power factor of the line is greatly reduced.
Serial insertion of reactors into the input circuit is an effective way to suppress lower harmonic currents.
Depending on the wiring position, there are two main types:
(1) AC reactor
It is connected in series between the power supply and the input side of the inverter.
Its main functions are:
a. Increase the power factor to (0.75-0.85) by suppressing the harmonic current;
b. Weaken the impact of the inrush current in the input circuit on the inverter;
c. Weaken the influence of power supply voltage imbalance.
(2) DC reactor
It is connected in series between the rectifier bridge and the filter capacitor.
Its function is relatively simple, that is, to weaken the higher harmonic components in the input current.
However, it is more effective than AC reactors in improving the power factor, up to 0.95, and has the advantages of simple structure and small size.
Therefore, the anti-interference measures of the inverter mainly include the installation of alternating current reactors and filters in the inlet part of the inverter, the incoming and outgoing wires adopt shielded cables, and the shielding layer of all cables is grounded together with the protective ground of the reactor, filter, inverter and motor, and the grounding point is separated from other grounding points and keeps sufficient distance.
At the same time, the signal cable and the power cable of the inverter should not be arranged in parallel.
In addition, in order to prevent the inverter from interfering with the signal and control loop, it is necessary to use a separate isolated power supply for the controller, instrument and industrial computer.
|
More on that
|
Analysis of common causes and preventive measures of inverter failures - Fuji Electric
1. Analysis of common faults in the main circuit
The main circuit is mainly composed of three-phase or single-phase rectifier bridges, smoothing capacitors, filter capacitors, IPM inverter bridges, current limiting resistors, contactors and other components. Many of these common faults* are caused by electrolytic capacitors. The life of an electrolytic capacitor is mainly determined by the ...
|
|
Fuji Electric - Precautions for inverter maintenance
In the summer, in terms of the inverter that is indispensable for equipment control and speed regulation, the scorching weather is the hard injury of the inverter's heating. A large number of existing studies and practices show that the failure rate of the inverter will increase with the increase of temperature, the service life will decrease with the increase of temperature, and the ambient temperature will rise.
|
|
Focusing on intelligent manufacturing, the Fuji Electric Technology Exchange Conference in South China has set off another boom
On June 26, the "2019 South China Fuji Electric System Products Intelligent Manufacturing Technology Exchange Conference" jointly sponsored by Fuji Electric (China) Co., Ltd., China Transmission Network and China Motion Control Industry Alliance was held in the boutique exhibition area of China Motion Control Industry Alliance at the South China Automation Exhibition (Shenzhen Convention and Exhibition).
|
|
The 10th China-Japan Energy Conservation and Environmental Protection Forum was held in Beijing, and Fuji Electric participated in the meeting and signed two cooperation projects.
On November 26, the 10th China-Japan Energy Conservation and Environmental Protection Comprehensive Forum, jointly sponsored by the National Development and Reform Commission, the Ministry of Commerce, the Ministry of Economy, Trade and Industry of Japan, and the Japan-China Economic Association, was held in Beijing. Xu Shaoshi, Director of the National Development and Reform Commission, Gao Yan, Vice Minister of Commerce, Minister of Economy, Trade and Industry of Japan ...
|
|
富士电机—变频器过压原因与措施
当我们在维修变频器的时候经常碰到触发了过压保护的变频器，在这个时候我经常想过，过压保护措施能否会因为过压的原因而导致不同吗？
（1）对于移相变压器的开断过电压，采用阻容吸收网络和氧 ...
|
|
变频器技术在注塑机中的应用
注塑成型是将热塑性塑料制成各种制品的主要成型方法之一，与其它塑料成型方法相比，注塑法具有可以成型结构复杂、尺寸***的制品，对塑料适应性强，成型周期短，生产效率高及易于实现自动化等优 ...
|
|
Current status and outlook of Fuji Electric's power generation plant business
Fuji Electric has set forth its management philosophy of "Contributing to a Rich Society, Challenging the Limits of Creativity, and Developing in Harmony with the Natural Environment," and one of the pillars of its management policy is to contribute to the sustainable development of society through energy and environmental businesses.
This article will focus on the energy sector ...
|
|
几种常用的污水处理检测仪表
大家平时都关注整个污水处理的大行业，而在污水处理中发挥很大作用的污水处理检测仪表，相信一定很少关注，今天小编整理了几种常用的污水处理检测仪表，希望对大家有帮助。
一、超声波液位计
...
|
|
Fujifilm inverter – the difference between inverter and soft starter
Frequency converters and soft starters are actually two completely different products. The inverter is mainly used in the place where the motor regulates the speed, and the inverter has the performance of soft starter and other starters, and at the same time, it also has great advantages over other starter devices in terms of starting characteristics. At the start of the current ...
|
|
Five common errors in instrumentation measurements
1. Method errors
It refers to the error caused by the imperfection of the measurement method used, the imprecise theoretical basis, and the inappropriate modification and simplification of some classical measurement methods, that is, all the factors that are not reflected in the expression of the measurement results, but in fact these factors play a role...
|
|
Fuji Electric's Power Semiconductor Symposium officially kicked off
On March 16, 19, Fuji Electric Power Semiconductor Symposium was held in Guangzhou. More than 90 customers and agents from all over the country were invited. Fuji Electric looks forward to carrying out in-depth communication with you according to the publicity and education content of this seminar, so that everyone can have a good understanding of Fuji Electric.
|
|
常见传感器有哪些，是如何工作的？
什么叫传感器
微型化、数字化、智能化、多功能化、系统化、网络化。它是实现自动检测和自动控制的首要环节。传感器的存在和发展，让物体有了触觉、味觉和嗅觉等感官，让物体慢慢变得活了起来。 ...
|
|
Can ultrasonic flowmeters be used in the production and processing of edible oil?
Can a small flow ultrasonic flow meter be used for flow measurement of soybean oil?
There are several steps in the processing of edible oil that require the use of flow meters to measure the volume and weight of how much oil flows out of the pipeline. Enterprises that produce and process edible oil need to be aware of the crude oil and ...
|
|
城市自来水公司，"供求"矛盾，如何解决 富士便携式流量计应用
城市管网流量的测定是供水企业在管网管理中的一项重要工作。几年来，我公司使用日本富士便携式超声波流量计，为用水大户测定用水量，以科学的数据说服并缓解了这些企业与公司的"供求"矛盾;尤其 ...
|
|
Fuji Electric joined hands with students from Zhejiang University to carry out environmental protection activities on road surfaces in Hangzhou
Fuji Electric's CSR can be seen as the implementation of the "Management Philosophy" and "Management Policy", which means that through energy and environmental business, we contribute to the resolution of social issues, maximize the positive impact of corporate activities on society and the environment as a whole, and prevent or reduce negative impacts.
|
|
The inverters we "installed" together in those years
1. First confirm the installation environment of the inverter
I. Operating temperature. The inverter is a high-power electronic component, which is very susceptible to the influence of working temperature, and the product is generally required to be 0-55 °C, but in order to ensure the safety and reliability of the work, it should be considered to leave room for use, and it is good to control it at 4 ...
|
|
Fuji Electric will increase its production capacity of next-generation power semiconductors by 10 times by 2024
On July 26, it was reported that Fuji Electric will increase the production capacity of a new generation of power semiconductors in 2024 to about 10 times that of 2020.
Recently, it was reported that in order to cope with the growing demand for silicon carbide power semiconductors in the fields of pure electric vehicles (EVs), Fuji Electric plans to launch a new ...
|
|
手持式超声波流量计的使用方法
手持式超声波流量计是流量检测必备的工具仪表。它是为了提高测量流量的方便性而设计的，具有测量精度高、量程比大、无压损、无可动部件，并且体积小，重量轻，只需要将传感器安装在管道外壁上即 ...
|
|
富士变频器——第7代“X系列”产业用1200V/2400A RC-IGBT模块
为满足IGBT模块小型化和高可靠性化的市场要求，富士电机开发了将IGBT和FWD单芯片化的RC-IGBT（Reverse-Conducting IGBT）。
将第7代“X系列”芯片技术及封装技术与RC-IGBT技术相结合，使第7代 ...
|
|
【In-depth Interpretation】Cybersecurity of Safety Instrumented System (SIS).
When a company begins a Safety Instrumented System (SIS) project, the first decision stakeholders must make is to choose the system architecture. By complying with international cybersecurity standards such as IEC 62443 (ANSI/ISA 62443 series of standards) as well as international process industry automation users...
|
|
Contact
working hours
