What is a reactor?
A reactor, also called an inductor, is an electrical device that generates a magnetic field within a certain space when current flows through it. Therefore, all current-carrying conductors possess inductance in a general sense. However, the inductance of a long, straight current-carrying conductor is relatively small, and the magnetic field it produces is not strong. Therefore, practical reactors are made by winding wire into a solenoid, called air-core reactors. Sometimes, to give this solenoid a larger inductance, an iron core is inserted inside, called an iron-core reactor. Reactance is divided into inductive reactance and capacitive reactance. A more scientific classification is that inductors and capacitors are collectively called reactors. However, because inductors were developed first and were called reactors, the term "capacitor" now refers to a capacitive reactance, while "reactor" specifically refers to an inductor.
Does a 132kW motor controlled by a frequency converter need to have incoming and outgoing line reactors added?
Adding an incoming line reactor can suppress the interference of the frequency converter to the power grid, while adding an outgoing line reactor can suppress harmonics and reduce losses. Adding one is better, but it's not necessary.
A 132kW inverter is a high-power device, and its operation can cause some interference to nearby electronic equipment and power supplies. Adding an inverter is certainly good, but not essential. If the inverter uses a single power supply and there are other lower-power devices or electronic equipment in the working environment, it's recommended to add an inverter. Otherwise, sometimes inexplicable problems may occur, and the cause may be difficult to pinpoint!
For a 110KW fan with variable frequency control, should a reactor be added to the inverter? Should it be added to the input terminal or the motor terminal? The cable from the inverter to the motor is 120 meters long.
No, it's not necessary. The input reactor is added to prevent interference from the input power supply, and the output reactor is used to reduce the interference of the inverter's input pulse wave to the outside world and to attenuate high-frequency pulses. In general, neither is required.
A 110kW fan typically uses 150 square millimeter cable, which is more than sufficient for a distance of 120 meters without any voltage drop issue. Therefore, there's no need to add a reactor. Furthermore, even if an output reactor were to be added, it would need to be specifically designed for the corresponding frequency converter, which is very expensive.
The output reactor core temperature reaches 130 degrees Celsius. What can be done to solve this? The cable from the frequency converter to the motor is 500 meters long.
The harmonic content is too high, resulting in excessive eddy current losses in the iron core.
1) If remanufacturing is required, the excitation loss can be reduced by replacing the silicon steel sheet with a low-loss one; or a thinner silicon steel sheet can be selected to reduce eddy current losses; or the designed magnetic flux density Bm can be reduced.
2) If it is already a finished product, you can add a fan to cool it down; or increase the inductance in the circuit, which can reduce the harmonic content and reduce the eddy current loss of the iron core.
The motor is 150kW and needs to be started with a frequency converter. Should a reactor or a contactor be added to the input of the frequency converter? What are the advantages of each?
You can simply install an automatic air circuit breaker. Adding a reactor can slow down the attenuation of the input voltage. You cannot install a contactor; it's pointless.
How long of the cable connecting the frequency converter and the motor requires the installation of a reactor?
When the distance between the frequency converter and the motor is long, the voltage drop of the cable will reduce the motor torque and increase the high-frequency leakage current of the cable, thereby increasing the output current of the frequency converter and causing it to trip due to overcurrent. Measures should be taken to reduce distributed capacitance (avoid using metal conduits on the cable and connect each phase cable separately, etc.), and the carrier frequency should be reduced to decrease the high-frequency leakage current.
How long of a cable do you need to install a reactor? The length of the cable is irrelevant when it comes to installing a reactor.
Installing reactors can help improve the power factor on the power supply side.
A DC reactor or AC reactor must be installed in the following situations:
1. When the frequency converter is connected to a power transformer of 600KVA or above or when switching the phase-advancing capacitor.
2. When a DC driver or other thyristor converter is connected to the same power supply system, a DC reactor or AC reactor must be installed.
How to select a suitable frequency converter based on the motor power? Under what circumstances can reactors not be added to the input and output terminals of a frequency converter?
When selecting a frequency converter, the corresponding manufacturer provides a power matching table, which is a more reasonable approach. Alternatively, you can contact their technical support by phone.
Generally, you can choose based on the power. The power of the frequency converter should be the same as the power of the motor. Usually, you don't need to add a reactor. A large frequency converter can drive a small motor without any problem, but a small frequency converter cannot drive a large motor. The reason is simple: it's easy for you to carry your child, but it's difficult for your child to carry you.
What happens if the motor has a low power rating but the selected frequency converter has a high power rating? No problem.
What happens if a high-power motor is driven by a low-power inverter? The motor won't be able to drive it, and the inverter will report an overcurrent error.
If the motor has low power while the frequency converter has high power, it's like using a large horse to pull a small cart. In this situation, the frequency converter's protection functions may fail, such as overcurrent and overload protection. Furthermore, it increases investment costs.
A high-power motor with a low-efficiency inverter is like a small horse pulling a large cart. The small horse gets exhausted, but the cart may not be able to move. Even if it does, the small horse will age prematurely due to overwork.
If the inverter is too small, the start-up will not be smooth, and it may even be difficult or burn out the inverter. This is certain. Generally, an input line reactor is added to the input end of the inverter when the power grid is unstable. If the power grid is stable, the input line reactor does not need to be added. The selection of the output side reactor generally depends on the distance between the inverter and the motor. If it is not too far, it can be omitted. If it exceeds 100 meters, it must be added!
Why do frequency converter cabinets need to have incoming line reactors, outgoing line reactors, and DC reactors?
Input line reactors are used for interference suppression to prevent mutual interference between the frequency converter and other equipment. Output line reactors are used for filtering. The carrier frequency of a typical frequency converter is between 2 and 10 kHz; filtering with these reactors can make the output waveform smoother. Input line reactors prevent harmonic interference caused by the frequency converter to the power grid and surrounding equipment. Reactors are used to optimize the AC waveform output by the frequency converter, as the frequency converter outputs a high-frequency rectangular wave. They also prevent ground capacitance on the output side of the frequency converter and extend the cable length from the frequency converter to the motor side.
Is it better to add a filter or an input line reactor before the frequency converter?
reactor
The reactors used in power grids are essentially hollow coils without magnetic materials. They can be arranged in three configurations: vertical, horizontal, and triangular. When a short circuit occurs in a power system, a very large short-circuit current is generated. Maintaining the dynamic and thermal stability of electrical equipment without limiting it is extremely difficult. Therefore, to meet the breaking capacity requirements of certain circuit breakers, reactors are often connected in series at the outgoing circuit breakers to increase the short-circuit impedance and limit the short-circuit current. Because of the reactors, the voltage drop across them is significant during a short circuit, thus also helping to maintain the bus voltage level, minimizing voltage fluctuations on the bus and ensuring the stability of user electrical equipment on non-faulty lines.
filter
A filter is a circuit that effectively filters out frequencies at a specific frequency or frequencies outside that frequency. Its function is to obtain a specific frequency or eliminate a specific frequency.
This property can be used to obtain a sine wave of a specific frequency from a square wave group or a complex noise wave passing through a filter.
Incoming line reactor
The primary purpose of the incoming line reactor is to reduce harmonic currents in the rectifier and rectifier/feedback units of the frequency converter, while also reducing commutation gaps. The reactor's function is related to the ratio of grid short-circuit power to drive power. A ratio of grid short-circuit power to drive power of >33:1 is recommended.
Incoming line reactors can also limit current surges caused by sudden drops in power supply potential (such as due to compensation equipment or grounding faults).
What factors need to be considered when selecting an incoming line reactor?
1) The current of the input reactor can be selected according to the input current of the device, that is, the operating current of the input reactor should be selected according to the maximum input current of the frequency converter; 2) Input reactor voltage drop value:
When the rectifier unit of the frequency converter is a non-feedback rectifier, the input reactor should be selected with a voltage drop of 2%.
When the rectifier unit of the frequency converter is a feedback rectifier, a 4% grid-side incoming line reactor should be used.
Applications requiring the installation of incoming line reactors
The incoming line reactor can prevent interference from the power grid and reduce the pollution of the power grid by harmonic currents generated by the rectifier unit. When the power supply capacity is large, it is even more important to prevent current surges caused by various overvoltages, as these are harmful to the rectifier diodes and filter capacitors inside the frequency converter. Therefore, connecting an incoming line reactor is beneficial to improving the operating condition of the frequency converter. According to operating experience, an incoming line reactor must be installed in the following situations to ensure the reliable operation of the frequency converter: 1) The power supply capacity is 600kVA or above, and the frequency converter is installed within 10m of the large-capacity power supply;
2) The three-phase power supply voltage imbalance rate is greater than 3%; 3) Other thyristor converters share the same input power supply with the frequency converter, or the input power supply terminal is connected to a capacitor device that can be switched by a switch to adjust the power factor.
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