Capacitors play multiple roles in circuits, with various types and unique characteristics for each. From the perspective of circuit principles, reactors can be roughly divided into two categories: series and parallel. The main functions of these two types of reactors are current limiting and filtering, respectively. Next, we will delve into the specific functions of various types of reactors.
1. The main function of parallel reactors is to optimize the reactive power operation of power systems and is often used for reactive power compensation. It can effectively improve the distribution of voltage on long-distance transmission lines, absorb charging capacitive reactive power in cable lines, and prevent self excitation resonance of generators with long lines.
2. Series reactors are mainly used to limit short-circuit currents. In addition, it can also be connected in series or parallel with capacitors in filters to limit high-order harmonics in the power grid. Overall, series reactors play a role in limiting current.
3. DC reactors are often placed between the DC rectifier and inverter links in frequency conversion systems. Its function is to limit the AC component superimposed on the DC current, ensure the continuity of the rectified current, and reduce the current pulse value. This helps to improve the stability of the inverter link and improve the power factor of the frequency converter.
4. The main function of the input reactor is to protect the frequency converter, improve power factor, and prevent grid interference. It can also effectively reduce the pollution of the power grid caused by the harmonic current generated by the rectifier unit. When there is a sudden voltage change or overvoltage operation in the power grid, the input reactor can limit the current surge and protect equipment safety.
5. The function of the output reactor is to compensate for the influence of line capacitance, usually within the range of 50 meters to 200 meters. It can not only suppress output harmonic currents, but also improve output high-frequency impedance, reduce DV/DT, and minimize high-frequency leakage phenomena, thereby protecting the frequency converter and reducing equipment noise. In the compensating power state, the reactor may be impacted by harmonic voltage and current, so it is necessary to control the harmonics to ensure the stability of the capacitor and power factor.
6. Current limiting reactors are mainly used for fault limitation in power systems. When a fault occurs, it can effectively limit the overcurrent of the feeder and ensure the safe and stable operation of the system.
7. Flat wave reactors play a crucial role in rectifier circuits. It is mainly used for intermediate frequency power supply, aiming to limit short-circuit current. When the inverter thyristor performs commutation operation, if a short circuit fault occurs in the rectifier bridge load, the reactor can effectively prevent direct short circuit and ensure system safety. In addition, it can also suppress the adverse effects of intermediate frequency components on the power grid.
In rectified current, the AC component may cause high-frequency AC to interact with large inductance, resulting in a continuous or intermittent waveform of the rectified output, leading to the moment when the current time is zero. At this point, the inverter bridge will immediately stop working, which may cause the rectifier bridge to open circuit. Therefore, the input power of a parallel inverter circuit contains reactive power components. In order to ensure the normal operation of the inverter bridge, a reactor with energy storage function must be equipped in the input circuit.
Reactors play a crucial role in rectifier circuits. Its working principle is mainly based on electromagnetic induction, which introduces inductance into the circuit to hinder the change of current, thus achieving the regulation of the circuit. Reactors can limit short-circuit current, protect the system from direct short-circuit damage, and ensure the safe and stable operation of rectifier circuits. At the same time, it can effectively suppress the adverse effects of intermediate frequency components on the power grid and improve the overall performance of the system. In rectified current, the presence of AC components may cause high-frequency AC to interact with large inductance, resulting in the moment when the current time is zero. In order to avoid this situation from affecting the inverter bridge and causing the rectifier bridge to open circuit, a reactor with energy storage function must be equipped in the input circuit to ensure the normal operation of the inverter bridge.
8. The function of the inverter reactor: This type of reactor is often installed on the input or output terminals of the DC speed controller of the inverter, aiming to suppress the transmission of the third to fifth harmonics generated by the inverter to the power grid, thereby reducing the interference of harmonics on other components. At the same time, it can optimize the overall stability of the power grid, improve power factor, and limit abnormal fluctuations in grid voltage. In addition, the reactor can effectively cope with the surge current on the power grid, smooth out the waveform, and thereby reduce the impact on the frequency converter.
In addition, the inverter reactor also has multiple other functions. Firstly, it can alleviate the capacitance effect on no-load or lightly loaded lines and reduce the risk of transient overvoltage at power frequency. Secondly, by improving the voltage distribution on the transmission line, this reactor helps prevent self excitation magnetic resonance that may occur when the generator is carrying a long line. Thirdly, under light load conditions, the reactor can promote the local balance of reactive power in the line as much as possible, prevent improper flow of reactive power, and thus reduce power loss on the line.
9. The function of filter reactor: This reactor plays an important role in high and low voltage filter cabinets and is often used in series with filter capacitors. It can tune to a specific resonant frequency, effectively absorbing the corresponding frequency harmonic currents in the power grid and reducing the damage of high-order harmonics to the main transformer and other electrical equipment in the system. In addition, the filter reactor is also responsible for improving the system power factor, which is of great significance for the safe and stable operation of the power grid.
