What is the Function of the Reactor? The Working Principle of the Reactor


What is a reactor

Usually, the resistance of capacitance and inductance to AC in the circuit can be called reactance, and the symbol is represented by X. What is a reactor? Some people in the industry also call it an inductor. When a conductor is energized, it will cause a magnetic field in a certain space it occupies. Therefore, all current-carrying electrical conductors will have a general sense. Induction performance.

However, in this case, the inductance of the energized long straight conductor will be relatively small, so the generated magnetic field will not be so strong, so the reactor, in practical application, uses a wire wrapped around a solenoid. In structural form, this type can be called an air-core reactor. At the same time, to make the solenoid have strong inductance performance, some special requirements will use the way of inserting the iron core into the tube to form a structure, and this type can be called an iron core reactor.

Generally speaking, reactance can be divided into capacitive reactance and inductive reactance. If we classify these terms from a professional perspective, then the inductive reactor (inductor) and capacitive reactor (capacitor) are collectively referred to as reactors.

The role of Reactors:

Because so many different reactors do different things, they can be split into two groups based on how their circuits work: in series and in parallel. Their main jobs are to limit the amount of current and filter it. Next, we’ll talk in-depth about how different reactors work. Here’s what you need to know:

Shunt Reactor:

It has many functions that can change and improve the reactive power-related operating conditions of the power system and is often used in reactive power compensation. In simple terms, the reactor can improve the voltage distribution on the long transmission line and absorb the charging capacitive reactive power in the cable line. The reactor can also effectively prevent the generator from self-excitation when the long line is connected. This resonance phenomenon.

Series Reactor:

Most of the time, it limits the current in a short circuit. It can also be linked to the filter’s capacitor in a series or parallel connection to limit the energy put into the power grid. High-order harmonics, or series reactors, limit the amount of current that can flow.

DC Reactor:

The frequency conversion system is usually put between the two units of the DC rectification link and the inverter link. The primary purpose is to limit the amount of AC current added to the DC current. It can effectively ensure that the rectified current stays the same and reduce the size of the current pulse. This means that the DC reactor can improve the power factor of the inverter and make the inverter link work more reliably and steadily.

Input Reactor:

Its primary purpose is to stop voltage spikes or sudden changes in the power grid. When the power supply voltage is smoothed, such as when spikes are removed, smooth bridge rectifier circuits are used. When the commutation causes voltage defects, the input reactor can effectively protect the inverter and improve the power factor. It can also stop interference from the power grid and reduce pollution of the power grid caused by the harmonic current generated by the rectifier unit.

Output Reactor:

It can be part of the capacitance between 50 and 200 meters, which is part of the compensation line. It can also block the harmonic output current to improve the high-frequency output impedance and block DV/DT to lower the high-frequency output impedance. Leakage protects the inverter and lowers the noise of the equipment. When the reactor is in the compensation power state, it is usually affected by harmonic voltage and current. This damages the capacitor and lowers the power factor. Because of this, the harmonics have to be controlled during compensation.

Current Limiting Reactor:

relatively speaking, it is much simpler and is mainly used in the power system. When a fault occurs, it will limit the overcurrent of the feeder (specifically, as shown in the figure below).

Current Limiting Reactor
Current Limiting Reactor

Smoothing Reactor:

It is an essential component of the rectifier circuit. When used in the intermediate frequency power supply, it is mainly used to limit the short-circuit current, that is to say when the inverter thyristor is performing commutation. When it is turned on, it is equivalent to a short-circuit fault directly in the rectifier bridge load, so no reactor is equivalent to a direct short-circuit, and it can suppress the impact of the intermediate frequency component on the power frequency grid.

The filtering effect is that when the rectified current has an AC component, the high-frequency AC is different and passes through a large inductance to make the rectified output waveform continuous or intermittent, and the current time will be zero. At this time, the inverter bridge Then stops working immediately and causes the rectifier bridge to open the circuit. The input power of the parallel inverter circuit has the throughput of reactive components, so the input circuit of the inverter bridge must have a reactor with the effect of energy storage.

Inverter Reactor:

This type of reactor is generally installed on the input or output terminal of the DC governor of the inverter, mainly to suppress the third to fifth harmonics generated by the inverter. The wave is transmitted to the power grid, and the interference of harmonics caused by frequency conversion to other components is reduced, the stability of the overall power grid is improved, and the power factor is improved. In addition, it can also limit the abnormal fluctuation of the power grid voltage and the impact on the power grid. Current, smooth the waveform and reduce the influence on the inverter.

In addition to the above, the inverter reactor also has the following essential functions: First, it can achieve the capacitive effect on the light no-load or light-load line, reducing the transient overvoltage phenomenon of the power frequency. Secondly, it can improve the voltage distribution on the transmission line and prevent the self-excitation resonance phenomenon with a certain probability of the generator with a long line. Finally, the reactor can make the reactive power in the line balance as much as possible at a light load, prevent the inappropriate flow of reactive power, and reduce the excessive power loss on the line.

Filter Reactor:

This reactor is often widely used in high and low-voltage filter cabinets. During installation, it will be connected with filter capacitors and tuned to a specific resonant frequency to absorb the power grid. The corresponding frequency harmonic currents appear in the system, and eliminating high-order harmonics harms the main transformer or other electrical equipment. The filter reactor mainly plays a vital role in absorbing power grid harmonics, improving the power factor of the system and terms of safety.

Tuning reactor:

AC power is passed through it. The function of the series reactor is to connect the capacitor in series to form a series resonance for the specified n-th harmonic component, to absorb the harmonic component, usually n=5, 7, 11, 13, 19.

Damping reactor:

Usually also called series reactor, connected in series with a capacitor bank or dense capacitor,

Used to limit the amount of current the capacitor draws when it closes. In this way, it does the same thing as a current-limiting reactor. When the filter reactor and the filter capacitor are connected in series, they make a resonant filter, usually used for resonance filtering of the 3rd to 17th order or higher-order high-pass filtering. Harmonic current sources include DC converter stations, phase-controlled static compensation devices, medium and large rectifier devices, electrified railways, and all power electronic circuits controlled by high-power thyristors. The harmonic current must be filtered out and kept from getting into the system. Harmonics in the power system are governed by specific rules set by the power industry.

Arc suppression coil:

Arc suppression coil is widely used in 10kV-63kV resonant grounding systems. Due to the oil-free tendency of substations, many arc suppression coils below 35kV are dry casting types.

The working principle of the reactor

In practical applications, the reactor is usually made of an air-core coil without magnetic conductive material, which can be arranged in three forms vertical, horizontal, and character direction positions according to the requirements. A relatively strong short-circuit current will be generated when a short-circuit fault occurs in the power grid system. If this situation is not restricted, it is challenging to ensure electrical equipment’s sustainable and stable operation. Therefore, to achieve the conditional requirements of a specific circuit breaker breaking capacity, the outgoing circuit breaker should permanently be installed. The reactor is connected in series to enhance the short-circuit impedance capability and limit the short-circuit current capability. The working principle of the reactor is shown in the figure below.

Because the reactor is chosen, when a short-circuit fault happens, its significant voltage drop can help keep the bus voltage level, which can incredibly well keep the bus voltage fluctuations within a small range to ensure no fault. The line’s equipment can work stably.

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