The principle of photocurrent transformer, the principle of current transformer

Photocurrent transformers, or MOCTs, are made according to the Faraday effect theory. It is based on the principle that there is a magneto-optical material (e.g. a piece of glass) that becomes optically active when exposed to a strong magnetic field.

Optical mobility means that when polarized light passes through a glass channel in a direction parallel to the applied magnetic field, the plane of light rotates or twists. Since Faraday first discovered this phenomenon, it has been observed in many solid, liquid, and gaseous substances. These substances are also called magneto-optical materials.

Photocurrent transformers have very significant advantages and economy, such as no saturation state, light weight, small size, high precision, no (EMI) geomagnetic influence, frequency bandwidth, good linearity, high insulation level, large dynamic measurement range, etc.

The principle of current transformer: it is based on the principle of electromagnetic induction.

A current transformer is made up of a closed core and windings. Its primary winding turns are very small, stringed in the line of the current that needs to be measured, so it often has all the current of the line flowing through, the number of secondary winding turns is more, connected in series in the measuring instrument and the protection loop, when the current transformer is working, its secondary circuit is always closed, so the impedance of the series coil of the measuring instrument and the protection loop is very small, and the working state of the current transformer is close to short circuit.

There is a huge disparity in the current in the lines of power generation, substation, transmission, distribution and consumption, ranging from a few amperes to tens of thousands of amperes. In order to facilitate measurement, protection and control, it needs to be converted into a relatively uniform current, and the voltage on the line is generally relatively high, so direct measurement is very dangerous. The current transformer plays the role of current conversion and electrical isolation.

Common faults of current transformers:

1. The insulation of the current transformer is very thick, some of the insulation is loosely wrapped around the reeds, there are wrinkles between the insulation layers, coupled with poor vacuum treatment, incomplete impregnation and resulting in air-containing cavities, which is easy to cause partial discharge faults.

2. The size and arrangement of the capacitive screen do not meet the design requirements of the matching posture, and even less discharge of the capacitive screen, and the capacitive plate is not smooth and flat, or even misaligned or broken, which destroys the voltage equalization characteristics. Therefore, when the electric field strength along the surface of the local solid insulation reaches a certain value, partial discharge will be caused. The direct consequence of the above-mentioned partial discharge is that the insulating oil is cracked, and a large amount of X-wax is generated between the insulating layers, and the dielectric loss increases.

This discharge has a cumulative effect, and if left unchecked, the gas in oil analysis will be characterized by arc discharge.

The above content refers to Encyclopedia - Current Transformer.

The working principle of the current transformer is made by using the characteristics of proportional primary and secondary currents of the transformer, so as to convert the large current into a small current through the proportion, which can be used for protection, measurement and other purposes.

The principle of a current transformer is to use the principle of electromagnetic induction to turn a high current into a low current. A current transformer consists of a main coil and a secondary coil. When the main coil is energized, a magnetic field is generated, and the secondary coil induces an electromotive force in the magnetic field, which produces an electric current.

The current of the secondary coil is directly proportional to the current of the main coil, but the current of the secondary coil is much smaller than that of the main coil, usually one hundredth or one thousandth.

Current transformers are used for protection, measurement, and other purposes. For example, a current transformer with a ratio of 400 5 can convert a current of 400A into a current of 5A. In addition, in order to ensure the safe and economical operation of the power system, the operation of the power equipment needs to be monitored and measured.

Applications of current inductors

Current transformers are widely used in power system macro-monitoring, mainly for measuring and protecting equipment. For example, in substations, current transformers can be used to measure current in order to monitor the operating status of the grid. In addition, current transformers can also be used to protect equipment, for example, in transformers, current transformers can be used to detect faults such as overload and short circuit, so as to cut off the power supply in time and protect the safe operation of equipment.

Current transformers also have a wide range of credit in industrial automation. For example, in a robot control system, a current transformer can be used to detect the current in the spine wheel of a motor in order to control the robot's movement. In addition, the current transformer can also be used to detect the load of the motor, so as to adjust the working state of the motor and improve production efficiency.

First, the role. The main function is to convert the large current in the AC circuit into a certain proportion of the small current (5** in China's standard) for measurement and relay protection. In the process of power generation, substation, transmission and distribution, due to the different electrical equipment, the current is often from tens of amperes to tens of thousands of amperes, and these circuits may also be accompanied by high voltage.

In order to be able to monitor and measure the circuits of these lines, and at the same time solve the dangers caused by high voltage and high current, current transformers are needed. Electrician's clamp meter, which is a device used to measure alternating current, its "clamp" is a through-center current transformer.

Second, the working principle.

The principle of the current transformer is based on the principle of electromagnetic induction, its primary winding often has all the current of the line flowing, when the current transformer is working, its secondary circuit is always closed, so the impedance of the series coil of the measuring instrument and the protection loop is very small, and the working state of the current transformer is close to short circuit.

In an ideal current transformer, the total magnetodynamic potential 0n0=0 is assumed if the no-load current is assumed, and according to the law of conservation of energy, the primary winding magnetokinetic potential is equal to the secondary winding magnetokinetic potential, i.e., 1ni=- 2n2

That is, the current of the current transformer is inversely proportional to its turns, and the ratio of the primary current to the secondary current 1 2 is called the current ratio of the current transformer. When the secondary current is known, the primary current can be found by multiplying the current ratio, and the phasor of the secondary current is 1800 different from the primary current.

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According to Qeeka Home experts, the role of the current transformer is simply to turn the high-voltage current into a secondary current after the transformation, which is used to protect and measure the role of the current, so what is the working principle of the current transformer? What is the working principle of the current transformerThe principle of the current transformer is based on the principle of electromagnetic induction, because the current generated in the process of power generation, power transformation and transmission is different, for example, some are only a few amperes and tens of thousands of amperes, in order to facilitate measurement and protection, so it needs to be converted into a unified current, so the current sensor can convert the current and isolate the electrical. For example, 1, for example, there is a very thick cable that needs car current, we must first disconnect the current first, and then connect the meter to this cable, but the current of this cable is very large, and our current meter is usually below 5A, so we need to use a current sensor to measure the current.

2. Select the appropriate current sensor, and pass the cable through the sensor to reduce the current in the cable to a certain multiple and then transmit it to the current test table, so that the measured value can be multiplied by the multiple to get the current amount. What should be paid attention to when using the current sensor1, the current ratio of the current sensor should be selected according to the rated current of the cable, for example, the transformer of 50 5 can only pass the current of 50A, and the transformer of 100 5 can only pass the current of 100A. 2. In the test table, the direct accuracy of the pointer from one-third to three-part and two-part of the combustion is relatively high, so it is best to choose a transformer with a range of one-third larger, such as a current of 50A, you can choose to use a transformer of 100 5.

3. There can be no open circuit in the process of using the transformer, that is, S1 and S2 on the transformer cannot be connected to the fuse. In order to prevent the generation of high-voltage currents, S1 and S2 must be connected to the ground. 4. According to the relevant national regulations, the square copper wire must be used for the high-voltage current on the transformer side.

To summarize the above is to introduce to you what is the working principle of the current transformer, I believe you will have a certain understanding of the current transformer, if you want to know more, you can pay attention to Qeeka Home.

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1. The principle of current transformer is based on the principle of electromagnetic induction. The transformer is composed of a closed crack core and a winding.

2. The main purpose of the current transformer is to convert the large current in the AC circuit into a certain proportion of the small current in China is 5 amperes, which is used for measurement and relay protection.

3. The principle of current transformer is based on the principle of electromagnetic induction. Its primary winding usually has all the currents flowing through the line.

4. When the current transformer is working, its secondary circuit is always closed, so the measuring instrument and the protection circuit are connected in series. The impedance is very small, and the working state of the current transformer is close to a short circuit.

A current transformer is a device used to convert current from a higher value to a current proportional to a lower value. It converts high-voltage current into low-voltage current, allowing large currents to flow through the transmission line and is safely monitored by an ammeter.

Current transformers are used with AC instruments, meters, or control devices where the current to be measured is so large that it is not convenient to give the meter or meter coil sufficient current-carrying capacity. The current transformer is shown in the figure below.

The core of the current transformer is composed of silicon steel laminations. For high precision, permalloy or mumetal is used to manufacture cores. The primary windings of the current transformer carry the current to be measured and are connected to the main circuit.

The secondary windings of the transformer carry a current proportional to the current being measured and are connected to the current winding of the meter or instrument.

The primary and secondary windings are insulated from the core and insulated from each other. The primary winding is a single-turn winding (also known as a rod primary) and carries a full-load current. The secondary windings of a transformer have a large number of turns.

The working principle of a current transformer is slightly different from that of a power transformer. In a current transformer, the impedance or secondary load of the load is slightly different from that of the power transformer. As a result, the current transformer operates under secondary circuit conditions.

Brand model: CHINT current transformer.

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A current transformer is used to convert a large current in an AC circuit into a certain proportion of a small current for measurement and relay protection. The current transformer is an instrument that converts the large current on the primary side into a small current on the secondary side according to the principle of electromagnetic induction. A current transformer is made up of a closed core and windings.

It has a small number of turns on the primary side winding and is strung in the line where the current needs to be measured.

According to different uses, current transformers can be roughly divided into two categories: current transformers for measurement (or measurement windings of current transformers): within the normal working current range, provide current information of the power grid to measurement, metering and other devices.

Protection current transformer (or protection winding of current transformer): In the case of power grid fault conditions, it provides grid fault current information to relay protection and other devices.

The maximum primary current of the transformer for protection can meet the requirements of the accuracy level under the rated load, which is called the rated accurate limit primary current. The accurate limit factor is the ratio of the rated accurate limit primary current to the rated primary current. When the primary current is large enough, the core will be saturated and will not reflect the primary current, and the accurate limit coefficient is an indication of this characteristic.