The principle of the transformer Classification Functional use?

Transformer includes voltage transformer and current transformer.

Voltage transformer is a kind of voltage conversion device, which has the dual functions of voltage conversion and isolation, which converts the high voltage of the high-voltage circuit or low-voltage circuit into low voltage (generally 100V), and supplies the instrument and relay protection device to achieve measurement, measurement, protection and other functions.

The current transformer is a kind of current conversion device, which has the dual functions of current conversion and isolation, which converts the large current of the high-voltage circuit or low-voltage circuit into a low-voltage small current (generally 5A), and supplies the instrument and relay protection device to achieve measurement, measurement, protection and other functions.

In order to better match the range of the instrument, there are also transformers that convert a small current below 5A into a large current (5A).

Transformer is a general term for current transformer and voltage transformer.

Turning high voltage into low voltage and high current into small current for measurement or protection of the system.

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An instrument transformer is a device that converts voltage or current proportionally. Its function is mainly to convert high voltage or high current into standard low voltage (100V) or standard low current (5A or 10A, both refer to rated values) in proportion, so as to realize the standardization and miniaturization of measuring instruments, protection equipment and automatic control equipment. At the same time, the transformer can also be used to isolate the high-voltage system to ensure the safety of people and equipment.

A device that converts voltage or current proportionally.

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The working principle of the transformer is somewhat similar to the principle of electromagnetic induction, which is also the way of winding, and the actual current and voltage in the line can be calculated through measurement and calculation. Transformer is also known as instrument transformer, which is a general term for current transformer and voltage transformer. It can turn high voltage into low voltage and high current into small current for measurement or protection system.

In the power supply line, the current difference is from a few amperes to tens of thousands of amperes, and the voltage difference is from a few volts to several million volts. The current and voltage in the line are relatively high, and it is very dangerous to measure it directly. In order to facilitate the measurement of secondary instruments, it is necessary to convert the current and voltage into a more uniform current and voltage, and the transformer is used to play the role of converter and voltage transformation and electrical isolation.

Most of the display instruments are pointer-type current and voltmeters, so most of the secondary currents of the current transformer are amper-level (such as 5, etc.). With the development of the times, most of the electricity measurement has reached the digital level, and the signal sampled by the computer is generally at the milliampere level (0-5V, 4-20mA, etc.). The secondary current of the miniature current transformer is milliampere, which mainly plays the role of a bridge between the large transformer and sampling.

The miniature current transformer is called "instrument current transformer". ("Instrument current transformer" has a meaning of multi-current ratio precision current transformer used in the laboratory, which is generally used to expand the range of the instrument.) ）

1. The function of the transformer is to reduce the AC voltage and high current to the value that can be directly measured by the instrument in proportion, which is convenient for the direct measurement of the instrument, and at the same time provides power supply for relay protection and automatic devices.

2. The transformer for power system is a special transformer that transmits the information of high voltage and high current of the power grid to the secondary side of low voltage and small current, and the metering, measuring instrument and relay protection and automatic device of the low voltage and small current, and is the connecting element of the primary system and the secondary system, and its primary winding is connected to the power grid, and the secondary winding is connected with the measuring instrument and protection device respectively.

3. The transformer cooperates with the measuring instrument and metering device to measure the voltage, current and electric energy of the primary system; In conjunction with relay protection and automatic devices, it can constitute electrical protection and automatic control of various faults in the power grid. The performance of the transformer directly affects the accuracy of power system measurement and metering and the reliability of the operation of relay protection devices.

The transformer can reduce the AC voltage and high current to a value that can be measured directly by the instrument, which is convenient for direct measurement by the instrument, and at the same time provides power for relay protection and automatic devices. The transformer is divided into two categories: voltage transformer and current transformer, voltage transformer can be used for voltage and power measurement in high-voltage and ultra-high-voltage power systems, etc., and current transformer can be used for the measurement of exchange current, the measurement of exchange power and the protection of electric combustion finger force drag line.

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.