Guide: This article mainly introduces the working principle of current transformers . The so-called current transformers are the devices that sense the mutual current on the two coils. Let's take a look at the principle of operation. ~~~
1. Working principle of current transformer --Introduction
A current transformer (CT) consists of a closed core and a winding. Its primary winding turns are few, and the string is in the line of current to be measured. The number of turns in the secondary winding is relatively large, and is connected in series in the measuring instrument and the protection circuit. The current transformer acts as a variable current and electrical isolation. It is a sensor for obtaining electrical current information of the primary loop in secondary equipment such as measuring instruments and relay protection in the power system. The current transformer converts the high current into a low current and current. The transformer is connected to the primary system once, and the secondary side is connected to the measuring instrument and relay protection.
2. The working principle of current transformer --structural composition
The current transformer is composed of a primary coil, a secondary coil, a core, an insulating support, and an outgoing terminal. The core of the current transformer is made up of silicon steel sheets. The primary coil is connected in series with the main circuit, and through the measured current I1, it generates alternating magnetic flux in the core, so that the secondary coil induces the corresponding secondary current I2. . If the excitation loss is neglected, then I1n1 = I2n2, where n1 and n2 are the turns of the primary and secondary coils, respectively. The current transformer has a current conversion ratio of K=I1/I2=n2/n1.
Since the primary coil of the current transformer is connected in the main circuit, the primary coil must be grounded to an insulation material compatible with the primary line voltage to ensure the safety of the secondary circuit and the human body. The secondary circuit is composed of a secondary coil of the current transformer, a meter, and a current coil of the relay in series. Current transformers can be roughly divided into two categories, current transformers for measurement and current transformers for protection.
3. Current transformer working principle
The principle of the current transformer is based on the principle of electromagnetic induction. Its primary winding often has all the current flowing through the line. 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 small and the operating state of the current transformer is close to a short circuit.
In an ideal current transformer, if the no-load current I0=0 is assumed, the total magnetomotive force I0N0=0, according to the law of conservation of energy, the primary winding magnetomotive force is equal to the secondary winding magnetomotive force, ie
I1NI=-I2N2
That is, the current of the current transformer is inversely proportional to its number of turns, and the ratio of the primary current to the secondary current I1 /I2 is called the current ratio of the current transformer. When the secondary current is known, the primary current can be obtained by multiplying the current ratio, and the phasor of the secondary current differs from the phasor of the primary current by 1800.
Expand reading:
The role of current transformers - measurement? Protection?
Current transformer basics
Classification of current transformers
Transformer
Ningbo Autrends International Trade Co.,Ltd. , https://www.mosvapor.com