The role of current transformer

Current transformer is an instrument where the current at both ends affects each other. So the question is, what is the role of current transformer? Measurement? Protection? Let's take a look at it together~~

1. The role of current transformer - Introduction

Current transformer, the English name is Current transformer, the symbol is TA, is an instrument that can convert a large primary current into a small secondary current based on the principle of electromagnetic induction, consisting of a closed iron core and windings. Its structure is shown in the figure below. The primary winding has fewer turns and is connected in series in the circuit that needs to measure the current, while the secondary winding has more turns and is connected in series in the measuring surface or protection circuit. When it is in working condition, the secondary circuit of the current transformer is closed (otherwise there will be safety hazards), and the impedance of the series coil of the measuring surface or protection circuit is very small, making its working condition close to short circuit.

2. The role of current transformer 1 - Used for measurement

One of the functions of current transformer is to be used for measurement, which is often used for billing or measuring the current size of running equipment. When measuring large alternating currents, in order to facilitate surface measurement and reduce the danger of directly measuring high voltage electricity, it is often necessary to use a current transformer to convert it into a more uniform current. Here, the current transformer plays the role of current conversion and electrical isolation. The current transformer converts high current into low current in proportion as required. When used for measurement, the primary side of the current transformer is connected to the primary system, and the secondary side is connected to the measurement surface or relay protection equipment.

3. The second function of the current transformer - used for protection

The second function of the current transformer is to be used for protection. It is often used in conjunction with relay equipment. When the line has a short circuit or overload, the current transformer sends a signal to the relay equipment to cut off the faulty circuit, thereby achieving the purpose of protecting the safety of the power supply system. The protective current transformer is different from the measuring current transformer. It can only work effectively when the current is several or dozens of times larger than the normal current, and it requires reliable insulation, a satisfactory large accuracy limit coefficient, and satisfactory thermal stability and dynamic stability.

IV. The role of current transformer - Precautions

1. During the operation of the current transformer, the secondary side is not allowed to be open and must be kept closed. Because once the secondary side is open, the magnetic flux and the secondary side voltage will far exceed the normal value (up to thousands or even tens of thousands of volts), which is extremely harmful to the safety of operators and equipment.

2. The wiring method of the current transformer should follow the series principle, that is, the primary winding is connected in series with the measured circuit, and the secondary winding is connected in series with the measuring surface or relay device.

Hemei Electronics has been professionally developing and producing current transformers for many years. If you want to know more information, please feel free to contact us!