Talking about how to connect transformer core grounding

Transformers, I believe we have all seen, large, small, square, round, line of transformers filled with all corners around us. From small appliances to small appliances, large power transformers supply power stations. As the saying goes, the sparrows are small and complete. The principle of the transformer is the same regardless of its size. It uses the principle of electromagnetic induction to change the current. It consists of a primary coil, a secondary coil, and a core. It is often used to raise and lower voltages, safe isolation and other fields. However, we will find a problem. Why do we need to ground the transformer core ? Let me explain the transformer core grounding related knowledge for everyone!

Transformer core introduction

The transformer core, which is responsible for the magnetic circuit in the line. Most of the transformer cores on the market today are made of silicon wafers, but a few of them are made of magnetic disks (chips made of magnet disks are gradually being eliminated).

Transformer core function

The role of the transformer core is mainly in two aspects: hysteresis loss and eddy current loss, respectively.

1. Hysteresis loss, which refers to the occurrence of iron loss due to hysteresis when the transformer is operating in the AC state, and the use of the transformer core can change this phenomenon to some extent. It can also ease the rise of the transformer's surface during operation.

2, eddy current loss, refers to the transformer in the work of the alternating current, it and the magnetic flux generated in the core of the induced current will change, this change we will call it eddy currents. The eddy current will increase the temperature of the iron core surface at the time of depletion, but because of the material (silicon) of the iron core, during this process, our resistivity will increase, which can reduce the effect of eddy currents.

Transformer core classification

It can generally be divided into four major categories: shell and core core, single-phase and three-phase iron core, three-dimensional and planar and stacked core and wound core.

Transformer core composition

It is mainly composed of three parts, namely the body, fasteners and insulation.


Transformer core section calculation

The transformer power calculation is calculated based on the cross-sectional area of ​​the core center column, the size of the core window, and the input voltage and output voltage. The number of turns is calculated based on the cross-sectional area of ​​the core and the input voltage. Then calculate the wire gauge (wire diameter of the enameled wire) according to the window size and number of turns, and then calculate how much current can flow according to the wire diameter. Calculate his power. According to the formula:

Turn left | Turn right N=4.4fbs/10 4

In the formula, N is the number of turns, f is the frequency, and B is the magnetic flux density of the silicon steel sheet. Generally, 10000 gauss is used as the standard, and s is the voltage. The number of calculations is calculated step by step.

Transformer core power calculation

P(W)=S(mm)2=19*19=361w. It is possible to make single-phase 220V transformers with a capacity of 300VA. It is known that the core section is 19 square millimeters, and the core is made of silicon steel sheet with a hafnium content of 9000 gauss to select Anzabi, 45/19=2.37 takes 3 turns per volt, and the primary winding is 3*220=660 turns. Winding 3*12=36 turns. The cross-sectional area of ​​the primary line is selected, the current is 300VA/220=1.36A, and the current passing through the square is 5A to consider = 1.36/5=0.28mm2 of the optional wire diameter of 0.6mm enameled wire. Secondary line cross-section area is selected, 300/12=25A 25/5=5mm 2 Enameled wire with an optional wire diameter of 2.6mm. If the iron core has a surplus, then the diameter of the first and second line can be selected again.

Transformer core grounding

During the use of the transformer, parts and components around the core and the core are in a strong electromagnetic field. Therefore, the impact of the electric field on the core itself will have a high ground potential, if the core and the ground There is no connection between the wires, then there will be a potential difference between the core and the ground, which will produce intermittent discharge. And there will be a strong electromagnetic field near the windings. In this way, the iron core and the components are in the unequal magnetic field, and there is a potential difference between them. Perhaps the potential difference is not great, but it is enough. Breakdown of small insulation gaps, so that there will be continuous discharge phenomenon. This is absolutely not allowed in power management. It is also difficult to check if you want to prevent this phenomenon, because some small insulation gaps are invisible to the naked eye. Therefore, we must connect the iron core to the ground.

How to connect transformer core grounding

The grounding of the core is usually grounded at one point. The steel sheets in the core are not energized to each other, so for safety reasons, we must not ground all the steel sheets. When the core is grounded, we only need to connect one of the steel plates to the ground, not all of them, because although the steel plates are not energized, if the steel plates are all connected to the ground, then The ground will become a conductor, making it possible to conduct electricity between the steel sheets, thereby disturbing the eddy currents. Therefore, a one-point grounding can both flow current to the earth without disturbing the eddy current, which also serves the purpose of grounding the core.


Transformer core manufacturer

Guangdong Haihong Transformer Co., Ltd. specializes in producing three-dimensional core transformer core, is currently the largest manufacturer of three-dimensional coil core. The single-phase coil core distribution transformer produced by the company is a single-phase, three-wire product and has passed all types of tests and other tests. The low-voltage voltage combination of this transformer is 2×0.23kV, and its principle and use are different from ordinary single-phase two-wire transformers. The low-voltage current of this kind of transformer is only half of the rated current of the ordinary single-phase transformer (the voltage of a1-a2 is 2 times of 230V, so the current is only half), and the biggest benefit is that the line loss of the former is only for the latter. Of the 1/4, which is why the majority of foreign countries use the single-phase transformer. The product implements national standards GB1094 "Power Transformers" and GB/T6451 "Three-phase oil-immersed power transformer technical parameters and requirements" and JB/10317-02 "Single-phase oil-immersed distribution transformer technical parameters and requirements."

Shandong Liaocheng Transformer Co., Ltd. is very good. It is a manufacturer of power transmission and distribution equipment and high and low voltage complete sets of power equipments, mainly producing power transformers, dry-type transformers, American box transformers, and European-style box transformers. The company is located in a historical and cultural city in China. Located in Liaocheng City, Shandong Province, Jiangbei Shuicheng and Liaocheng University, it is 90 kilometers away from Jinan, the capital city of the province. It is also connected by highways and railways. The Beijing-Kowloon Railway and the Ji-Ji Railway meet here. The transportation is very convenient.

Editor's summary: It is one of the indispensable machines in industrialization, and after our introduction above, everyone should know that the most important thing in the transformer is the quality of the iron core. Therefore, everyone must pay attention to whether the core in the transformer is qualified when purchasing.

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