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Principle of Current Transformer

There are many beginners who do not understand the working principle of current transformers. The current transformer is actually a small current transformer, which turns the large current in the circuit into a small current that can be measured and measured. It is mainly suitable for current monitoring and meter measurement, and can also provide working power for relay protection. , such as thermal relays, etc.


The current transformer is composed of a closed iron core and two windings wound on the same iron core, and is divided into a primary winding and a secondary winding. The primary side winding has few turns and needs to be connected in series in the circuit under test, while the secondary side winding has more turns and is connected in series in the measuring instrument and the protection circuit. When the primary side winding passes a large current, the secondary winding wound on the same concentric induces a small current required for current measurement and circuit protection according to the principle of electromagnetic induction.


The operating current of the ammeter, watt-hour meter, numerical value, and thermal relay protection that we usually see is provided by the secondary side of the current transformer, and some are small currents.


Transformers can be directly connected in series in the circuit being measured, but some cannot. Because the current directly connected in series in the circuit under test is relatively small and the cable is relatively thin, it can be directly connected to the primary side winding of the current transformer. However, if the current of the circuit under test is very large, tens of amps, hundreds or even thousands of amps, the capacity of some ammeters is too small, so it cannot be directly connected in series to the circuit under test.


The toroidal core of the current transformer passes through the center, and the wire passing through the center is the primary winding. How should the current be calculated if it is used in conjunction with a current transformer? Current transformers all have a certain transformation ratio, such as 50:5, 200:5 or 400:5, etc.


When selecting an ammeter, its ratio must be the same as that of the transformer, so that the reading of the ammeter can be Be more accurate.


For example, for a 300:5 current transformer and ammeter, if the feedthrough cable is a turn of the real ammeter, the reading is 250 amperes, which is the actual current value of the device being measured, and the ammeter is 150:5. Then the cable through-core turns of the current transformer is two turns, and so on, but one thing, the through-core turns must be divisible by 300, otherwise the current reading will be inaccurate. When measuring electric energy, multiply the ratio of the transformer by the reading of the electric meter.


For example, if the reading of the electric meter is 100, the current magnification of the transformer is 200: 5, and its magnification ratio is 40. When 40 times 100 equals 4000, the actual power consumption should be is 4000 kWh. This is the simple electrician's knowledge of how much electricity is used by the electricity meter through the current transformer. If you like, you can comment and leave a message


After Generac Acquires Pika Energy, Enters Energy Storage Market, Pika Current Transformer Kit can also be used for Generac Current Transformers


Premier Cable make a lot of RJ45 female socket to push button terminal blocks for Pika and Generac Current Transformers  


You can see the products details from below link :


If you need product details, drawings, and samples, you can use below contact info : 


Skype : James198585 

Wechat : 13929497934


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