No-Load Operation and Load Operation of Transformer

For newcomers who have just been exposed to transformer knowledge, there are always some confusing knowledge in a large number of basic concepts. One of these is the operation of the transformer and the load operation of the transformer. This text will introduce the operation of transformer no-load and transformer load respectively, and explain the difference between the two.

Transformer no-load operation
The unloaded operation of the transformer refers to the working state of the first winding of the transformer to the power supply and the open circuit of the two winding. At this time, the current in the one winding is called the no-load current of the transformer. The no-load current produces an unloaded magnetic field. The electromotive force is induced in the one or two windings under the action of the main magnetic field (i.e. the magnetic field crosslinking the one or two winding at the same time).

Transformer load operation
The load operation of the transformer refers to the working condition of the original winding which is connected to the power supply voltage and the auxiliary winding is connected to the load. At the same time, the secondary side of the transformer also has current distribution. The access circuit of the original transformer will increase correspondingly compared with the no load, and the secondary side voltage will be affected by the load.

Normal periodic load operation:
1. The transformer can operate according to the rated current under the rated use condition.
2. the transformer is allowed to run periodically over the rated current when the average relative aging rate is less than or equal to 1.
3. when the transformer has serious defects (such as abnormal cooling system, serious oil leakage, partial overheating, abnormal analysis results of dissolved gas in oil, etc.), or when insulation is weak, it is not suitable for overrated current operation.
4. Under normal periodic load operation, the allowable load coefficient K2 and time are allowed when the super rated current runs, which can be determined according to one of the methods of the load guide.

The difference between the both
The main difference between the transformer’s no load operation and the load operation is mainly reflected in the secondary coil. The secondary load of the transformer is loaded by the secondary coil, resulting in large power and no load running secondary coil.

The transformer uses the principle of electromagnetic induction to change the AC voltage device, the main components are the primary coil, the secondary coil and the core (magnetic core). In electrical and wireless circuits, it is often used as a lift voltage, a matching impedance, a safe isolation, and so on. No load loss is consumed when the transformer is running at no load, that is iron loss and stray. It is 6% of the total capacity. When the load is running, it is no load loss plus load loss, that is copper loss, that is the total consumption of transformer.

The transformer’s no load operation and load operation are introduced in this paper. After finishing the groundwork of basic knowledge, the difference between them is explained in detail, which is very suitable for beginners to read. I hope that all of you who have some questions about the load and the load can be unpuzzled after reading this article.