For power novices who have just come into contact with transformer knowledge, there are always some confusing knowledge points in a large number of basic concepts. Transformer no-load operation in transformer load operation is one of them. Although there are a lot of materials to explain the two concepts separately, few materials will explain the difference between the two.
This paper will introduce transformer no-load and transformer load operation respectively, and explain the difference between them. Let's have a look with the small series.
No load operation of transformer
This refers to the working state in which the primary winding of the transformer is connected to the power supply and the secondary winding is open circuit. At this time, the current in the primary winding is called the no-load current of the transformer. No load current produces no-load magnetic field. Under the action of the main magnetic field (i.e. the magnetic field crosslinking the primary and secondary windings at the same time), the electromotive force is induced in the primary and secondary windings.
During no-load operation, although there is no power output at the secondary side, the primary side still absorbs part of the active power from the power grid to compensate the hysteresis loss and eddy current loss in the iron core caused by flux saturation, which is referred to as iron loss for short. The magnitude of hysteresis loss depends on the frequency of power supply and the area of hysteresis loop of iron core material; Eddy current loss is proportional to the square of magnetic flux density and frequency. In addition, there is copper loss caused by no-load current. For transformers with different capacities, the no-load current and no-load loss are different.
Transformer load operation
It refers to the working condition when the primary winding is connected to the power supply voltage and the secondary winding is connected to the load. At this time, the secondary side of the transformer also has current flow, the access circuit of the original transformer increases correspondingly compared with no-load, and the secondary side terminal voltage will change under the influence of load.
Operation under normal periodic load:
1. Under rated service conditions, it can operate at rated current throughout the year. 2. It is allowed to periodically exceed the rated current when the average relative aging rate is less than or equal to 1.
3. When it has serious defects (such as abnormal cooling system, serious oil leakage, local overheating, abnormal analysis results of dissolved gas in oil, etc.) or weak insulation, it is not suitable to operate above the rated current.
4. Under normal periodic load operation mode and over rated current operation, the allowable load factor K2 and time can be determined according to one of the methods in the load guidelines.
The difference between the two
The main difference between no-load operation and load operation of transformer is mainly reflected in the secondary coil. When the transformer is under load, the secondary coil is connected to the load and generates large power. When the transformer is under no-load operation, the secondary coil is open circuit and generates micro power.
It is a device that uses the principle of electromagnetic induction to change AC voltage. The main components are primary coil, secondary coil and iron core (magnetic core). In electrical equipment and wireless circuits, it is often used for voltage rise and fall, matching impedance, safety isolation, etc. During no-load operation of the transformer, only no-load loss, i.e. iron loss and stray, is consumed, which is 6% of the total capacity. During load operation, it is no-load loss + load loss, i.e. copper loss, which is the total consumption of the transformer.
This paper introduces the no-load operation and load operation of transformer respectively, and explains the differences between them in detail after completing the groundwork of basic knowledge. It is a very suitable article for novices to read. I hope all friends who have questions about no-load and load can solve their confusion after reading this article.