For newcomers who are new to the transformer, there must be confusion about the concept of power supply. The no-load and load of the transformer are obvious examples. The following small series will explain the no-load and load of the transformer in detail, and explain the difference between the two in detail.
Transformer no-load operation
The no-load operation of the transformer 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. At this time, the current in the primary winding is called the no-load current of the transformer. The no-load current produces an idling magnetic field. Under the action of the main magnetic field (that is, the magnetic field of the first and second windings simultaneously), the electromotive force is induced in the primary and secondary windings.
When the transformer is running at no load, although there is no power output on the secondary side, the primary side still draws a part of the active power from the grid to compensate for the hysteresis loss and eddy current loss caused by the magnetic flux saturation. The magnitude of hysteresis loss depends on the frequency of the power supply and the area of the hysteresis loop of the core material; the eddy current loss is proportional to the square of the maximum flux density and frequency. In addition, there is also copper loss caused by no-load current. For transformers of different capacities, the magnitude of no-load current and no-load loss are different.
Transformer load operation
The load operation of the transformer 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 flowing, and the original access circuit increases correspondingly to the no-load, and the secondary side voltage is affected by the load.
Normal periodic load operation:
1. Under the rated conditions of use, the transformer can be operated at rated current throughout the year;
2. The transformer allows periodic over-rated current operation when the average relative aging rate is less than or equal to one;
3. When the transformer has serious defects (such as abnormal cooling system, serious oil leakage, local overheating, abnormal analysis result of dissolved gas in oil, etc.) or weak insulation, it is not suitable for over-rated current operation;
4. Under normal cyclic load operation mode, the allowable load factor K2 and time during over-rated current operation can be determined according to one of the load guide methods.
The difference between the two
The main difference between the no-load operation of the transformer and the load operation is mainly reflected in the secondary coil. The secondary load of the transformer load is connected to the load, and the generated power is large. The secondary coil of the no-load operation is open, generating micro-power.
The transformer uses the principle of electromagnetic induction to change the AC voltage. The main components are the primary coil, the secondary coil and the core (core). It is often used as boost/buck, matched impedance, safety isolation, etc. in electrical equipment and wireless circuits. When the transformer is running at no load, it only consumes no-load loss, that is, iron loss and spur, which is 5% of the total capacity. When the load is running, it is no-load loss + load loss, that is, copper loss, which is the total consumption of the transformer.
In this paper, the transformer no-load operation and load operation are introduced separately. After completing the basic knowledge, the difference between the two is explained in detail. It is an article that is very suitable for novices to read. I hope that friends who have doubts about the no-load and load can solve the confusion after reading this article.