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## Electrical knowledge

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Update time : 2018-07-27 09:10:51
For newcomers who have just come into contact with the transformer, there are always some confusing points of knowledge in a large number of basic concepts. Transformer no-load operation and transformer load operation is one of them. Although there is a wealth of information to explain these two concepts separately, there is little information to explain the differences between the two.

This article will introduce the transformer load and transformer load operation respectively, and to explain the distinction between the two, let us take a look at it.

Transformer no-load operation refers to the transformer primary winding access to power supply, the secondary winding open the working condition. At this moment, the current in the primary winding is called the no-load current of the transformer. No-load current to produce no-load magnetic field. Under the action of the main magnetic field (that is, the magnetic field of one or two windings at the same time), the electromotive force is induced in the primary and secondary windings.

While the transformer is in no-load operation, although the secondary side has no power output, the primary side still draws a part of active power from the grid to compensate the hysteresis loss and eddy current loss caused by the magnetic flux in the iron core due to 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 no load current caused by copper consumption. For different capacity of the transformer, no-load current and no-load loss of the size is different.

Transformer load operation refers to the original winding access to the power supply voltage, vice around the work load when the load condition. At this time, the secondary side of the transformer also has current flow, and the original access circuit increases correspondingly with no-load, and the voltage on the secondary side will be affected by the load.

1, the transformer under rated conditions of use, the whole year can run at rated current.

2, the transformer allows the average relative aging rate is less than or equal to 1 cases, periodically over-rated current operation.

3, when the transformer has more serious defects (such as the cooling system is not normal, a serious oil leakage, the phenomenon of local overheating, dissolved gas analysis of the oil abnormalities, etc.) or insulation weaknesses, should not exceed the rated current operation.

4. Under the normal periodic load operation mode, when the over-rated current is running, the allowable load factor K2 and time can be determined according to the method of load guide.

The difference between the two

The main difference between the transformer no-load operation and load operation is mainly reflected in the secondary coil, the transformer load running secondary coil connected to the load, resulting in large power, no-load running secondary coil open, resulting in micro-power.

Transformer The principle of electromagnetic induction to change the AC voltage device, the main components are the primary coil, secondary coil and core (core). In electrical equipment and wireless circuits commonly used for voltage, matching impedance, safety isolation. Transformer no-load operation, only consume no-load loss, that is, iron loss and spurious, which is 6% of the total capacity, load operation is no-load loss + load loss, that is, copper loss is the total transformer consumption.