1.Impulse current of R-type transformer

When the secondary side of the transformer is opened and the rated voltage is applied to the primary side, the primary current has an instantaneous impact process, which is called the impulse current. The duration of the impulse current is very short. Under the usual 50Hz condition, the current will last for 1/4~1/2 cycle, that is, 5ms~10ms, and then it will enter a stable state.

Ten times the rated current within a few milliseconds will not damage the insulation material and windings.

The R-type transformer has the characteristics of relatively large impulse current. There are the following methods to reduce the impulse current:

(1)It can reduce the magnetic flux density of the iron core, increase the number of turns of the primary winding, and reduce the saturation degree of the iron core when the transformer is closed with no load, thereby reducing the impulse current, but the premise is that the power of the transformer is sacrificed.

(2)The R-type transformer with higher power can use the winding method of the primary winding on the outer layer and the secondary winding on the inner layer to reduce the impulse current.

2.Protection of R-type transformers

The overcurrent protection of transformer protection can be further divided into short circuit protection and overload protection. The fuse protector can only play the role of short-circuit protection. For the problem of impact, the fuse protector used in the primary stage of the transformer can use a time-delay fuse, or its rated current can be 3 to 3.5 times the rated current of the transformer.