Dry Type Transformer Rated Current

The rated current is the current of electrical equipment working with rated voltage and rated power. Electrical equipment is defined as the current that runs continuously for a long time in environmental conditions (ambient temperature, sunshine, altitude, installation conditions, etc.). The current of the device during normal operation cannot exceed its rated current.

In the case of dry-type transformers working with fixed capacity, the winding current is used as the fixed-rate current, and the overload dry-type transformer can be operated according to the Load Guide for Power Dry-type Transformers of the national standard GB/t 51641-1994. In the case that the rated capacitance of three-phase is not more than 100 MVA (single-phase is not more than 33.3 MVA), the load factor can withstand accidental overload below 1.5 (load current/rated current), and in the case of large capacity, the load factor Can withstand occasional overload below 1.3.

The calculation method of the rated current is to remove the coefficient corresponding to the rated capacity of the coil and the rated voltage of the coil (single-phase is 1, three-phase is 1√3). For this reason, the rated current of the dry-type transformer is the rated current of each coiled wire, which refers to the line current. However, for a single-phase dry-type transformer composed of three-phase groups, in the case where the coiled wire is delta-connected, the The freeze-frame current takes the line current as the numerator and √3 as the denominator. For example, if the line current is 500 A, the lines current rating is (500/√3)A.