Several important knowledge points of three-phase transformer
Most important equipment will use an important component-three-phase transformer. Such transformers often appear in mechanical equipment, medical equipment and other equipment. For some distinguished equipment, its existence is undoubtedly the icing on the cake, because its output voltage, adjustment taps and other values are more in line with the use of these distinguished equipment. Here are some important points that are more practical.
I. Determination of winding polarity
First introduce the measurement of the transformer. Compared with ordinary transformers, when measuring its polarity by the DC method, for safety reasons, low-voltage dry batteries, batteries, DC ammeters and DC voltmeters are often used to switch on the high-voltage windings of the transformer. At the moment of DC power supply, the polarity of each winding end of the transformer is determined according to the positive and negative directions of the low voltage winding current and voltage.
Second, winding head and tail judgment
According to the company with a guaranteed after-sales service of the transformer, if we designate 1U1 as the head of the high-voltage winding, 2U1 or 2U2 (pointer reverse bias) with the same name as 1U1 is the head of the low-voltage winding. The tail end is the remaining pair of terminals. That is, a coil penetrated by the same alternating magnetic flux, and the same polarity (the same end with the same name) has the same head and tail (the same head or tail). For a winding, which end point is positive polarity, but once it is determined, the exchange with other magnetic coils is determined according to the relationship of the end with the same name, and the end is also determined. Judging the three-phase transformer will be more convenient.
Third, polarity and head and tail judgment
In a three-phase transformer, the determination of the same-named ends between the primary and secondary windings of each phase is the same as for a unidirectional transformer, and the relationship with the head and tail ends is still the same polarity (the same end with the same name), and it follows the relationship with the head-end. However, strictly speaking, the three-phase windings do not belong to the category of the same-named ends. Because the windings are wound on different iron cores and have their own magnetic flux, there is no relationship of the same-named ends. However, according to the symmetry requirements of the three-phase magnetic field, there is also a head-to-tail discrimination problem.
Although the three-phase transformer's polarity and end-to-end are judged by the DC method, many methods can still be used to judge. But the direct current method is a more intuitive and accurate judgment method, which can be better reference.