Power transformers are used in series and in parallel

The power transformer is the same as the general device. In emergency operation, multiple transformers can be used in series and parallel under certain conditions. For example, a commercially available power transformer can fully meet the requirements. When the power of the transformer meets the requirements, and there is no suitable voltage, two or more transformers can be used in series; when the voltage is satisfied, and the power of the transformer is not enough, two or more transformers can be used in parallel to meet Circuit power requirements. The power transformer is composed of an inductor coil, so the transformer can be connected in series with the primary of the power transformer or in the secondary of the output. The four cases are described below.

1. The primary series of power transformers.

In the transformer calculation formula, there is a constant N called the turns ratio, which is the ratio of the primary turns to the secondary turns. The primary to secondary voltage ratio is N, and the primary to secondary current ratio is 1/N. For example: two primary 220V, secondary 18V transformer, N is 13, if the primary of the two transformers are connected in series, the output voltage will drop below 9V on a single secondary. In this case, two or more transformers can be used in series in the case where the secondary voltage of a single transformer is higher than that of a multiple power supply. And if you connect the two sub-lines in series, there is not much use value. In this case, as long as the power requirement of a single transformer is guaranteed, the secondary output voltage is not necessarily the same, and its output voltage is calculated as: V single = (V1 times + V2 times + ... Vn times) / Vn.

2. The secondary connection of the power transformer.

The secondary series of power transformers is a combination of two or more transformers when the single power is satisfied and the secondary output voltage is not met. For example, when the primary input of two transformers is 220V and the secondary output is 18V, if the load is supplied with 33V, the secondary of the two transformers can be used in series. The secondary series connection of the power transformer is also very easy, and the different secondary outputs can be applied in series in parallel as long as the power of the individual transformer is guaranteed. In the ideal situation, when the primary input voltages of multiple transformers are the same, the total output calculation formula is: V total = V initial order / (V1 times + V2 times + ... Vn times).

3. The primary parallel connection of the transformer.

This kind of situation is a common example in our life. The remote transformer and the main transformer (power switch transformer) in the old-fashioned color TVs with different power supply are all connected in parallel with the primary of the transformer.

4. The secondary of the transformer is connected in parallel.

The secondary shunting of the power transformer is the application where the output voltage of the single transformer secondary is the same and a single power cannot be met. Its application is to superimpose the secondary currents of multiple transformers to meet the power requirements of the load. The secondary parallel connection of the power transformer allows the output power to be the sum of the powers of multiple transformers.

The series-parallel application of the power transformer is independent of the linear power circuit and circuit. In the previous linear power supply circuits, there were more applications in the secondary series, such as the line-reverse transformer in the TV set, which used the series connection of the transformer secondary. In the current high-power switching power supply, the application of the secondary parallel connection is more. In the above-mentioned one-hundred-watt switching power supply, the secondary of the transformer is often connected in parallel to increase the power. Pay attention to the following points when applying series and parallel connection of power transformer:

(1) When the power transformer is connected in series and parallel, pay attention to the same name of the transformer. When it is used in series, it must be serialized and cannot be reversed. When used in parallel, the same name and the same name should be used together, otherwise the transformer will be burnt.

(2) The above calculations are only ideal algorithms, but in practice the individual transformer losses after their series-parallel connection are very large. The secondary output voltage of each power transformer will be lower than the above calculation.

(3) Different secondary outputs, if used in parallel, are preferably performed after voltage regulation, and the parallel voltage is the lowest voltage value in the transformer output. In the case of secondary series application, it can be a secondary direct series connection, or it can be connected in series after voltage regulation.

(4) Common ground in the power supply circuit is necessary. The potential comparison and voltage calculation can only be performed under the condition of a reference point.