Calculation method of transformer capacity
Writer： Hengfeng you electric Time：2023-04-07 views：times
According to the existing data, the design and calculation of power transformer capacity are determined according to the load rate. And its load rate generally ranges from 60% to 90%. The optimal economic capacity of transformer can not be calculated, so it can not operate in the optimal economic area. This will increase the loss of active and reactive electric energy. Therefore, we calculate accurately and determine the optimal economic capacity of the transformer, so as to make it operate in the optimal economic area, so as to reduce the loss of active power and reactive power.
1. Basic overview of transformer
Transformer is a device that uses the principle of electromagnetic induction to change AC voltage. The main components are primary coil, secondary coil and close core (magnetic core).
The main functions of the transformer include voltage conversion, current conversion, impedance conversion, isolation, voltage stabilization (magnetic saturation transformer), etc. Transformers can be divided into power transformers and special transformers (electric furnace transformer, rectifier transformer, power frequency test transformer, voltage regulator, mining transformer, audio transformer, medium frequency transformer, high frequency transformer, impulse transformer, instrument transformer, electronic transformer, reactor, transformer, etc.) according to their purposes.
2. Function of transformer
There are generally two functions of transformer, one is voltage rise and fall, and the other is impedance matching. Let's talk about the voltage rise and fall first. Usually, there are many kinds of voltages we use, such as 220V for domestic lighting, 36V for industrial safety lighting, and the voltage of electric welding machine needs to be adjusted. These are inseparable from the transformer. The transformer can reduce the voltage to the voltage we need through the principle of electromagnetic mutual inductance of main and auxiliary coils. In the process of long-distance voltage transmission, we need to raise the voltage to a very high level to reduce the loss of voltage, usually up to thousands of volts, which is the role of transformer.
Impedance matching: the most common is in electronic circuits. In order to connect the output and input signals without resistance, voltage devices are usually used for impedance matching. For example, in old-fashioned broadcasting, because constant voltage output is adopted and the speakers are high resistance speakers, only output transformers can be used for matching. Therefore, transformers are inseparable from daily life and industrial production.
3. Calculation method of conventional transformer capacity
According to the power engineering design manual, the transformer capacity shall be selected according to the calculated load. For a single transformer with stable load power supply, the load rate is generally about 85%.
Namely: β= S/Se
Where: s -- calculated load capacity (kVA); Se - transformer capacity (kVA); β—— Load rate (usually 80% ~ 90%).
The total power of each box is 10kW, the total load of each box is 9kw, and the maximum load of each box is 9kw. The total load of each box is 9kw. (Note: the power of each equipment in a single box is calculated according to the maximum value on the nameplate. The power of three boxes of equipment divided by 3 is equal to the power of each box of this equipment)
For example: total load power of box C = (300W * 10 sets of milk) + (2kW * 4 sets of air conditioners) = 11kw
Calculated total power of three tanks: 11kw * 3 tanks = 33kw (total power of three tanks of transformer)
The total power of three boxes is 0.8, which is the most important step. At present, more than 90% of the transformers sold on the market have a power factor of 0.8, so it needs to be divided by the power factor of 0.8.
33kw / 0.8 = 41.25kw (total power of transformer)
41.25kw / 0.85 = 48.529kw (transformer power to be purchased), then 50KVA transformer can be selected at the time of purchase.
4. Precautions
Firstly, the rated capacity of the transformer should be the maximum load apparent power that can ensure the normal operation of the transformer under the specified service conditions; Then, the apparent power is the output power of the transformer and the apparent power that the transformer can carry the maximum load; And when the transformer is in rated operation, the output apparent power of the transformer is equal to the rated capacity; When the transformer is in rated operation, the input apparent power of the transformer is greater than the rated capacity.
