根据需量确定变压器容量
根据需量，计入增长及损耗选定变压器。
尝试一个工程 4
每项工作都会预填示例数值。请替换为您自己的数值。
- Size a transformer for a new siteThe rating, loading and losses for a site demand with room to grow.
- Size a transformer from a kW demandA demand in kilowatts turned into the transformer rating at its power factor.
- Check a rural single‑phase transformerThe size and voltage drop of a single‑phase transformer for a farm supply.
- Check a plant transformer regulationThe voltage a large transformer drops at a low power factor.
输入
使用默认输入值的示例计算。
- 最大需量
- 220
- 输入负荷
- kVA
- 功率因数
- 0.9
- 增长余量
- 20 %
- 设计负荷下的最大负载
- 100 %
- 相
- 三相
- 一次侧电压
- 11,000 V
- 二次侧电压
- 400 V
- 阻抗
- 4.5 %
- X/R 比值
- 4
- 空载损耗，占额定值
- 0.2 %
- 满载负载损耗，占额定值
- 1.1 %
变压器容量
300kVA
- 含增长的设计负载
- 264kVA
- 当前负载
- 73.3%
- 含增长的负载
- 88%
- 含增长的电压调整率
- 2.59%
- 含增长的损耗
- 3.16kW
- 二次满载电流
- 433.01A
- 二次故障电流
- 9,622.5A
此结果仅供设计参考。请对照现行标准进行核验。
计算步骤
- 含 20 % 增长的设计负荷264kVA
- 100 % 负载率下的最小典型规格300 kVA
- 当前负载73.3%
- 含增长的负载88%
- 额定值的电阻1.09%
- 额定值的电抗4.37%
- 含增长的电压调整率2.59%
- 设计负荷下的二次电压389.7V
- 含增长的损耗3.16kW
- 含增长的效率98.69%
- 二次侧满载电流433.01A
- 二次侧故障电流9,622.5A
关于此计算器
How this is calculated
A transformer is sized from the maximum demand it will carry, with room for the load to grow. Too small and it runs hot and drops too much voltage; too large and it costs more and wastes energy in its core every hour of the year. This tool finds the size and shows what it does at the load.
You enter the maximum demand, in kVA or in kW with a power factor, and a growth allowance. The design load is the demand plus that growth. The tool picks the smallest rating from a list of typical sizes that carries the design load within the loading limit you set. The list is common distribution and site ratings, not a standard's list.
At that size it works the loading today and with growth, then the voltage regulation: the drop through the transformer's own resistance and reactance at the design load and power factor. The impedance on the rating plate splits into the two by the X/R ratio. The losses are the core loss, which is there whenever the transformer is energised, plus the winding loss, which rises with the square of the loading. The full load and fault currents at the size come from the transformer tool.
The impedance, X/R ratio and losses are maker's data. The defaults are typical figures, and the result names them as assumptions.
| Step | Table or clause | What it decides |
|---|---|---|
| Design load | Demand plus the growth allowance | The load the size must carry |
| Size | Smallest typical rating within the loading limit | The transformer rating |
| Resistance and reactance | Impedance split by the X/R ratio | The two parts of the drop |
| Voltage regulation | Loading times the drop at the power factor | The voltage lost through the transformer |
| Losses | Core loss plus winding loss times loading squared | The heat and the running cost |
| Currents | The transformer tool | The full load and fault current at the size |
Worked examples
- A 220 kVA site with 20 % growth needs a 300 kVA transformer. It runs at 88 % with growth and loses 2.59 % of its voltage.
- A 180 kW load at 0.85 power factor with 25 % growth also needs 300 kVA, at 88.2 % with growth.
- A 420 kVA factory with 30 % growth, loaded to 80 % at most needs 750 kVA, at 72.8 % with growth.
- A 60 kVA single‑phase rural supply with no growth needs 75 kVA, at 80 %.
- A 900 kVA plant at 0.8 power factor, 6 % impedance and X/R of 7 needs 1,250 kVA. Its regulation is 3.57 % at 82.8 % with growth.
Limits
The regulation is the drop through the transformer alone. The network upstream and the cables downstream add their own drop; the total voltage drop tool adds the cable parts. A tap changer or off-load taps can raise the secondary voltage to make up for it.
The tool does not cover transformers in parallel, harmonic loads, the temperature rise of the windings or the network company's own sizing rules for a supply transformer.
See also: Transformer, Maximum demand and Fault level at a board.
问题
结果仅供设计参考。请依据现行标准核对。
如何进行变压器选型？
从最大需量出发，预留增长余量，并选取能承载该结果的最小标准额定值。随后检查该负荷下变压器的电压降，以及其以热量形式的损耗。
应预留多少负荷增长？
这取决于现场。若可能增加负荷，通常取 20 % 至 30 %。变压器使用寿命可达数十年，日后更换的成本高于现在选大一号。
变压器电压调整率是多少？
从空载到满载时二次侧电压的下降，以百分比表示。它取决于变压器的电阻和电抗，在低功率因数下更大。
为何不直接选用大得多的变压器？
容量过大的变压器造价更高，其铁芯损耗全天候持续，即使轻载亦然。变压器选型接近负荷时，其在所输出电能下的损耗最低。
阻抗和损耗数据来自哪里？
阻抗标注在铭牌上。损耗和 X/R 比值载于制造商的测试报告中。在获得实际数值之前，工具采用的是典型默认值。
相关工具
这是否有用？
有问题，或数值看起来有误？联系我们。