Te rahi transformer mai i te demand
Whakaritea te rahi o tētahi transformer mai i te demand, me te tupu me ngā ngaronga.
Whakamātau mahi 4
Ka whakakī ia mahi i ngā uara tauira. Whakakapia ērā ki ō uara.
- 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.
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Maximum Demand
- 220
- Tono ki roto
- kVA
- Power factor
- 0.9
- Tāpui tipu
- 20 %
- Te nuinga o te utanga i te utanga hoahoa
- 100 %
- Ngā wāhanga
- Wāhanga toru
- Voltage tuatahi
- 11,000 V
- Whakahiato tuarua
- 400 V
- Impedance
- 4.5 %
- Tauwhāinga X/R
- 4
- Ngaronga kore utanga, o te ine
- 0.2 %
- Ngaronga utanga i te utanga katoa, o te ine
- 1.1 %
Te rahi o te transformer
300kVA
- Te utu hoahoa me te tipu
- 264kVA
- Te utu i tēnei rā
- 73.3%
- Te utu me te tipu
- 88%
- Te whakarite voltage me te tipu
- 2.59%
- Ngā ngaronga me te tipu
- 3.16kW
- Au utu katoa tuarua
- 433.01A
- Au hapa tuarua
- 9,622.5A
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Utu hoahoa me te tipu 20 %264kVA
- Te rahi iti rawa tōtika i te utaina 100 %300 kVA
- Te utu i tēnei rā73.3%
- Te utu me te tipu88%
- Ōkeroa, o te reiti1.09%
- Reactance, o te reiti4.37%
- Te whakarite voltage me te tipu2.59%
- Voltage tuarua i te utu hoahoa389.7V
- Ngā ngaronga me te tipu3.16kW
- Pai me te tipu98.69%
- Au kawe kī katoa tuarua433.01A
- Au hapa tuarua9,622.5A
Mō tēnei tātaitai
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.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
Me pēhea te rahi o tētahi transformer?
Tīmatahia mai i te maximum demand, tāpiri he whakaaetanga mō te tupu, ā, kōwhiria te reiti paerewa iti rawa e kawe ai te putanga. Kātahi arotakehia te voltage e heke ana te transformer i taua uta, me te wera e ngaro ana hei pūngao.
He pēhea te tupu me whakaaro ai au?
It depends on the site. 20 to 30 % is common where more load is likely. A transformer lasts decades, and changing it later costs more than one size up now.
He aha te whakarite voltage transformer?
Ko te heke o te voltage secondary mai i te kore uta ki te uta, hei ōrau. Ka ahu mai i te aukati me te reactance o te transformer, ā, he nui ake ina iti te power factor.
He aha te kore e kōwhiri noa i tētahi transformer tino nui?
He utu nui ake te waeine nui ake, ā, ka rere tōna ngaronga core i te rā katoa, ia rā, ahakoa he uta māmā. Ina rahi tata ki te uta, ka mahi te transformer ki te wāhi e iti rawa ai ōna ngaronga mō te pūngao e tukuna ana e ia.
Nō hea mai te impedance me ngā ngaronga?
Kei te rating plate te impedance. Kei te pūrongo whakamātautau a te kaihanga ngā ngaronga me te X/R ratio. Ko ngā taunoa o te taputapu he tauāhua tauira kia rite ai ngā mea pono.
Ngā taputapu hononga
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