Tātaitai power factor correction
Kimihia te kvar o te capacitor hei whakapiki i tētahi power factor.
Reads AS/NZS 3000:2018.
Whakamātau mahi 10
Ka whakakī ia mahi i ngā uara tauira. Whakakapia ērā ki ō uara.
- Correct a factory power factorThe kvar and bank steps to lift a 250 kW load from 0.78 to 0.95.
- Free supply capacity with power factor correctionThe kVA a 400 kVA site gets back when its power factor rises to 0.98.
- Correct a motor boardThe kvar to lift a 75 kW motor load from 0.82 to 0.95.
- Choose the capacitor stepsThe bank in 25 kvar steps for a 300 kVA load.
- Check a bank for resonanceThe bank against the fault level and 20 % harmonic load.
- Correct a single‑phase loadThe kvar for a 15 kW single‑phase load at 0.7.
- Size a capacitor at a motorThe largest capacitor a pump motor can take, and its new line current.
- Correct a small motor at the motorWhy a small motor capacitor stops short of the target power factor.
- Cut the line current of a large motorThe current a capacitor at a large motor takes off its cable and starter.
- Check a motor capacitor for self-excitationThe no-load limit on a capacitor at a small conveyor motor.
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Whakatika
- He uta, he poari rānei
- Ngā wāhanga
- Wāhanga toru
- Voltage
- 400 V
- Wāhanga utanga
- kW
- Uta
- 100
- Tauwhāinga hiko o nāianei
- 0.75
- Tauwhāinga hiko whāinga
- 0.95
- Hikoi pēke
- 25 kvar
- Pōrearea harmonic o te au (THDi)
- 0 %
- Taumata hapa i te peke
- 0 MVA
Ka hiahiatia te whakatika
55.32kvar
- Pēke kua whakaurua
- 3 × 25kvar
- Tauwehe pūngao me te peke
- 0.991
- Au i mua
- 192.45A
- Au i muri
- 145.59A
- Kaha kua tukuna
- 32.47kVA
- Kaikawe pēke, iti rawa
- 146.14A
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Pūngao tūturu100kW
- Hiko reactive i te tauwehe pūngao o nāianei88.19kvar
- Hiko reactive i te tauwehe pūngao whāinga32.87kvar
- Me whakatikaHua55.32kvar
- Hikoi pēke
3 × 25 kvar
- Tauwhāinga hiko me te pēke kōhiko0.99
- Au i mua192.45A
- Au i muri145.59A
- Kaha tuku32.47kVA
- Au reitia o te peke108.25A
- Kaha iti rawa o ngā kaikawe peke, 135 %146.14A
AS/NZS 3000:2018 Cl 4.15.2.3
Mō tēnei tātaitai
How this is calculated
The tool finds the capacitor bank that lifts a load to a target power factor. It then gives the current before and after.
- Real power. You enter kW, or kVA with a power factor. The tool finds the real power.
- Reactive power. It finds the reactive power at the present power factor. It does the same at the target.
- Correction required. The difference is the kvar the bank must supply.
- Bank steps. It rounds up to whole steps of the size you enter. It then recalculates the power factor with that bank.
- Currents. It finds the current before and after. The difference is the capacity the bank releases.
- Bank conductors. It sizes the bank conductors at 135 % of the bank rated current. This follows AS/NZS 3000 Cl 4.15.2.3.
AS/NZS 3000 Cl 4.15.2.2 covers switching, and Cl 4.15.3.1 covers discharge.
Worked example
- 100 kW three‑phase load at 400 V, 0.75 to 0.95, 25 kvar steps. The correction required is 55.32 kvar. The bank is 3 × 25 kvar. The power factor with the bank is 0.991. Current falls from 192.45 A to 145.59 A. The released capacity is 32.47 kVA. The bank conductors need at least 146.14 A.
One motor
Set Correct to one motor to size a capacitor fitted at a motor and switched with it. The capacitor must not supply more than the motor's own magnetising kvar. If it does, the motor, still turning after it is switched off, can excite itself from the capacitor and raise its voltage. The tool takes the no-load current as all magnetising and keeps the capacitor to 90 % of the no-load kvar, a rule of practice. It fits the smaller of that and the kvar to reach the target at full load, then gives the line current with it from the motor tool's full load current.
- A 30 kW motor at 0.85 with 17 A no-load current can take 10.6 kvar at most. The 9.7 kvar to reach 0.95 fits, and the line current falls from 56.6 A to 50.64 A.
- An 11 kW motor at 0.8 with 7.5 A no-load current can take 4.68 kvar at most, which lifts it to 0.939 and cuts the line current to 18.79 A. Correct the rest at the board.
- A 55 kW motor at 0.75 with 30 A no-load current can take 18.71 kvar at most, which lifts it to 0.867 and cuts the line current to 101.78 A.
Limits
The tool does not assess harmonics unless you enter the THDi. Switch each step with a device rated for capacitors. The tool does not model resonance with the supply.
See also: Power factor and reactive power, Power factor correction for a 250 kW factory and Three phase power.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
He rahi pēhea te capacitor ka taea e au te whakauru ki tētahi mōtā?
Kaua e neke atu i te 90 % pea o te kvar kore-uta o te mōtā, he ture mahi tēnei. Ko te mea nui ake ka whakaoho i te mōtā ake i muri i tōna katinga. Whakaritea te taputapu ki te Mōtā kotahi, ka whakauru i te iahiko kore-uta.
Me pēhea te tātai i te kvar?
Ka kimihia e te taputapu te reactive power i te power factor o nāianei me te power factor whāinga, ā, i runga anō i te real power. Ko te rerekētanga te kvar me whakarato e te bank. Kātahi ka whakapiki ki ngā hīkoi katoa o te bank.
He aha te heke o te iahiko i muri i te correction?
Ka mau tonu te real power, engari ka whakarato te bank i te reactive power i te wāhi. Nō reira he iti iho te apparent power ka kawea e te puna hiko. Ka heke te iahiko i te tauritenga, ā, ko te kVA ka wetekina he kaha kua tukuna.
Āhea e hiahiatia ai he bank detuned?
Ka tango ngā drive, ngā rectifier me ngā LED driver i ngā iahiko harmonic. Ka taea e ngā capacitor māmā te haruru me te puna hiko, ā, ka whakanui i a rātou. Hei ture ringa, ki runga ake i te 10 % THDi, whakauruhia he bank detuned me ngā reactor raupapa. Ki runga ake i te 20 %, whiwhia he rangahau harmonic.
He aha te tikanga o te resonance order?
Ka hanga te capacitor bank me te puna hiko i tētahi ara iahiko tōtika. Ko te raupapa he pūtakere pūtahi o te taumata hapa ki runga i te kvar o te bank. I tata ki te harmonic 5, 7, 11, 13 rānei, ka whakatūpato te taputapu ki a koe.
Ngā tauira mahi
Kōrero o muri
Ngā Clause me ngā Table e pānuitia ana e tēnei taputapu
Ngā taputapu hononga
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