Power factor correction calculator
Hanapin ang capacitor kvar para itaas ang power factor.
Reads AS/NZS 3000:2018.
Subukan ang isang job 10
Nilalagyan ng halimbawang value ang bawat job. Palitan ang mga ito ng sarili mong value.
- 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.
Mga input
Worked example gamit ang mga default na input.
- Itama
- Isang load o isang board
- Mga phase
- Three phase
- Voltage
- 400 V
- Yunit ng load
- kW
- Load
- 100
- Kasalukuyang power factor
- 0.75
- Target power factor
- 0.95
- Bank step
- 25 kvar
- Current harmonic distortion (THDi)
- 0 %
- Fault level sa bank
- 0 MVA
Kailangan ng correction
55.32kvar
- Naka-install na bank
- 3 × 25kvar
- Power factor kasama ang bank
- 0.991
- Current bago
- 192.45A
- Current pagkatapos
- 145.59A
- Nailabas na kapasidad
- 32.47kVA
- Mga konduktor ng bank, hindi bababa sa
- 146.14A
Design aid lang ang resultang ito. I-verify ito laban sa kasalukuyang standard.
Mga hakbang ng kalkulasyon
- Real power100kW
- Reactive power sa kasalukuyang power factor88.19kvar
- Reactive power sa target na power factor32.87kvar
- Kailangan ng correctionResulta55.32kvar
- Mga bank step
3 × 25 kvar
- Power factor kasama ang bank0.99
- Current bago192.45A
- Current pagkatapos145.59A
- Nailabas na kapasidad32.47kVA
- Rated current ng bank108.25A
- Pinakamababang capacity ng bank conductor, 135 %146.14A
AS/NZS 3000:2018 Cl 4.15.2.3
Tungkol sa calculator na ito
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.
Mga tanong
Design aid ang resulta. I-verify ito laban sa kasalukuyang standard.
Gaano kalaking capacitor ang puwede kong ilagay sa motor?
Hindi hihigit sa mga 90 % ng no-load kvar ng motor, bilang rule of thumb. Kapag mas malaki, puwedeng mag-self-excite ang motor pagkatapos itong i-switch off. Itakda ang tool sa One motor at ilagay ang no-load current.
Paano kinakalkula ang kvar?
Hinahanap ng tool ang reactive power sa kasalukuyang power factor at sa target, parehong mula sa real power. Ang pagkakaiba ay ang kvar na dapat ibigay ng bank. Pagkatapos, nire-round up ito sa buong bank step.
Bakit bumababa ang current pagkatapos ng correction?
Nananatiling pareho ang real power, pero ang bank ang nagbibigay ng reactive power sa site. Kaya mas kaunting apparent power ang dinadala ng supply. Bumababa ang current nang proporsyonal, at ang kVA na napalaya nito ay ang released capacity.
Kailan ko kailangan ang detuned bank?
Ang drives, rectifiers at LED drivers ay humihila ng harmonic currents. Ang plain capacitors ay puwedeng mag-resonate sa supply at palakasin ang mga ito. Bilang panuntunan, kapag higit sa humigit-kumulang 10 % THDi, maglagay ng detuned bank na may series reactors. Kapag higit sa 20 %, kumuha ng harmonic study.
Ano ang ibig sabihin ng resonance order?
Ang capacitor bank at ang supply ay bumubuo ng tuned circuit. Ang order ay ang square root ng fault level na hinati sa bank kvar. Kapag malapit sa ika-5, ika-7, ika-11 o ika-13 na harmonic, binabalaan ka ng tool.
Mga worked example
Background
Mga clause at table na binabasa ng tool na ito
Mga kaugnay na tool
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