AUWiring

Capacitor resonance screen calculator

Screen an entered capacitor and source inductance record for resonant frequency and harmonic-order proximity in Australian power-quality review.

  • Calculator
  • Power quality
  • Australia
Use a PFC stage, switchboard, feeder or harmonic-review reference.
uF
Enter the capacitance value used for this screening record.
mH
Enter the source or equivalent inductance basis for the screen.
Hz
Australian low-voltage records normally use 50 Hz unless the project record says otherwise.
order
Enter the harmonic order being screened against this record.
order
Enter the harmonic-order distance used as the screening band.
Name the project, supplier or engineering basis for the review band.
f_r = 1 / (2 x pi x sqrt(L x C)); h = f_r / f_system
  • Capacitance and inductance are user-entered source-record values.
  • The review band is a user-entered screening band, not a product or network decision.
  • This screening worksheet does not perform detuned reactor selection or a harmonic study.
Formula variables
VariableMeaningUnitUse
CCapacitanceFEntered capacitance converted from microfarads.
LInductanceHEntered inductance converted from millihenry.
f_rResonant frequencyHzLC resonant frequency from entered values.
f_systemSystem frequencyHzEntered supply frequency, commonly 50 Hz in Australian low-voltage records.
hHarmonic orderorderResonant frequency divided by system frequency.
review_hReview harmonic orderorderUser-entered harmonic order being screened.
bandReview bandorderUser-entered harmonic-order distance used for the screen.
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Capacitor resonance screen calculator technical guide

Screen an entered capacitor and source inductance record for resonant frequency and harmonic-order proximity in Australian power-quality review.

Use this calculator when a power-factor-correction or power-quality note needs a simple LC resonance screen. It converts entered capacitance, entered inductance and system frequency into resonant frequency and harmonic order.

This is a screening worksheet. It does not select a detuned reactor, choose a capacitor product, model switching behaviour or replace a harmonic study. Its value is making the entered LC basis and review band visible.

Screening Worksheet Boundary

What the screen includes
ItemIncluded in the arithmeticBoundary to keep separate
CapacitanceEntered microfarads converted to farads.Product tolerance and stage configuration remain source records.
InductanceEntered millihenry converted to henry.Source impedance method and study assumptions remain external.
FrequencyEntered system frequency.Australian records commonly use 50 Hz but the project record controls the value.
Review harmonicUser-entered harmonic order.The calculator does not choose the project review target.
Review bandUser-entered harmonic-order distance.Supplier and engineering practice can override the screen.

Result Interpretation

Resonance outputs
OutputMeaningPractical reading
Resonant frequencyLC frequency from entered capacitance and inductance.Main screening result.
Harmonic orderResonant frequency divided by system frequency.Converts Hz into a power-quality review language.
Nearest harmonicRounded harmonic order.Quick pointer only, not a study result.
Review band resultWhether the order is inside the entered band.Screening flag for supplier or engineering review.

When the calculated order sits near the entered review harmonic, keep the result as a prompt for further review. It should not be turned into product selection or equipment action by itself.

Boundary With Related Calculators

Which page owns the question
QuestionCorrect ownerInput basis
What kVAr correction is needed?Power factor correction calculatorkW and power-factor values.
Which entered capacitor stages meet a target?Capacitor bank staging calculatorRequired kVAr and user-entered stage sizes.
What harmonic distortion was measured?Harmonic THD calculatorFundamental and harmonic RMS magnitudes.
What LC frequency follows from entered C and L?Capacitor resonance screen calculatorCapacitance, inductance and frequency.

Worked Records

Capacitor resonance examples
SituationInputsResult patternInterpretation
PFC stage near seventh harmonic20 uF, 10 mH, 50 Hz, seventh-order review355.88 Hz, order 7.12Inside the entered review band.
Fifth-harmonic comparisonSame LC values, fifth-order reviewOrder 7.12, outside the fifth-order bandUseful contrast while staying a screen.
Alternative 50 Hz record10 uF, 6 mH, 50 HzHigher harmonic-order estimateCarry into supplier or engineering review.

Stop Points

  • Capacitance or inductance is guessed without a source record.
  • The result is being used to choose a reactor, capacitor stage or protection setting.
  • The review band has no project, supplier or engineering basis.
  • Measured harmonic levels, damping, switching and load state are needed.
  • DNSP, supplier, manufacturer or project requirements provide a different review basis.

PFC stage near seventh harmonic

A screening note checks entered capacitance and source inductance against a seventh-harmonic review band.

Reference
PFC-RESONANCE-01
Capacitance
20 uF
Inductance
10 mH
System frequency
50 Hz
  1. Resonant frequency355.88 Hz
  2. Harmonic order7.12
  3. Nearest harmonic7
Resonant frequency355.88 Hz

Equivalent to harmonic order 7.12 on the entered system frequency.

The calculated order is inside the entered band, so it should be treated as a screening flag for review.

  • Capacitance and inductance are entered by the user.
  • Frequency is 50 Hz for the record.
  • The review band is not a universal threshold.

Fifth-harmonic comparison

The same LC values are compared with a fifth-harmonic review order.

Reference
PFC-FIFTH-CHECK
Capacitance
20 uF
Inductance
10 mH
System frequency
50 Hz
  1. Resonant frequency355.88 Hz
  2. Harmonic order7.12
  3. Nearest harmonic7
Resonant frequency355.88 Hz

Equivalent to harmonic order 7.12 on the entered system frequency.

The result is outside the entered fifth-harmonic band, while still remaining a screening result.

  • The LC inputs are unchanged.
  • The review target changed.
  • A harmonic study is still separate.

Alternative 50 Hz screening record

A smaller capacitance and inductance record shows a higher resonant order.

Reference
PFC-ALT-STAGE
Capacitance
10 uF
Inductance
6 mH
System frequency
50 Hz
  1. Resonant frequency649.75 Hz
  2. Harmonic order12.99
  3. Nearest harmonic13
Resonant frequency649.75 Hz

Equivalent to harmonic order 12.99 on the entered system frequency.

The screening note gives a harmonic-order estimate to carry into supplier or engineering review.

  • Entered values are source-record values.
  • Supplier data may override the basis.
  • No product selection is performed.

Questions

Does this select a capacitor bank?

No. It screens entered LC values only. Product selection and supplier review remain separate.

Where should inductance come from?

Use a project, engineering, supplier or study source that belongs to the screening record.

Can this replace a harmonic study?

No. It is a screening worksheet and does not model site harmonics, damping, switching or network conditions.

Why is the review band entered by the user?

Different projects and supplier records use different screening bases, so the band must remain visible.