RLC impedance and resonance equations
Series circuits combine impedance while parallel circuits combine admittance.
XL = 2πfLXC = 1/(2πfC)Zseries = R + j(XL − XC)Yparallel = 1/R + j(1/XC − 1/XL)f0 = 1/(2π√LC)where:
- XL
- Inductive reactance[Ω]
- XC
- Capacitive reactance[Ω]
- f0
- Ideal resonance frequency[Hz]
Losses and parasitics determine real resonance magnitude and Q.
How to use the RLC Impedance and Resonance Calculator
Calculate series or parallel RLC reactance, impedance, admittance, current, phase angle, power factor, resonance frequency, and Q factor. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Ideal lumped R, L and C at one sinusoidal frequency Parallel mode uses separate R, L and C branches No winding resistance, ESR, saturation or parasitics A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Ideal lumped R, L and C at one sinusoidal frequency
- Parallel mode uses separate R, L and C branches
- No winding resistance, ESR, saturation or parasitics
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Resonance can create high current or component voltage; verify losses and ratings with real component data. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
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Assumptions
- Ideal lumped R, L and C at one sinusoidal frequency
- Parallel mode uses separate R, L and C branches
- No winding resistance, ESR, saturation or parasitics
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.
- Resonance can create high current or component voltage; verify losses and ratings with real component data.