PF Capacitor Bank for a Target Resonant Order
The PF capacitor bank that puts the parallel resonance at a target order.
Example
You enter
- Short-circuit power at the capacitor bus, utility + transformer combined (MVA) 200
- Target resonant order (e.g. 4.7 to sit just below the 5th) 4.7
You get
- Capacitor bank that resonates at the target 9.054 MVAR
Checked against published worked examples from: Eaton Corporation (Cutler-Hammer).
Details, formula, and sources
ScopeMVAR_cap = MVA_sc / h^2. A 200-MVA bus resonates at an order of 4.7 (just below the 5th) with a ~9.05 MVAR bank; a smaller bank walks the resonance up onto the 5th and a bigger one moves it lower, so below a harmonic the figure is a minimum and above one it is a maximum. Split into smaller banks or add a detuning reactor for more correction. A screening aid; a harmonic study governs.
Formula or tableMVAR_cap = MVA_sc / h_target^2, the parallel-resonance relation h = sqrt(MVA_sc / MVAR_cap) solved for the bank (the maximum bank that keeps the resonant order at or above the target).
Source and editionParallel-resonance order of a power-factor capacitor bank (IEEE 519 / IEEE 1531) solved for the bank, first-principles, by name; a harmonic study governs.
Free accessThe h = sqrt(MVA_sc / MVAR_cap) resonance relation is a published first-principles result; the bus short-circuit level comes from the system data.
What governsEstimate. AHJ and licensed professional govern.
API field namesshort_circuit_mva, target_resonant_order, max_cap_bank_mvar
- Bank ceiling MVAR_cap = MVA_sc / h_target^2 keeps the resonant order at or above the targetIEEE 1531
- Bigger bank, lower order a larger capacitor bank lowers the resonant order toward the strong low harmonicsIEEE 519
- Idealized ignores load and resistive damping; a detuning reactor or harmonic study is the fixscope of this tile