How do I calculate motor capacitor size?

For a run capacitor: C ≈ P/(2π×f×V²×η×cosφ) × 10⁶ μF. A rough rule of thumb is 30-50 μF per HP for run capacitors and 100-150 μF per HP for start capacitors.

What is the difference between start and run capacitors?

Start capacitors are electrolytic, high-value (70-400 μF), used only during startup then disconnected by a centrifugal switch. Run capacitors are film type, lower value (5-60 μF), and remain in circuit continuously.

What happens if the capacitor is too small?

Too small: motor may not start (low starting torque), may overheat, reduced efficiency. Too large: excessive current in auxiliary winding, overheating, possible winding damage.

Can I use a higher voltage capacitor?

Yes, using a capacitor with a higher voltage rating is safe. However, never use a lower voltage rating than required — typically 1.5× the supply voltage for safety margin.

What are PSC and CSIR motors?

PSC (Permanent Split Capacitor) uses a run capacitor only — simple but lower starting torque. CSIR (Capacitor Start Induction Run) adds a start capacitor with centrifugal switch for higher starting torque, typical for compressors and pumps.

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Calculadora de condensadores para motores

Calcule los valores de los condensadores de arranque y marcha para motores monofásicos. C = I / (2πfV). Estimaciones basadas en la potencia, el voltaje y la frecuencia del motor.

Condensador de arranqueCondensador de marchaMonofásico

Resultados

Condensador de marcha (estimado)

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Condensador de arranque (estimado)

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Corriente del motor

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Voltaje mínimo nominal del condensador

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Fórmula del condensador

Los condensadores de arranque suelen tener un valor de 3 a 5 veces el del condensador de marcha. Los condensadores de marcha usan dieléctrico de película; los de arranque usan electrolítico.

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