Calculateur de Courant de Défaut à la Terre
Calculez le courant de défaut à la terre dans un système électrique.
DOL=6-8x, Soft start=2-3x, VFD=1-1.5x
Full Load Current (FLA)
11.7 A
Full Load Current (FLA) vs Motor Horsepower
Formule
Motor Starting Current
Electric motors draw significantly more current during startup than at full speed. This inrush can be 6-8 times the full-load current.
Formulas
FLA (3-phase) = HP x 746 / (sqrt(3) x V x Eff x PF)
Starting Current = FLA x Multiplier
Starting Methods and Multipliers
Exemple Résolu
10 HP motor, 480 V 3-phase, 90% efficient, PF 0.85, DOL start (6x).
- 01Motor watts: 10 x 746 = 7,460 W
- 02FLA: 7460 / (1.732 x 480 x 0.90 x 0.85) = 7460 / 635.6 = 11.7 A
- 03Starting current: 11.7 x 6 = 70.4 A
- 04Starting kVA: 70.4 x 1.732 x 480 / 1000 = 58.5 kVA
Questions Fréquentes
Why is starting current so high?
At standstill, the motor's back-EMF is zero, so impedance is very low. As the motor accelerates, back-EMF rises and current drops to normal.
How does inrush affect the electrical system?
Large inrush can cause voltage dips, nuisance breaker trips, and flicker. Size feeders and breakers for the starting current.
When should I use a soft starter or VFD?
For motors above 10 HP on weak supplies, frequent starts, or when gradual acceleration is beneficial for the driven equipment.
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