Motor Starting Current Calculator
Calculate motor starting current (inrush current) for single-phase and three-phase electric motors. Determine full load current, starting power, and protection requirements.
Step 1: Motor Specifications
Understanding Motor Specifications
Motor starting current (inrush current) is typically 5-7 times the full load current. Larger motors may have lower starting current multiples due to design considerations.
Step 2: Starting Parameters
Starting Current Reduction
Different starting methods reduce starting current: Star-Delta (33%), Soft Starters (up to 70%), VFDs (controlled ramp-up). This affects protection sizing and voltage dip.
Motor Starting Current Results
Starting Current (Inrush)
Starting Method Comparison
| Starting Method | Starting Current | % of DOL | Torque | Application |
|---|
Motor Current Formulas
Three-Phase Full Load Current
I = P × 1000 / (√3 × V × PF × Efficiency)
Where: P in kW, V in Volts, PF = Power Factor
Single-Phase Full Load Current
I = P × 1000 / (V × PF × Efficiency)
Where: P in kW, V in Volts
Starting Current (Inrush)
Istart = IFLC × Starting Multiplier
Typical multipliers: 5-7× for small motors, 3-5× for large motors
Starting Apparent Power
Sstart = √3 × V × Istart / 1000 (Three Phase)
Sstart = V × Istart / 1000 (Single Phase)
Result in kVA
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