Motor Starting Current Calculator

Calculate motor starting current, kVA, and power

Motor Starting Current Calculator

Compliant with IEC 60034 Standards

Results:

Starting Current (A): 0.00

Starting kVA: 0.00

Starting Power (kW): 0.00

Motor Slip Calculator
Star Delta Motor Current Calculator

How to Use the Calculator

AC Motor Calculation

  1. Select "AC" system type
  2. Choose "Single Phase" or "Three Phase"
  3. Enter Motor Rated Power (kW), Voltage (V), and Current (A)
  4. Input Starting Current Multiplier (e.g., 5-7 times rated current)
  5. Provide Power Factor (0-1) and Efficiency (%)

DC Motor Calculation

  1. Select "DC" system type
  2. Enter Motor Rated Power (kW), Voltage (V), and Current (A)
  3. Input Starting Current Multiplier (e.g., 5-7 times rated current)
  4. Provide Efficiency (%)
  5. Power factor is automatically set to 1 for DC

Understanding Multiplier

  1. The starting current multiplier indicates how many times the rated current the motor draws during startup.
  2. Typical values range from 5 to 7 for induction motors.
  3. Consult motor datasheet for precise values.

Motor Starting Current Fundamentals

Starting Current

Motor starting current, also known as inrush current, is the instantaneous current drawn by an electric motor at startup. It is significantly higher than the motor's full-load current.

  • Can be 5-10 times the rated current.
  • Causes voltage dips and stresses electrical components.
  • Important for circuit breaker and cable sizing.

Factors Affecting Starting Current

  • Motor design (e.g., NEMA design B, C, D)
  • Load type (e.g., high inertia loads)
  • Starting method (e.g., Direct Online, Star-Delta, Soft Starter)
  • Supply voltage and frequency

Calculation Formulas

Rated Current (AC Single Phase):
I_rated = (P_kW * 1000) / (V * PF * Eff / 100)

Rated Current (AC Three Phase):
I_rated = (P_kW * 1000) / (√3 * V * PF * Eff / 100)

Rated Current (DC Systems):
I_rated = (P_kW * 1000) / (V * Eff / 100)

Starting Current:
I_start = I_rated * Multiplier

Starting kVA (AC Single Phase):
kVA_start = (I_start * V) / 1000

Starting kVA (AC Three Phase):
kVA_start = (√3 * I_start * V) / 1000

Starting kVA (DC Systems):
kVA_start = (I_start * V) / 1000

Starting Power (kW):
P_start = kVA_start * PF

Example Calculation

Three Phase AC Motor:

Rated Power: 10 kW

Rated Voltage: 400 V

Rated Current: 18 A

Starting Multiplier: 6

Power Factor: 0.85

Efficiency: 88 %

I_start = 18 A * 6 = 108 A

kVA_start = (√3 * 108 A * 400 V) / 1000 = 74.83 kVA

P_start = 74.83 kVA * 0.85 = 63.61 kW

Starting Current = 108.00 A | Starting kVA = 74.83 kVA | Starting Power = 63.61 kW

Related Motor Calculators

Star Delta Motor Cable Size Calculator

Calculate the appropriate cable size for star-delta motor connections.

Try Calculator

Motor Torque Calculator

Determine the torque produced by an electric motor based on power and speed.

Try Calculator

Motor Current Calculator

Calculate the full-load current of single-phase and three-phase motors.

Try Calculator