1. What is Inrush Current?

Inrush current is the instantaneous high current drawn by an electrical device when first turned on. For motors, this can be 6-8 times the full load current (FLA) and lasts only for a few cycles.

2. How Does the Calculator Work?

The calculator uses the inrush current formula:

Where:

• FLA — Full Load Amps (steady-state current)
• Inrush Multiplier — Typically 6-8 for motors (can be higher for some equipment)

Explanation: The multiplier accounts for the initial surge of current needed to overcome the motor's inertia and establish magnetic fields.

3. Importance of Inrush Current Calculation

Details: Calculating inrush current is critical for proper circuit breaker sizing, wire selection, and transformer capacity planning to prevent nuisance tripping or equipment damage during startup.

4. Using the Calculator

Tips: Enter the motor's full load current (FLA) in amps and the appropriate inrush multiplier (typically 6-8 for standard motors). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is inrush current higher than running current?
A: At startup, motors need extra current to overcome inertia, charge capacitors, and establish magnetic fields before settling to steady-state operation.

Q2: How long does inrush current last?
A: Typically 3-10 electrical cycles (50-200 milliseconds), though duration varies by motor size and design.

Q3: Can inrush current damage equipment?
A: Repeated high inrush currents can stress components. Proper circuit protection is needed to handle the temporary surge.

Q4: How can inrush current be reduced?
A: Methods include soft starters, variable frequency drives (VFDs), or star-delta starting configurations.

Q5: Do all motors have the same inrush multiplier?
A: No, high-efficiency motors often have higher inrush (8-12x), while some special designs may have lower inrush.