1. What is Inrush Current?

Inrush current is the maximum instantaneous input current drawn by an electrical device when first turned on. It's typically much higher than the steady-state current and can cause issues like tripped breakers or damaged components if not properly managed.

2. How Does the Calculator Work?

The calculator uses the inrush current equation:

Where:

• \( I_{inrush} \) — Peak inrush current (A)
• \( V \) — Applied voltage (V)
• \( R_{eq} \) — Equivalent circuit resistance (Ω)

Explanation: The equation calculates the initial current surge based on Ohm's Law, before inductive or capacitive effects come into play.

3. Importance of Inrush Current Calculation

Details: Calculating inrush current is essential for proper circuit protection, component selection, and preventing nuisance tripping of protective devices.

4. Using the Calculator

Tips: Enter the applied voltage in volts and the equivalent resistance in ohms. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is inrush current higher than steady-state current?
A: Because initial resistance is often lower (before components heat up or magnetic fields establish) and capacitors appear as short circuits initially.

Q2: How can I reduce inrush current?
A: Common methods include using NTC thermistors, soft-start circuits, or staggered power-up sequences.

Q3: Is this calculation accurate for all circuits?
A: This provides the resistive component. For circuits with significant inductance or capacitance, more complex calculations are needed.

Q4: What's typical duration of inrush current?
A: Typically lasts from a few milliseconds to several cycles, depending on the circuit characteristics.

Q5: How does this affect fuse selection?
A: Fuses must withstand the brief inrush current while still protecting against sustained overcurrents, often requiring slow-blow types.