1. What is Inrush Current?

Inrush current is the instantaneous high input current drawn by a circuit when first turned on, particularly in capacitive circuits. This occurs due to the initial charging of capacitors when voltage is first applied.

2. How Does the Calculator Work?

The calculator uses Ohm's Law for the inrush current:

Where:

• \( I \) — Inrush current (Amperes)
• \( V \) — Applied voltage (Volts)
• \( R \) — Series resistance (Ohms)

Explanation: The series resistor limits the maximum current that can flow when charging the capacitor initially.

3. Importance of Inrush Current Calculation

Details: Calculating inrush current helps in selecting appropriate components that can handle the initial surge and designing circuits that won't trip power supplies or breakers during startup.

4. Using the Calculator

Tips: Enter voltage in volts and resistance in ohms. All values must be positive numbers. The calculator will compute the peak inrush current.

5. Frequently Asked Questions (FAQ)

Q1: Why is inrush current higher than steady-state current?
A: Because capacitors initially act like short circuits when uncharged, drawing maximum current until they begin to charge up.

Q2: How can I reduce inrush current?
A: By increasing the series resistance, using inrush current limiters (NTC thermistors), or implementing soft-start circuits.

Q3: Is this calculation accurate for all capacitor types?
A: This gives the theoretical maximum current. Real-world values may be slightly lower due to ESR and other factors.

Q4: What happens if inrush current is too high?
A: It can damage components, cause voltage sags, trip circuit breakers, or reduce the lifespan of switches and contacts.

Q5: Does this apply to AC circuits as well?
A: The basic principle applies, but AC circuits have additional considerations like frequency and phase angle.