1. What is Inrush Current?

Inrush current is the instantaneous high input current drawn by a power supply or electrical device when first turned on. For capacitors, this occurs due to the rapid charging of the capacitor when voltage is first applied.

2. How Does the Calculator Work?

The calculator uses the inrush current formula:

Where:

• \( I_{inrush} \) — Inrush current in amps
• \( V \) — Applied voltage in volts
• \( ESR \) — Equivalent Series Resistance in ohms

Explanation: The equation calculates the peak current that flows when a capacitor is initially charged, determined by the voltage and the capacitor's internal resistance (ESR).

3. Importance of Inrush Current Calculation

Details: Calculating inrush current is crucial for designing circuits that can handle the initial surge, selecting appropriate fuses and circuit breakers, and preventing damage to components.

4. Using the Calculator

Tips: Enter the applied voltage in volts and the capacitor's ESR in ohms. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is inrush current important?
A: High inrush currents can trip circuit breakers, blow fuses, or damage components if not properly accounted for in the design.

Q2: How can I reduce inrush current?
A: Common methods include using inrush current limiters (NTC thermistors), soft-start circuits, or series resistors.

Q3: Does inrush current affect capacitor lifespan?
A: Repeated high inrush currents can degrade capacitors over time, especially electrolytic capacitors.

Q4: Is this calculation accurate for all capacitor types?
A: The basic formula works for most types, but actual inrush may be affected by additional factors like wiring inductance.

Q5: What's the difference between ESR and DCR?
A: ESR (Equivalent Series Resistance) includes all resistive losses in a capacitor, while DCR (DC Resistance) typically refers to inductor resistance.