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 initial charging of the capacitor when voltage is first applied.

2. How Does the Calculator Work?

The calculator uses the inrush current formula:

Where:

• \( I_{peak} \) — Peak inrush current (A)
• \( V \) — Applied voltage (V)
• \( ESR \) — Equivalent series resistance (Ω)

Explanation: The equation shows that the peak inrush current is directly proportional to the applied voltage and inversely proportional to the equivalent series resistance.

3. Importance of Inrush Current Calculation

Details: Calculating inrush current is crucial for designing proper circuit protection, selecting appropriate components, and preventing damage to power supplies and capacitors.

4. Using the Calculator

Tips: Enter voltage in volts and ESR in ohms. Both values must be positive numbers greater than zero.

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 higher ESR capacitors.

Q3: Does capacitor value affect inrush current?
A: While capacitance doesn't appear in the peak current formula, larger capacitors will typically have longer inrush durations.

Q4: What's typical ESR for capacitors?
A: ESR varies by capacitor type (electrolytic, ceramic, etc.) and value, ranging from milliohms to several ohms.

Q5: Is this calculation valid for AC circuits?
A: This formula gives the initial peak current. For AC, additional factors like frequency and phase angle must be considered.