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. This occurs due to the initial charging of capacitors and building up of magnetic fields in inductive components.

2. How Does the Calculator Work?

The calculator uses the inrush current formula:

Where:

• \( I_{inrush} \) — Inrush current (amps)
• \( V \) — Input voltage (volts)
• \( R_{series} \) — Series resistance (ohms)

Explanation: The equation calculates the peak current that flows when a capacitor is initially connected to a voltage source through a 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 connected devices.

4. Using the Calculator

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

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 NTC thermistors, series resistors, soft-start circuits, or staggered turn-on of components.

Q3: Does this calculation account for capacitor ESR?
A: This simple calculation assumes ideal components. For more precision, you would need to include the equivalent series resistance (ESR) of the capacitor.

Q4: What's the difference between inrush current and steady-state current?
A: Inrush current is the temporary peak current during startup, while steady-state current is the normal operating current after initial transients have settled.

Q5: When is this calculation most applicable?
A: This calculation is most accurate for simple RC circuits where the series resistance dominates the current limiting.