1. What is Inrush Current?

Inrush current is the maximum instantaneous input current drawn by an electrical device when first turned on. For capacitors, this occurs during the initial charging phase when the capacitor appears as a short circuit.

2. How Does the Calculator Work?

The calculator uses Ohm's Law:

Where:

• \( I \) — Inrush current (amperes)
• \( V \) — Voltage (volts)
• \( R \) — Resistance (ohms)

Explanation: When a capacitor is initially connected to a power source, it behaves like a short circuit, and the current is limited only by the resistance in the circuit.

3. Importance of Inrush Current Calculation

Details: Calculating inrush current is crucial for selecting appropriate circuit protection devices, preventing damage to components, and ensuring reliable system operation.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why is inrush current higher than steady-state current?
A: Inrush current is higher because capacitors initially appear as a short circuit, drawing maximum current until they begin to charge.

Q2: How can inrush current be limited?
A: Inrush current can be limited using series resistors, NTC thermistors, or specialized inrush current limiter circuits.

Q3: Does capacitor size affect inrush current?
A: While the formula I = V/R suggests capacitance doesn't directly affect peak inrush current, larger capacitors may sustain the current for longer durations.

Q4: What are typical inrush current values?
A: Inrush current can be many times higher than normal operating current, sometimes 10-100 times greater depending on the circuit.

Q5: Are there safety concerns with inrush current?
A: Yes, high inrush currents can trip circuit breakers, damage contacts in switches and relays, and cause voltage dips in the power supply.