1. What is a DC Inrush Current Limiter?

A DC inrush current limiter is a resistor used to reduce the initial surge of current when a DC power supply is first connected to a capacitive load. This protects components from damage due to excessive current.

2. How Does the Calculator Work?

The calculator uses the simple resistance formula:

Where:

• \( R \) — Limiting resistance in ohms (Ω)
• \( V \) — Supply voltage in volts (V)
• \( I_{max} \) — Maximum allowable inrush current in amps (A)

Explanation: The resistor value is calculated to limit the initial current to the specified maximum value when power is first applied.

3. Importance of Inrush Current Limiting

Details: Inrush current limiting protects power supplies, capacitors, and other components from damage due to excessive current when first powered on. It also prevents voltage sag in the power supply.

4. Using the Calculator

Tips: Enter the power supply voltage and the maximum allowable inrush current. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What type of resistor should I use?
A: Use a power resistor rated for at least 2-3 times the calculated power dissipation (P = V²/R).

Q2: Can I use an NTC thermistor instead?
A: Yes, NTC thermistors are commonly used as they provide high initial resistance that decreases as they heat up.

Q3: How do I choose the maximum inrush current?
A: Check the specifications of your components (capacitors, power supply, etc.) for maximum surge current ratings.

Q4: Should I bypass the resistor after startup?
A: For high-power applications, you may want to use a relay or MOSFET to bypass the resistor after capacitors charge.

Q5: What about inductive loads?
A: This calculator is for capacitive loads. Inductive loads require different considerations for inrush current.