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Inrush Current Limiter Formula:
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An inrush current limiter resistor is used to limit the initial surge of current that occurs when power is first applied to a circuit, particularly in capacitive loads. This protects components from damage due to excessive current.
The calculator uses Ohm's Law to determine the appropriate resistor value:
Where:
Explanation: The resistor value is calculated by dividing the supply voltage by the maximum desired inrush current.
Details: Inrush current limiting is crucial for protecting power supplies, capacitors, and other components from damage caused by excessive initial current flow when a device is first powered on.
Tips: Enter the supply voltage in volts and the maximum allowable inrush current in amps. Both values must be positive numbers.
Q1: What types of circuits need inrush current limiting?
A: Circuits with large capacitive loads, power supplies, motor drives, and any application where initial current surge could damage components.
Q2: How do I choose the maximum inrush current?
A: Check component datasheets for maximum ratings. Typically, you want to stay well below the maximum ratings of your most sensitive component.
Q3: What about power dissipation in the resistor?
A: The resistor must be rated for the power dissipation (P = V²/R). Consider using NTC thermistors for high-power applications.
Q4: Are there alternatives to resistors for inrush limiting?
A: Yes, NTC thermistors are common as they provide high resistance when cold and lower resistance when warm, automatically reducing their limiting effect after startup.
Q5: What happens if I don't use an inrush current limiter?
A: Without proper limiting, components may fail prematurely, fuses may blow unnecessarily, or power supplies may go into protection mode.