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Inrush Current Formula:
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Inrush current is the maximum instantaneous input current drawn by an electrical device when first turned on. This initial surge of current is typically much higher than the steady-state current and occurs due to the charging of capacitors, transformers, and other reactive components.
The calculator uses the inrush current formula:
Where:
Explanation: This formula calculates the initial surge of current when a circuit is first energized, based on Ohm's Law.
Details: Calculating inrush current is essential for proper circuit protection, preventing nuisance tripping of breakers, selecting appropriate fuses and circuit breakers, and ensuring the longevity of electrical components.
Tips: Enter voltage in volts and resistance in ohms. Both values must be positive numbers greater than zero for accurate calculation.
Q1: Why is inrush current higher than steady-state current?
A: Inrush current is higher due to the initial charging of capacitors and the magnetization of transformer cores, which creates a temporary low-impedance path.
Q2: How long does inrush current typically last?
A: Inrush current typically lasts from a few milliseconds to several cycles of the AC waveform, depending on the circuit components.
Q3: What factors affect inrush current?
A: Factors include capacitor size, transformer characteristics, supply voltage, and the point in the AC cycle when the circuit is energized.
Q4: How can inrush current be limited?
A: Inrush current can be limited using NTC thermistors, series resistors, soft-start circuits, or specialized inrush current limiters.
Q5: Is this formula applicable to all types of circuits?
A: This basic formula works for resistive circuits. For circuits with significant inductive or capacitive components, more complex calculations may be needed.